JP2007073763A - Semiconductor device and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique capable of improving the connection reliability between a bonding pad and a ball in primary bonding and the connection reliability between a lead and a wire in secondary bonding.
A semiconductor chip is disposed on a tab and inner leads are formed around the tab. The tip of the inner lead 13 (tip on the side close to the tab 14) 13a is inclined. The bonding pads 16 formed on the semiconductor chip 15 and the inner leads 13 are connected via balls 17 and wires 18. The inner lead 13 and the wire 18 are crimped at an inclined portion provided in the inner lead 13. The angle of inclination provided on the inner lead 13 is set to a range of 3 degrees to 15 degrees, for example.
[Selection] Figure 5

Description

  The present invention relates to a semiconductor device and a manufacturing technology thereof, and more particularly to a semiconductor device using a lead frame and a technology effective when applied to the manufacturing thereof.

  Japanese Patent Application Laid-Open No. 11-284017 (Patent Document 1) discloses a technique capable of preventing the detachment of a wire that occurs during wire bonding. Specifically, the leading edge portion of the heater plate on which the leading end portion of the lead located around the island is placed has an upward or downward slope.

Japanese Patent Application Laid-Open No. 7-37940 (Patent Document 2) discloses a technique capable of fixing a lead fine wire to an external lead with sufficient mechanical strength. Specifically, a thick presser part and a thin post projecting from the presser part are provided at one end of the external lead. The post protruding from the presser portion is configured to be inclined with respect to the bottom surface of the presser portion.
Japanese Patent Laid-Open No. 11-284017 Japanese Unexamined Patent Publication No. 7-37940

  As a process for manufacturing a semiconductor device, there is a process (wire bonding process) of electrically connecting a semiconductor chip arranged on a tab and a lead arranged around the tab using a wire. In this wire bonding step, primary bonding is performed by heat-pressing a ball formed by melting the tip of a wire made of a gold wire on a bonding pad of a semiconductor chip. Next, after the wire is moved onto the lead, the lead and the wire are thermocompression bonded to perform secondary bonding. In this way, the bonding pads on the semiconductor chip and the leads are electrically connected using the wires.

  In recent years, with the reduction in the size of a semiconductor chip, the interval between bonding pads formed on the semiconductor chip has also been reduced. When connecting the semiconductor chip and the lead with a wire, a bonding tool called a capillary 1 as shown in FIG. 1 is used. As the bonding pad interval is reduced, the tip 1a of the capillary 1 is connected. The size also needs to be reduced so as not to interfere with adjacent bonding pads.

  However, when the tip 1a of the capillary 1 is reduced, there is a problem that when the wire is crimped onto the lead by heat and ultrasonic waves, the crimping area of the wire is reduced, and the crimping strength of the wire is reduced or peeled off. . That is, there is a problem in that the pressure bonding strength at the time of performing the secondary bonding for connecting the wire on the lead is lowered.

  Therefore, in order to compensate for the reduction in the crimping area between the lead and the wire, it is conceivable to increase the crimping strength by increasing the thickness of the crimping part between the lead and the wire. Increasing the thickness of the crimping part can be realized by giving an angle α to the tip 1a of the capillary 1 shown in FIG. Even if the size of the semiconductor chip is further reduced, it is possible to further increase the thickness of the crimping portion by increasing the angle α of the tip 1a of the capillary 1.

  However, if the angle α of the tip 1a of the capillary 1 is too large, as shown in FIG. 3, the ultrasonic wave and the load that presses the ball 3 during the primary bonding in which the ball 3 is pressed onto the bonding pad 2 are Escape to the outside of 3. For this reason, an alloy layer (for example, an Al—Au layer) is formed on the outer periphery of the ball 3 at the boundary between the bonding pad 2 and the ball 3, whereas the center of the ball 3 (at the tip 1 a of the capillary 1 is formed). An alloy layer (for example, an Al—Au layer) is less likely to be formed under the opening. Therefore, since an alloy layer is not formed on the entire boundary between the bonding pad 2 and the ball 3, there is a problem that the bonding strength between the bonding pad 2 and the ball 3 is lowered and the ball 3 is peeled off from the bonding pad 2. Furthermore, if the angle α of the tip 1a of the capillary 1 is made too large, the tip 1a of the capillary 1 functions as a wedge, and the wire connected to the lead is connected at the tip 1a of the capillary 1 during secondary bonding. The problem of disconnection also occurs.

  Such a problem becomes prominent due to the miniaturization of semiconductor chips. For example, when the wire diameter is φ = 20 μm or less, the pulling strength of the wire decreases, and thus the above-described problem becomes apparent. In other words, it can be said that the problem becomes apparent when the bonding pad spacing is 50 μm or less.

  An object of the present invention is to provide a technique capable of improving the connection reliability between a bonding pad and a ball in primary bonding and the connection reliability between a lead and a wire in secondary bonding.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

  A method of manufacturing a semiconductor device according to the present invention includes (a) wire bonding between a bonding pad on a semiconductor chip and one end of a lead using a capillary having a tapered tip. Is performed in a state where one end of the lead is inclined.

  The semiconductor device according to the present invention includes (a) a semiconductor chip, (b) a lead disposed around the semiconductor chip, and (c) a wire for electrically connecting the semiconductor chip and one end of the lead. And (d) a resin that seals the semiconductor chip, the lead, and the wire, and one end portion of the lead to which the wire is connected is inclined.

  Among the inventions disclosed in the present application, effects obtained by typical ones will be briefly described as follows.

  Since wire bonding is performed in a state where one tip portion of the lead is inclined, the thickness of the crimped portion between the lead and the wire can be increased without increasing the angle α of the tip portion of the capillary. Therefore, since it is not necessary to increase the angle α of the tip of the capillary, the connection reliability between the bonding pad and the ball in primary bonding can be improved. On the other hand, since the lead and the wire can be connected at an angle that combines the inclination of the tip of the lead and the angle α of the tip of the capillary, the thickness of the crimped portion between the lead and the wire can be increased. The connection reliability between the lead and the wire can be improved.

