MX2012009680A - Printed wiring board. - Google Patents

Abstract

A printed wiring board in which a surface mount device is mounted on an insulating base material using reflow type soldering that uses solder paste, includes a first surface on which the surface mount device is mounted; and a second surface on an opposite side to the first surface, wherein a venting hole penetrating from the first surface to the second surface is formed, and the venting hole is formed directly below the surface mount device.

Description

PRINTED CIRCUIT PANEL FIELD OF THE INVENTION The present invention relates to a printed circuit board.

Priority is claimed over Japanese Patent Application No. 201 1-183323, filed on August 25, 2011, the content of which is incorporated herein by reference.

RELATED TECHNIQUE In recent years, a large number of surface mount devices (SMDs = Surface Mount Devices) have been mounted on a printed circuit board. Said surface mounting device is placed on a printed circuit board with solder paste containing, for example, powder welder and interposed flux. Thereafter, the surface mount device is attached to the printed circuit board using a reflow-type weld when melting the solder paste by heating.

Reflow type welding is carried out by melting the solder paste in a uniform temperature environment which is equal to or less than the heat treatment temperature of the surface mount device or the like. However, if the surface mount device is a device having large thermal capacity, such as a large electrolytic capacitor, a quantity of heat is lost in the surface mount device, and as a result, the thermal efficiency of the Welding paste is reduced. That is, depending on the position of the arrangement, variation in the temperature of the solder paste occurs, so that there is a concern that partially fused solder paste can be generated.

In order to avoid the generation of said non-melted solder paste, Consider taking a countermeasure to increase the heating temperature of the solder paste. However, in a case where the heating temperature exceeds the heat treatment temperature of the surface mounting device or the like, said countermeasure can not be used. Therefore, in Patent Document 1, a printed circuit panel having a penetration through a hole leading to a surface is proposed. In said printed circuit board, hot air is supplied from the opposite side to a front surface on which a surface mount device is mounted, and the surface is heated locally by the hot air passing through the penetration through the hole . Therefore, it creates a method to suppress the generation of non-molten solder paste.

REFERENCE DOCUMENT PATENT DOCUMENT [Patent Document 1] Unexamined Japanese Patent Application, First Publication No. 10-229273 COMPENDIUM OF THE INVENTION PROBLEMS TO BE RESOLVED BY THE INVENTION However, in the printed circuit panel described in Patent Document 1, the hot air supplied from the opposite side to the front surface on which the surface mount device is mounted and passes through the penetration through the hole, it flows beyond without remaining in the proximity of the surface. For this reason, in the printed circuit panel described in Patent Document 1, it is not possible to sufficiently raise the temperature of the solder paste, so it is not possible to reliably avoid the solder paste without melting.

The present invention has been developed in view of the problem described above and has the purpose of avoiding the generation of solder paste without melting when a surface mount device is attached to a printed circuit board using reflow type welding, and therefore reliably joining the surface mount device and the printed circuit board together.

METHODS TO SOLVE THE PROBLEM To solve the problem described above, one aspect of the invention has the following configurations. (1) According to one aspect of the invention, a printed circuit board is provided in which a surface mount device is mounted on an insulating base material using reflow type welding using solder paste, the circuit board Printed includes: a first surface on which the surface mount device is mounted; and a second surface on a side opposite the first surface, wherein a ventilation hole penetrating from the first surface to the second surface is formed, and the ventilation hole is formed directly below the surface mounting device. (2) On the printed circuit board according to (1) above, the surface mount device may be a high thermal capacity surface mount device having thermal capacity exceeding a predetermined threshold value or a mounting device surface of low thermal capacity having a thermal capacity equal to or less than the threshold value, and the ventilation hole can only be formed directly below the high thermal capacity surface mount device. (3) On the printed circuit board according to the above (2), a thermal conduction prevention member can be placed between the low thermal capacity surface mounting device and the ventilation hole. (4) The printed circuit board according to any of (1) to (3) above may further include: an electrically conductive layer that covers an inner wall surface of the ventilation hole, wherein the electrically conductive layer can be connected to a terminal on which the solder paste is placed. (5) On the printed circuit board according to any one of (1) to (4) above, a plurality of ventilation holes may be formed and a pattern of arrangement of the ventilation holes may correspond to a layout pattern of a plurality of connection terminals of a dual in-line package part (DIP = Dual In-line Package). (6) On the printed circuit board according to (1) above, a diameter of the ventilation hole may become smaller as it advances towards the second surface from the first surface. (7) On the printed circuit board according to (1) above, a diameter of the ventilation hole may become larger as it advances toward the second surface from the first surface.