  In the following embodiments, when it is necessary for the sake of convenience, the description will be divided into a plurality of sections or embodiments. However, unless otherwise specified, they are not irrelevant to each other. There are some or all of the modifications, details, supplementary explanations, and the like.

  Further, in the following embodiments, when referring to the number of elements (including the number, numerical value, quantity, range, etc.), especially when clearly indicated and when clearly limited to a specific number in principle, etc. Except, it is not limited to the specific number, and may be more or less than the specific number.

  Further, in the following embodiments, the constituent elements (including element steps and the like) are not necessarily indispensable unless otherwise specified and apparently essential in principle. Needless to say.

  Similarly, in the following embodiments, when referring to the shape, positional relationship, etc., of components, etc., unless otherwise specified, and in principle, it is considered that this is not clearly the case, it is substantially the same. Including those that are approximate or similar to the shape. The same applies to the above numerical values and ranges.

  Embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment, and the repetitive description thereof will be omitted.

(Embodiment 1)
FIG. 4 is a perspective view showing the appearance of the semiconductor device according to the first embodiment. The package form of the semiconductor device in the first embodiment is a QFP (Quad Flat Package). As shown in FIG. 4, the semiconductor device 10 according to the first embodiment is covered with a resin 11 having a rectangular parallelepiped shape, and outer leads 12 protrude from four side surfaces of the resin 11. The outer lead 12 has a structure bent into an L shape.

  FIG. 5 is a cross-sectional view showing a cross section taken along line AA of FIG. As shown in FIG. 5, the lead includes an outer lead 12 protruding from the side surface of the resin 11 and an inner lead 13 formed inside the resin 11. A tab 14 is formed in a central portion sandwiched between the left and right inner leads 13 (enclosed by a plurality of inner leads 13), and a semiconductor chip 15 is disposed on the tab 14. A circuit element such as a MISFET (Metal Insulator Semiconductor Field Effect Transistor) and wiring are formed on the semiconductor chip 15, and a bonding pad 16 is formed on the uppermost layer. A wire 18 is connected to the bonding pad 16 via a ball 17, and the wire 18 is connected to the inner lead 13.

  Here, one of the features of the present invention is that an inclination is provided at the tip of the inner lead 13 connecting the wire 18. Thereby, the connection reliability between the wire 18 and the inner lead 13 can be improved while ensuring the connection reliability between the bonding pad 16 and the ball 17. In recent years, the pitch of the bonding pads 16 formed on the semiconductor chip 15 has been reduced. For this reason, the wire 18 connected to the bonding pad 16 is also thinned. When the wire 18 is thinned, the connection area between the wire 18 and the inner lead 13 is reduced, the adhesive force between the wire 18 and the inner lead 13 is reduced, and a defect in which the wire 18 is peeled off from the inner lead 13 is likely to occur. Become. Therefore, an angle is applied to the tip of the capillary, which is a bonding tool. That is, the tip of the capillary is tapered. By doing in this way, since the thickness of the crimping part of the wire 18 and the inner lead 13 can be increased, connection reliability can be improved. However, if the tip end of the capillary is too angled, there arises a problem that the connection reliability between the bonding pad 16 and the ball 17 is deteriorated. This is because the ultrasonic wave and the load pushing the ball 17 escape to the outside of the ball 17. If the load that presses the ball 17 escapes to the outside of the ball 17, it is difficult to form an alloy layer at the center of the boundary between the bonding pad 16 and the ball 17. Accordingly, the bonding strength between the bonding pad 16 and the ball 17 is lowered, and the ball 17 is easily peeled off from the bonding pad 16. For this reason, the tip of the capillary cannot be angled too much. Therefore, in the first embodiment, the tip portion 13a of the inner lead 13 is provided with an inclination. Thus, the thickness of the crimped portion between the wire 18 and the inner lead 13 can be increased without making the tip of the capillary so angled. That is, since the wire 18 and the inner lead 13 can be crimped at an angle formed by combining the angle formed at the tip of the capillary and the angle due to the inclination of the inner lead 13, the thickness of the crimped portion is increased. The connection reliability between the wire 18 and the inner lead 13 can be improved. On the other hand, since the tip of the capillary is not so angled, the load that presses the ball 17 against the bonding pad 16 does not escape outward. For this reason, the connection reliability between the bonding pad 16 and the ball 17 can be improved. That is, according to the first embodiment, it is possible to improve the connection reliability between the wire 18 and the inner lead 13 while ensuring the connection reliability between the bonding pad 16 and the ball 17.

  The inclination provided in the inner lead 13 is formed so that the thickness of the inner lead 13 decreases as it goes to the tip end portion 13 a of the inner lead 13. By inclining in this way, the thickness of the crimping portion between the wire 18 and the inner lead 13 can be increased. Specifically, it is desirable that the inclination angle provided on the inner lead 13 is 3 degrees or more and 15 degrees or less. This is because if the angle of inclination provided on the inner lead 13 is less than 3 degrees, the thickness of the crimping portion cannot be sufficiently increased. On the other hand, if the angle of inclination provided in the inner lead 13 is greater than 15 degrees, the angle between the capillary and the inner lead 13 becomes too large, and the capillary functions as a wedge, and the wire 18 is cut. It is because there is a risk of being. Here, the angle formed at the tip of the capillary itself is not less than 3 degrees and not more than 15 degrees in consideration of the connectivity between the bonding pad 16 and the ball 17. Therefore, when connecting the wire 18 and the inner lead 13, the angle formed between the capillary and the inner lead 13 is the angle formed at the tip of the capillary itself and the tip of the inner lead 13. The angle of inclination is adjusted, and it is 6 degrees or more and 30 degrees or less. Within this angle range, the thickness of the crimping portion can be sufficiently increased, and cutting of the wire 18 due to the capillary functioning as a wedge can be prevented. From this, it can be seen that the inclination angle provided at the tip portion 13a of the inner lead 13 is preferably 3 degrees or more and 15 degrees or less.

  The inclination provided at the tip portion 13a of the inner lead 13 is formed in order to improve the connection reliability by increasing the thickness of the crimped portion between the wire 18 and the inner lead 13, so that the inner lead 13 Of these, it may be formed in a region connected to the wire 18. In other words, for example, silver plating is formed in the region connected to the wire 18 in the inner lead 13, so that an inclination is formed in the region plated with silver in the inner lead 13. Good. In addition, the region of the inner lead 13 connected to the wire 18 is, for example, in the range of about 500 μm from the tip of the inner lead 13, so that the region in the range of about 500 μm from the tip of the inner lead 13 is inclined. It can be said that it is sufficient.

  FIG. 6 is a top view showing the internal structure of the semiconductor device 10 shown in FIG. As shown in FIG. 6, a tab 14 is formed at the center of the semiconductor device 10, and leads are disposed around the tab 14. The lead is composed of an inner lead 13 covered with resin 11 and an outer lead 12 not covered with resin. A semiconductor chip 15 is mounted on the tab 14, and the semiconductor chip 15 and the inner lead 13 are electrically connected by a wire 18 made of, for example, a gold wire.

  Next, a method for manufacturing the semiconductor device according to the first embodiment will be described with reference to the drawings.

  First, as shown in FIG. 7, a lead frame is prepared. The lead frame is formed with a plurality of leads 21 and a tab 20 at the center surrounded by the leads 21. Of the leading end portions of the leads 21, the leading end portion (one leading end portion) 21 a on the side close to the tab 20 is provided with silver plating 22 and is inclined. The lead frame has a structure in which patterns such as tabs 20 and leads 21 are repeatedly formed in the vertical direction and the horizontal direction, and has a multiple structure on which a plurality of semiconductor chips are mounted.

  The lead frame including the tab 20 and the lead 21 is made of, for example, an alloy of iron and nickel or copper. And in order to bond a wire satisfactorily, the plating process is made and the silver plating 22 is formed in the upper surface of the front-end | tip part 21a of the lead 21. FIG. Furthermore, the top surface of the tip 21a is inclined. While this inclination is provided on the upper surface of the tip portion 21a, it is not provided on the lower surface of the tip portion 21a. That is, the tip 21a of the lead 21 becomes thinner as going to the tip. The reason why the inclination is not provided on the lower surface of the distal end portion 21a is that it is not necessary to provide an inclination on the lower surface of the distal end portion 21a, so that the lead frame can be placed on the stage 23 without a gap. In addition, it is necessary to keep the lower surface of the lead 21 and the tab 20 horizontal.

  A lead frame having such a configuration can be formed by, for example, pressing. That is, the tab 20 and the lead 21 are formed by press working with a mold, and the tip 21 a of the lead 21 is inclined. Thereafter, a silver plating 22 is formed on the tip 21a using a plating method, whereby a lead frame as shown in FIG. 7 can be obtained.

  Next, as shown in FIG. 8, the semiconductor chip 24 is mounted on the tab 20. The tab 20 and the semiconductor chip 24 are bonded using, for example, an Au paste or an epoxy resin adhesive. The semiconductor chip 24 is obtained by forming MISFETs and wirings in the state of a semiconductor wafer and then separating the semiconductor wafer into pieces by dicing. A bonding pad 25 made of, for example, aluminum is formed on the upper surface of the semiconductor chip 24.

  Subsequently, as shown in FIG. 9, the bonding pads 25 on the semiconductor chip 24 and the leads 21 are electrically connected through balls 26 and wires 27. At this time, the lead 21 is fixed by the presser jig 28. The pressing jig 28 is configured to press a region outside the region of the lead 21 where the silver plating 22 is applied. This is because the pressing jig 28 is contaminated when the region to which the silver plating 22 is applied is pressed. The ball 26 and the wire 27 that connect the bonding pad 25 and the lead 21 are formed using a capillary 29 that is a bonding tool (wire bonding process).

  Below, the detail of the wire bonding process mentioned above is demonstrated. First, as shown in FIG. 10, a ball 26 is formed using a capillary 29. An ultrasonic horn 30 that transmits ultrasonic waves is attached to the capillary 29, and a gold wire 31 is formed inside the capillary 29. The gold wire 31 is taken out from the tip of the capillary 29. Then, a discharge torch 32 is brought into contact with the gold wire 31 protruding from the tip of the capillary 29 to form a spherical ball 26 at the tip of the gold wire 31.

  Next, as shown in FIG. 11, the ball 26 formed at the tip of the gold wire 31 is pressed onto the bonding pad 25 formed on the semiconductor chip 24 (primary bonding). The state at this time is shown in FIG. As shown in FIG. 12, a ball 26 formed at the tip of the gold wire 31 on the bonding pad 25 is pressed using a capillary 29. Here, as shown in FIG. 12, since the angle α formed at the tip of the capillary 29 is not large, the load and ultrasonic waves that press the ball 26 by the capillary 29 do not escape outward. Accordingly, since a sufficient load is applied to the center portion of the ball 26, an alloy layer is formed at the center portion of the boundary between the bonding pad 25 and the ball 26. For example, since the bonding pad 25 is made of aluminum and the ball 26 is made of gold, an alloy layer made of aluminum and gold is formed at the boundary. Thereby, since the adhesive force of the bonding pad 25 and the ball | bowl 26 can be improved, it can prevent that the ball | bowl 26 peels off from the bonding pad 25. FIG. The angle α formed at the tip of the capillary 29 is set in a range sufficient to prevent the load pressed against the ball 26 by the capillary 29 from escaping to the outside. For example, the angle α is formed in the range of 3 to 15 degrees. Yes. From the viewpoint of preventing the load pressed against the ball 26 by the capillary 29 from escaping to the outside, the angle α formed at the tip of the capillary 29 is preferably 0 degrees. On the other hand, as will be described later, when connecting the lead 21 and the wire 27, it is desirable to form an angle α at the tip of the capillary 29 from the viewpoint of improving the adhesive force by increasing the thickness of the crimping portion. Therefore, in the first embodiment, the angle α is provided at the tip of the capillary 29 as long as the load pressed against the ball 26 by the capillary 29 and the ultrasonic waves do not escape to the outside as much as possible. However, the angle α provided at the tip of the capillary 29 is small in consideration of improving the bonding force between the bonding pad 25 and the ball 26 (adhesion force of primary bonding), so the wire 27 and the lead It cannot be said that the angle α has been set in such a manner that the point that increases the thickness at the time of bonding with the adhesive 21 is sufficiently taken into consideration.