EFFECTS OF THE INVENTION In accordance with the printed circuit panel described in (1) to (7) above, the vent hole that allows gas to pass from the side of the second surface onto the opposite side of the first surface on which the device Surface mounting is mounted, next to the first surface, is provided and the ventilation hole is formed directly under the surface mounting device. For this reason, in reflow type welding, hot air which has passed through the ventilation hole from the side of the second surface to the side of the first surface is blown to the surface mounting device. Because the hot air that is blown to the surface mount device in this manner, even in a case where the thermal capacity of the surface mount device is large, the temperature of the surface mount device rises to the same temperature as the temperature environment in a short time. For this reason, it is possible to avoid a decrease in the heating efficiency of the solder paste because a quantity of heat is lost to the surface mounting device.

Still further, as described above, the hot air that has passed through the vent hole is blown to the surface mount device. Then, the hot air remains between the surface mount device and the printed circuit board, so that it is possible to ensure a longer heat exchange time between the hot air and the solder paste, so that it is possible to heat more efficiently the solder paste In this way, in a case of mounting the surface mount device using reflow-type welding, it becomes possible to efficiently heat the solder paste. For this reason, the generation of non-molten solder paste is avoided, so that it is possible to reliably join the surface mount device and the printed circuit board together.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1A is a plan view of a schematic configuration diagram of a printed circuit board in relation to a first embodiment of the invention.

Figure 1B is an enlarged schematic view including an electrolytic capacitor of the schematic configuration diagram of the printed circuit board in relation to the first embodiment of the invention.

Figure 1C is a vertical cross-sectional view taken along line A-A of Figure 1B.

Figure 2A is a schematic diagram showing the first assembly process of the electrolytic capacitor on the printed circuit board in relation to the first embodiment of the invention.

Figure 2B is a schematic diagram showing the second process of mounting the electrolytic capacitor on the printed circuit board in relation to the first embodiment of the invention.

Figure 3 is a diagram schematically showing a configuration of a printed circuit board in relation to a second embodiment of the invention and is a partially enlarged cross-sectional view including an electrolytic capacitor.

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, the embodiments of a printed circuit panel according to the invention will be described based on the drawings.

Additionally, in the following drawings, to show each member in a recognizable size, the scale of each member has been appropriately changed.

(First Mode) As shown in Figure 1A, a printed circuit panel 1 related to this embodiment is a substrate on which a large number of electronic parts including an electrolytic capacitor of surface mount type 100 (a surface mount device) is mounted.

In Figure 1A, some of the assembled parts are shown and a circuit pattern or the like of the printed circuit board 1 is omitted. As shown in Figure 1 C, the printed circuit panel 1 that relates to this embodiment includes an insulating base material 2, circuit patterns 3, and ventilation holes 4.

In the following description, the upper surface (a first surface) of the printed circuit panel 1 in Figure 1 C will be referred to as a front surface 1 a and the lower surface (a second surface) of the printed circuit panel 1 in Figure 1C it will be referred to as a back surface 1b.

The insulating base material 2 is a plate-shaped member made of an insulating material such as a glass epoxy material or a glass composite material and is provided with through hole or the like to connect the internal layer patterns to each other in addition to the ventilation hole 4.

The circuit pattern 3 is an electrically conducting layer made of copper. In this embodiment, a pattern of the front surface 3a that is formed on the front surface 1 a of the printed circuit board 1, a pattern of the rear surface 3b that is formed on the rear surface 1 b of the printed circuit board 1, and internal layer patterns 3c and 3d that are formed in the insulating base material 2 are the circuit patterns 3.

The inner layer pattern 3c and the internal layer pattern 3d are formed in different layers in a predetermined range in the thickness direction of the insulating base material 2.

The front surface pattern 3a, the rear surface pattern 3b, and the inner layer patterns 3c and 3d are connected to each other by copper cladding layers (not shown) formed on the inner wall surfaces of the provided traversing holes in predetermined places.