  Next, as shown in FIG. 13, a wire 27 is formed from the ball 26 toward the lead 21 (looping), and as shown in FIG. 14, the wire 27 extending from the ball 26 is placed near the tip of the lead 21. Connect to (inner lead side) (stitch bond, secondary bonding). At this time, the lead 21 connecting the wire 27 is inclined. FIG. 15 is a cross-sectional view showing a state in which the wire 27 is crimped to the lead 21 to which the silver plating 22 is applied. As shown in FIG. 15, the lead 21 is inclined so that its thickness decreases as it goes to the tip. In FIG. 15, this inclined angle is an angle β. By forming the angle β in the lead 21, the angle between the wire 27 and the lead 21 is larger than the angle α provided at the tip of the capillary 29. That is, as shown in FIG. 15, the angle between the wire 27 and the lead 21 is an angle (α + β) larger than the angle α. Therefore, according to the first embodiment, the thickness at the crimping portion of the wire 27 and the lead 21 can be sufficiently increased. That is, since the thickness at the crimping portion between the wire 27 and the lead 21 can be sufficiently increased, even when the diameter of the wire 27 is reduced and the crimping area is reduced, the adhesive force can be ensured. Specifically, when the wire diameter is φ = 20 μm or less (in other words, when the bonding pad interval is 50 μm or less), a remarkable effect can be obtained and the adhesive force can be secured. Thus, according to the first embodiment, first, the angle α of the tip of the capillary 29 is reduced in consideration of the adhesive force between the bonding pad 25 and the ball 26 (adhesive force of primary bonding). Then, in order to compensate for a decrease in the adhesion force (adhesion force of secondary bonding) between the wire 27 and the lead 21 by reducing the angle α of the tip end portion of the capillary 29, an inclination (angle β) is applied to the tip end portion of the lead 21. Provided. As a result, even if the angle α of the tip end portion of the capillary 29 is reduced, it is possible to substantially increase the thickness of the crimped portion between the wire 27 and the lead 21. That is, according to the first embodiment, it is possible to improve the connection reliability between the wire 27 and the lead 21 while ensuring the connection reliability between the bonding pad 25 and the ball 26. For example, a sufficient effect can be obtained by setting the inclination angle β provided at the tip of the lead 21 to 3 degrees or more and 15 degrees or less. If the angle is less than 3 degrees, the effect is not obtained so much. If the angle is greater than 15 degrees, the capillary 29 itself functions as a wedge, and a new problem that the wire 27 is cut occurs.

  Next, as shown in FIG. 16, after the wire 27 and the lead 21 are pressure-bonded, the unnecessary wire 27 is cut (tail cut). Thereby, the bonding pad 25 and the lead 21 can be electrically connected via the ball 26 and the wire 27. In this way, one bonding pad 25 formed on the semiconductor chip 24 and one lead 21 can be connected. Thereafter, similarly, as shown in FIG. 17, all the bonding pads 25 formed on the semiconductor chip 24 and the leads 21 are connected. Thereby, a wire bonding process is complete | finished.

  Although the case where a gold wire is used as the wire 27 has been described in the first embodiment, for example, a gold wire to which palladium is added can be used as the material of the wire 27. By using a gold wire to which palladium is added, the bonding pad 25 made of aluminum and the ball 26 made of a gold wire to which palladium is added are connected, and the adhesive force can be further improved. This is because aluminum and a gold wire come into contact with each other, so that an alloy layer having a high bonding strength and a brittle alloy layer having a bonding strength lower than that are generated. If the ratio of gold to aluminum is high, an alloy layer with strong bonding strength is likely to be formed. However, if the ratio of gold is low, a brittle alloy layer is likely to be formed. Therefore, as in Embodiment 1, AlPd is generated by adding palladium to the gold wire used as the wire 27. That is, by chemically bonding aluminum, which is the material of the bonding pad 25, with palladium, the ratio of aluminum to gold, which is the material of the wire 27, can be reduced, so that many alloy layers with high bonding strength are generated. It becomes easy. Thereby, the adhesive force of the wire 27 and the bonding pad 25 can be improved.

  Subsequently, after the wire bonding process is completed, as shown in FIG. 18, the metal chips 33a and 33b are sandwiched from above and below the lead frame on which the semiconductor chip 24 is mounted. At this time, a cavity is formed in the resin sealing region. And resin is inject | poured from the gate currently formed in metal mold | die 33a, 33b, and the semiconductor chip 24 is resin-sealed. FIG. 19 is a cross-sectional view showing a state where the semiconductor chip 24 is sealed with a resin 34. As shown in FIG. 19, the semiconductor chip 24, the wire 27, the tab 20, and a part of the lead 21 (inner lead) are sealed with a resin 34. The resin 34 is processed into a substantially rectangular parallelepiped shape, and a part of the lead 21 (outer lead) protrudes from the side surface of the substantially rectangular parallelepiped.

  Next, the lead (outer lead) 21 exposed from the resin 34 is cut, and the resin-sealed semiconductor device is singulated. Then, as shown in FIG. 20, the outer lead, which is a part of the lead 21, is formed into an L shape, and the semiconductor device is completed. In this manner, a semiconductor device having a QFP package form can be manufactured.

  Thereafter, burn-in testing is performed on the completed semiconductor device, and a final appearance inspection is performed. Then, the semiconductor device determined to be non-defective by inspection is shipped after being packed. The shipped semiconductor device is mounted on a mounting board, for example, at the shipping destination. FIG. 21 is a cross-sectional view showing a state where the completed semiconductor device is mounted on the mounting substrate 35. As shown in FIG. 21, a terminal 36 is provided on the mounting substrate 35, and the semiconductor device is mounted on the mounting substrate 35 by connecting the lead 21 of the semiconductor device to the terminal 36 via a solder 37. And a semiconductor product can be formed.

  Here, lead-containing solder (Sn—Pb-based) is used for solder joints, and has many advantages of excellent workability because the joint has high reliability and low melting point. ing. For this reason, solder containing lead is often used for assembling electrical and electronic equipment. However, electrical and electronic products are increasingly discarded due to the end of their useful lives and the appearance of new products. And since this waste is nonflammable, it is currently left as it is or crushed and buried in the ground. For this reason, lead-containing solder used in discarded electrical and electronic equipment is eluted and mixed into groundwater or flows into rivers. Then, some form of lead is taken up by humans and its toxicity is regarded as a problem.

  In recent years, environmental problems have been highlighted all over the world, and there is a movement to regulate toxic lead contained in solder. For this reason, solder that does not contain lead is used instead of solder that contains lead. Examples of the solder not containing lead include an alloy of tin, silver and copper, an alloy of tin and copper, and an alloy of tin and silver. By using these lead-free solders for bonding at the time of mounting, an environmentally friendly semiconductor product can be manufactured.

(Embodiment 2)
In the first embodiment, as an example in which the wire bonding process is performed in a state where one end portion of the lead is inclined, an example using a lead frame having a structure in which one end portion is inclined has been described. In the second embodiment, an example will be described in which the heat stage on which the lead frame is arranged is inclined, and the lead frame is pressed against the heat stage to perform wire bonding in a state where one end portion of the lead is inclined.

  Until wire bonding is performed, the same steps as those in the first embodiment are performed, and thus the description thereof is omitted. However, in the second embodiment, unlike the first embodiment, the tip of the lead constituting the lead frame is not inclined. That is, in the second embodiment, a normal lead having no inclination is used.

  FIG. 22 is a top view showing how the wire bonding step in the second embodiment is performed. As shown in FIG. 22, a lead frame having leads 41 and tabs 40 is disposed on the heat stage 43, and a semiconductor chip 42 is mounted on the tabs 40. In the first embodiment, an example in which a large tab having a size larger than that of the semiconductor chip is used has been described. However, as shown in the second embodiment, a tab (small tab) having a size smaller than that of the semiconductor chip 42 is used. 40 may be used.

  The lead frame on which the semiconductor chip 42 is mounted is pressed from above by the pressing piece 44, and wire bonding is performed in this state. 23 is a cross-sectional view showing a cross section taken along line AA of FIG. As shown in FIG. 23, a lead frame including tabs 40 and leads 41 is arranged on the heat stage 43. The tab 40 is disposed so as to be embedded in the heat stage 43, and the semiconductor chip 42 mounted on the tab 40 is in direct contact with the heat stage 43. Therefore, the heat generated in the heat stage 43 is efficiently conducted to the semiconductor chip 42. For this reason, since the bonding pad 45 formed on the semiconductor chip 42 can be sufficiently heated, the ball 46 can be pressed onto the bonding pad 45 satisfactorily.

  The area where the lead 41 of the heat stage 43 is placed is provided with an inclination. That is, the heat stage 43 is inclined so that the tip portion of the lead 41 is inclined downward. On the lead 41, a presser piece 44 that presses the lead 41 is disposed, and a tip end of the lead 41 is pressed against the heat stage 43 by a presser claw 48 protruding downward from the presser piece 44. As a result, the tip of the lead 41 is inclined according to the shape of the heat stage 43. At this time, in order to suppress the tip portion of the lead 41 from being vibrated by the ultrasonic wave applied to the ball 46, it is necessary to press the vicinity of the tip portion of the lead 41 with the presser claw 48 as much as possible. However, since the tip portion of the lead 41 is silver-plated, in order to prevent the silver clad from adhering to the presser claws 48 and contaminating it, at least the region outside the silver-plated region can be pressed. is necessary. From the above, in the present second embodiment, the presser claw 48 is positioned outside the silver plating region formed at the tip of the lead 41 and in a portion inclined in the heat stage 43. Is preferred.

  As described above, in the second embodiment, the tip of the lead 41 is inclined by forcibly pressing the normal lead 41 that is not inclined against the heat stage 43 having an inclined shape. In this state, wire bonding is performed using the capillary 49.

  First, a bonding pad 45 formed on the semiconductor chip 42 and a ball 46 made of, for example, a gold wire are pressure-bonded using a capillary 49 (primary bonding). At this time, the tip of the capillary 49 has an angle, but the size is, for example, about 3 degrees to 15 degrees. For this reason, the load applied to the ball 46 and the ultrasonic wave can be sufficiently prevented from escaping to the outside of the ball, so that an alloy layer is formed at the boundary between the bonding pad 45 and the ball 46 to ensure sufficient adhesive strength. be able to.

  Subsequently, the capillary 49 is moved to connect the wire 47 and the lead 41 (secondary bonding). At this time, a sufficient thickness cannot be ensured only by the angle formed at the tip of the capillary 49. That is, it is impossible to increase the thickness at the crimping portion between the wire 47 and the lead 41. However, in the second embodiment, since the bonding is performed with the tip of the lead 41 inclined downward, the thickness at the crimped portion between the wire 47 and the lead 41 can be increased.

  FIG. 24 is an enlarged view of the crimping portion between the wire 47 and the lead 41. As shown in FIG. 24, the heat stage 43 is inclined, and the inclination angle is an angle β. Since the lead 41 is pressed against the heat stage 43 inclined at this angle β, the inclination of the angle β is formed at the tip of the lead 41. Therefore, the angle between the capillary 49 and the lead 41, in other words, the angle between the wire 47 and the lead 41 is determined by the inclination of the lead 41 and the angle α formed at the tip of the capillary 49. The resulting angle β is an angle γ. That is, the angle when the wire 47 and the lead 41 are crimped is larger than the angle α formed at the tip of the capillary 49. Thereby, since the angle between the wire 47 and the lead 41 can be increased, it is possible to sufficiently increase the thickness at the crimping portion of the wire 47 and the lead 41. That is, a sufficient thickness can be obtained without increasing the angle of the tip of the capillary 49. For this reason, it is possible to improve the connection reliability between the wire 47 and the lead 41 in the secondary bonding while ensuring the connection reliability between the bonding pad 45 and the ball 46 in the primary bonding.

  As described above, according to the second embodiment, the angle between the lead 41 and the wire 47 at the time of crimping can be increased without providing the tip of the lead 41 with an inclination by, for example, pressing. That is, by providing the heat stage 43 with an inclination and pressing the lead 41 against the heat stage 43, the tip of the lead 41 can be inclined. As described above, according to the second embodiment, the present invention can be applied to a normal lead frame in which no inclination is formed. Therefore, the strength of the lead 41 is not reduced compared to the first embodiment in which the tip portion of the lead 41 is processed.

  However, when the means as in the second embodiment is applied, the tip of the lead 41 does not return to the original position even after the presser claw 48 is released due to the load of the presser claw 48, and is bent downward. There is a possibility that it will be in the state. In the case of the QFP package as in the second embodiment, since the lower side of the lead 41 is also covered with the resin, there is no problem even if the shape of the lead 41 is bent downward. 3 is applied to a QFN package in which a part of the lead described in FIG. 3 is exposed from the bottom surface of the resin, the leading end of the lead protrudes greatly from the bottom surface of the resin, and such a semiconductor device is mounted on the mounting substrate. In some cases, this protruding portion may become an obstacle.

  Note that the angle β provided to the heat stage 43 is desirably 3 degrees or more and 15 degrees or less for the same reason as described in the first embodiment.

(Embodiment 3)
In the first embodiment, the semiconductor device whose package form is QFP has been described as an example. However, in the third embodiment, the present invention is applied to a semiconductor device whose package form is QFN (Quad Flat Non-Leaded package). An example will be described.

  One type of package in which a semiconductor chip mounted on a lead frame is sealed with a sealing body made of resin is QFN.

  FIG. 25 is a perspective view showing the external appearance of a semiconductor device 50 whose package form is QFN. As shown in FIG. 25, the semiconductor device 50 is covered with a substantially rectangular parallelepiped resin 51, and the ends of the leads 52 are exposed on the side surfaces of the substantially rectangular parallelepiped formed of the resin 51.

  FIG. 26 is a plan view of the semiconductor device 50 viewed from the back side. As shown in FIG. 26, a terminal 53 exposed from the resin 51 is formed on the back surface of the semiconductor device 50. The terminal 53 is a part of the lead 52 and is used for connection to a mounting board.

  27 is a cross-sectional view showing a cross section taken along line AA of FIG. As shown in FIG. 27, a tab 54 is formed at the center of the semiconductor device 50, and a lead 52 is formed around the tab 54. A terminal 53 protruding slightly is formed at the bottom of the lead 52. A semiconductor chip 55 is mounted on the tab 54, and a bonding pad 56 and a lead 52 formed on the upper surface of the semiconductor chip 55 are electrically connected using a ball 57 and a wire 58. The semiconductor chip 55, the lead 52, the ball 57, the wire 58 and the like are sealed with the resin 51, and the terminal 53 is exposed on the bottom surface of the resin 51.

  The QFN configured as described above has an advantage that the mounting area is reduced as compared with the QFP that configures the terminal by extending the lead laterally from the side surface of the resin.

  Here, also in the third embodiment, as in the first embodiment, an inclination is provided at one tip portion of the lead (tip portion nearer to the tab 54). Thereby, as described in the first embodiment, the connection reliability between the wire 58 and the lead 52 can be improved.

  Next, a method for manufacturing a semiconductor device according to the third embodiment will be described. First, as shown in FIG. 28, a lead frame having tabs 61 and leads 62 is prepared. In this lead frame, an inclination is provided at one end of the lead 62 (the end close to the tab 61). This inclination can be formed by pressing, for example. For the same reason as in the first embodiment, it is desirable that the angle of inclination is, for example, 3 degrees or more and 15 degrees or less. A silver plating 63 is formed at one end of the inclined lead 62. Further, a slightly projecting terminal 62 a is formed on the back surface of the lead 62. The lead frame configured as described above is arranged on the stage 60. At this time, the terminal 62 a formed on the back surface of the lead 62 is disposed so as to be accommodated in a groove provided in the stage 60.

  Next, the semiconductor chip 64 is mounted on the tab 61 arranged on the stage 60. The tab 61 and the semiconductor chip 64 are bonded using, for example, an adhesive. A bonding pad 65 is formed on the upper surface of the semiconductor chip 64.

  Subsequently, as shown in FIG. 29, the bonding pad 65 formed on the semiconductor chip 64 and the lead 62 are electrically connected using a ball 68 and a wire 69 while the lead frame is held by the holding jig 66. That is, the bonding pad 65 and the ball 68 are connected using the capillary 67 (primary bonding), and then the capillary 67 is moved to connect the wire 69 and the lead 62 (secondary bonding). This wire bonding step is performed, for example, in the same manner as in the first embodiment shown in FIGS.

  Specifically, the ball 68 is pressure-bonded to the bonding pad 65 using the capillary 67. At this time, since the angle formed at the tip of the capillary 67 is small, the load and ultrasonic waves applied to the ball 68 do not escape to the outside of the ball 68. Therefore, connection reliability between the ball 68 and the bonding pad 65 can be ensured.

  Subsequently, the capillary 67 is moved to crimp the wire 69 and the lead 62. At this time, since the tip of the lead 62 is inclined, the angle formed between the wire 69 and the lead 62 is equal to the angle provided at the tip of the capillary 67. It is the sum of the angles at which the tip is inclined. Therefore, the wire 69 and the lead 62 are crimped at an angle larger than the angle provided at the tip of the capillary 67. For this reason, the thickness of the crimping part of the wire 69 and the lead 62 can be increased, and the connection reliability between the wire 69 and the lead 62 can be improved. That is, also in the third embodiment, as in the first embodiment, the wire 69 and the lead 62 are secured while ensuring the connection reliability between the bonding pad 65 and the ball 68 even if the diameter of the wire 69 is reduced. Connection reliability can be improved.

  Next, the lead frame is mounted on the molds 70 and 72 shown in FIG. FIG. 30 is a cross-sectional view showing a part of the molds 70 and 72 (area corresponding to about one QFN). When the semiconductor chip 64 is resin-sealed using the molds 70 and 72, first, a thin resin sheet 71 is laid on the surface of the mold 70, and a lead frame is disposed on the resin sheet 71. The lead frame is placed with the surface on which the terminal 62a is formed facing downward, and the terminal 62a and the resin sheet 71 are brought into contact with each other. In this state, the resin sheet 71 and the lead frame are sandwiched between the mold 70 and the mold 72. In this way, the terminal 62 a located on the lower surface of the lead 62 presses the resin sheet 71 by the pressing force of the mold 72, so that the tip portion of the terminal 62 a bites into the resin sheet 71.

  As a result, after the molten resin is injected into the gap between the mold 70 and the mold 72 to mold the resin, the mold 70 and the mold 72 are separated, as shown in FIG. The leading end portion of the terminal 62 a that has bited in protrudes outward from the back surface of the resin 73.

  Then, after printing a solder layer on the surface of the terminal 62a exposed on the back surface of the resin 73, and subsequently forming a mark such as a product name on the surface of the resin 73, the lead frame is cut using a dicer. The semiconductor device shown in FIG. In this manner, a semiconductor device having a package form of QFN can be manufactured. Thereafter, burn-in testing is performed on the completed semiconductor device, and a final appearance inspection is performed. Then, the semiconductor device determined to be non-defective by inspection is shipped after being packed. The shipped semiconductor device is mounted on a mounting board, for example, at the shipping destination. FIG. 33 is a cross-sectional view showing a state where the completed semiconductor device is mounted on the mounting substrate 74. As shown in FIG. 33, a terminal 75 is provided on the mounting board 74, and the semiconductor device is mounted on the mounting board 74 by connecting the terminal 62 a of the semiconductor device to the terminal 75 via the solder 76. And a semiconductor product can be formed. Here, for example, by using so-called lead-free solder which does not contain lead as the solder 76, a semiconductor product in consideration of the environment can be manufactured.

  In the third embodiment, the tip of the lead 62 is configured to be inclined. However, as described in the second embodiment, the tip of the lead 62 is not inclined and the lead frame is mounted. The stage to be placed may be inclined. Then, wire bonding may be performed by pressing the lead frame against the inclined stage so that one end of the lead 62 is inclined. However, when the package form is QFN, the terminal 62a protrudes from the back surface of the lead 62 and is exposed. If the lead 62 is pressed against the inclined stage, the lead 62 may remain bent thereafter. Then, the portion of the terminal 62a protrudes more than necessary, and the height with the other terminal 62a does not match, and there is a possibility that a connection failure occurs in some of the terminals 62a during mounting. Therefore, in the case of QFN, as compared with the method of wire bonding in a state where one end portion of the lead is inclined by pressing the lead frame against the inclined stage, the one end of the lead 62 as in the third embodiment. It is desirable to employ a method of wire bonding in a state in which the part itself is processed and provided with an inclination.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

  The present invention can be widely used in the manufacturing industry for manufacturing semiconductor devices.

It is a figure which shows a capillary. It is sectional drawing which shows the front-end | tip part of a capillary. It is sectional drawing which shows a mode that the load applied to the ball | bowl escapes outside. It is a perspective view which shows QFP in Embodiment 1 of this invention. It is sectional drawing which shows the cross section cut | disconnected by the AA line of FIG. It is a top view which shows the internal structure of QFP. 7 is a cross-sectional view showing a manufacturing step of the semiconductor device in the first embodiment. FIG. FIG. 8 is a cross-sectional view showing a manufacturing step of the semiconductor device following that of FIG. 7; FIG. 9 is a cross-sectional view showing a manufacturing step of the semiconductor device following that of FIG. 8; It is a perspective view which shows one process of wire bonding. FIG. 11 is a perspective view showing a step of wire bonding following FIG. 10. It is sectional drawing which shows a mode that the load was applied to the ball | bowl. FIG. 12 is a perspective view showing a step of wire bonding following FIG. 11. FIG. 14 is a perspective view showing a step of wire bonding subsequent to FIG. 13. It is sectional drawing which shows the crimping | compression-bonding part of a wire and a lead. FIG. 15 is a perspective view showing a step of wire bonding subsequent to FIG. 14. FIG. 17 is a perspective view illustrating a step of wire bonding following FIG. 16. 7 is a cross-sectional view showing a manufacturing step of the semiconductor device in the first embodiment. FIG. FIG. 19 is a cross-sectional view showing the manufacturing process of the semiconductor device, following FIG. 18; 1 is a side view showing a semiconductor device in a first embodiment. 3 is a diagram illustrating a state in which the semiconductor device according to the first embodiment is mounted on a mounting substrate. FIG. FIG. 10 is a top view showing a state of performing a wire bonding step in the second embodiment. It is sectional drawing which shows the cross section cut | disconnected by the AA line of FIG. It is sectional drawing which shows the crimping | compression-bonding part of a wire and a lead. FIG. 10 is a perspective view showing a QFN in a third embodiment. It is the top view which looked at QFN in Embodiment 3 from the back. It is sectional drawing which shows the cross section cut | disconnected by the AA line of FIG. FIG. 11 is a cross-sectional view showing a manufacturing step of the semiconductor device in the third embodiment. FIG. 29 is a cross-sectional view showing the manufacturing process of the semiconductor device, following FIG. 28; FIG. 30 is a cross-sectional view showing a manufacturing step of the semiconductor device following that of FIG. 29; FIG. 31 is a cross-sectional view showing a manufacturing step of the semiconductor device following that of FIG. 30; FIG. 10 is a side view showing a semiconductor device in a third embodiment. FIG. 10 is a diagram illustrating a state where the semiconductor device according to the third embodiment is mounted on a mounting substrate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Capillary 1a Tip part 2 Bonding pad 3 Ball 10 Semiconductor device 11 Resin 12 Outer lead 13 Inner lead 13a Tip part 14 Tab 15 Semiconductor chip 16 Bonding pad 17 Ball 18 Wire 20 Tab 21 Lead 21a Tip part 22 Silver plating 23 Stage 24 Semiconductor Chip 25 Bonding pad 26 Ball 27 Wire 28 Holding jig 29 Capillary 30 Ultrasonic horn 31 Gold wire 32 Discharge torch 33a Mold 33b Mold 33b Mold 34 Resin 35 Mounting substrate 36 Terminal 37 Solder 40 Tab 41 Lead 42 Semiconductor chip 43 Heat stage 44 Presser piece 45 Bonding pad 46 Ball 47 Wire 48 Presser claw 49 Capillary 50 Semiconductor device 51 Resin 52 Lead 53 Terminal 54 Tab 55 Half Body chip 56 Bonding pad 57 Ball 58 Wire 60 Stage 61 Tab 62 Lead 62a Terminal 63 Silver plating 64 Semiconductor chip 65 Bonding pad 66 Holding jig 67 Capillary 68 Ball 69 Wire 70 Mold 71 Resin sheet 72 Mold 73 Resin 74 Mounting substrate 75 terminals 76 solder

Claims (20)

(A) a step of wire bonding the bonding pad on the semiconductor chip and one end of the lead using a capillary whose tip is tapered;
The method (a) is performed in a state where one end portion of the lead is inclined.   2. The method of manufacturing a semiconductor device according to claim 1, wherein one end portion of the lead is inclined so as to become thinner toward the tip end.   2. The method of manufacturing a semiconductor device according to claim 1, wherein one end of the lead is processed to be inclined.   4. The method of manufacturing a semiconductor device according to claim 3, wherein one end portion of the lead is formed to be inclined by press working.   4. The method of manufacturing a semiconductor device according to claim 3, wherein one end portion of the lead is inclined at an angle of 3 degrees to 15 degrees.   2. The semiconductor device according to claim 1, wherein in the step (a), wire bonding is performed in a state where the one end portion of the lead is inclined by pressing the one end portion of the lead against an inclined stage. 3. Production method.   The method of manufacturing a semiconductor device according to claim 6, wherein the stage is inclined at an angle of 3 degrees to 15 degrees.   The method of manufacturing a semiconductor device according to claim 1, wherein at least one region of the lead connected to the wire is inclined.   2. The method of manufacturing a semiconductor device according to claim 1, wherein at least one region of the lead that is silver-plated is inclined.   2. The method of manufacturing a semiconductor device according to claim 1, wherein at least a region from the tip of one tip of the lead to 500 [mu] m is inclined. further,
(B) a step of sealing the semiconductor chip and the lead with a resin,
2. The method of manufacturing a semiconductor device according to claim 1, wherein the other end of the lead protrudes from a side surface of the resin. further,
(B) a step of sealing the semiconductor chip and the lead with a resin,
2. The method of manufacturing a semiconductor device according to claim 1, wherein the lead has a portion exposed from a bottom surface of the resin.   2. The method of manufacturing a semiconductor device according to claim 1, wherein the wire connecting the bonding pad and the lead is a gold wire.   The method of manufacturing a semiconductor device according to claim 1, wherein a wire connecting the bonding pad and the lead is formed of gold added with palladium.   12. The method of manufacturing a semiconductor device according to claim 11, wherein the other end portion of the lead and the mounting substrate are connected by solder not containing lead.   13. The method of manufacturing a semiconductor device according to claim 12, wherein a portion of the lead exposed from the bottom surface of the resin is connected to the mounting substrate with solder containing no lead.   2. The method of manufacturing a semiconductor device according to claim 1, wherein an inclination of 3 degrees to 15 degrees is formed at a tip of the capillary. (A) a semiconductor chip;
(B) leads arranged around the semiconductor chip;
(C) a wire for electrically connecting the semiconductor chip and one end of the lead;
(D) comprising a resin for sealing the semiconductor chip, the lead and the wire;
One end of the lead to which the wire is connected is inclined.   The semiconductor device according to claim 18, wherein the slope provided at one end of the lead is formed by pressing the lead.   19. The semiconductor device according to claim 18, wherein the inclination provided at one end portion of the lead is an angle of 3 degrees to 15 degrees.

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