In the front surface pattern 3a, a terminal 3a 1 is provided to which a first terminal 101 is joined by welding H1 and a terminal 3a2 to which a second terminal 102 of the electrolytic capacitor 100 is joined by welding H2. The terminals 3a 1 and 3a2 are also places where the solder paste P (Figure 2B) is placed when the electrolytic capacitor 100 is welded in a reflow manner.

Additionally, the internal layer patterns 3c and 3d on the printed circuit panel 1 related to this embodiment are provided to avoid locations directly under the terminals 3a1 and 3a2, as shown in Figure 1C. For this reason, only the insulating base material 2 having low thermal conductivity is present below terminals 3a 1 and 3a2.

The vent hole 4 is a penetrating hole penetrating from the front surface 1 a of the printed circuit board 1 to the rear surface 1 b and two ventilation holes (a vent hole 4 a and a vent hole 4 b) are provided directly under the 100 electrolytic capacitor.

Due to the vent hole 4, gas can pass from the rear surface side 1 b of the printed circuit board 1 to the side of the front surface 1 a (or vice versa).

An area directly below the electrolytic capacitor 100 represents an area covered by the electrolytic capacitor 100 of the printed circuit board 1 (an area that is superimposed on the electrolytic capacitor 100 when viewed from the side of the front surface 1a).

Although they will be described later, the ventilation holes 4 cause the hot air W that is blown from the side of the back surface 1 b to flow to the side of the front surface in the case of surface mounting of the electrolytic capacitor 100 on the panel of printed circuit 1 using a reflow type weld.

Arranged positions of the ventilation holes 4 are optional, provided that they are placed directly below the electrolytic capacitor 100. However, it is preferable to form the ventilation holes 4 at positions where the heat transfer to the solder paste P (Figure 2B) which is used at the time of welding the electrolytic capacitor 100 is carried out efficiently.

Specifically, the ventilation holes 4 are placed as close as possible to the terminals 3a 1 and 3a2 where the solder paste P is placed.

Alternately, the ventilation holes 4 are placed in positions where the hot air W, the direction of flow which is changed by passing through ventilation holes 4 and then colliding with the electrolytic capacitor 100, is blown to the terminals 3a 1 and 3a2.

As shown in Figure 1 C, the inner wall surface of the ventilation hole 4 is covered by copper foil 5 (an electrically conductive layer).

The copper foil 5 is formed by, for example, galvanizing and connecting to terminals 3a 1 and 3a2, as shown in Figure 1B.

The copper foil 5a covering the inner wall surface of the ventilation hole 4a is connected to the termination 3a 1 and the copper foil 5b covering the inner wall surface of the ventilation hole 4b is connected to the terminal 3a2.

Although not shown in Figure 1, the copper sheets 5a and 5b are connected to the rear surface pattern 3b on the rear surface 1b of the printed circuit panel 1 and electrically connected to the front surface pattern 3a and the pattern of rear surface 3b with each other. For this reason, each of the copper sheets 5a and 5b functions as a circuit portion.

A center point separation distance D between a vent hole 4a (the vent hole 4 is placed on the top side in Figure 1 B) of the two vent holes 4 and the other vent hole 4b (the vent hole 4). Ventilation 4 placed on the lower part in Figure 1 B) is configured to be equal to the separation distance of the center point between the connecting terminals of a DIP part (eg, a capacitor, a diode, or the like) that is commonly used.

That is, a disposition pattern of the two (plurality of) ventilation holes 4 corresponds to a connection terminal arrangement pattern of a given DIP part.

The copper sheets 5a and 5b that function as a circuit are provided on the inner wall surfaces of the ventilation holes 4. For this reason, in a case where the printed circuit panel 1 related to this embodiment is used for other purposes , it is also possible to mount a DIP part using the ventilation holes 4.

As shown in Figure 1C, in the printed circuit panel 1 related to this embodiment, in a case of carrying out welding of the electrolytic capacitor 100, an electronic part is not placed near the ventilation holes 4 on the side of the electrode. the rear surface 1 b so that the hot air W flows smoothly into the ventilation holes 4.

Additionally, as shown in Figure 1A, three electrolytic capacitors 100 were installed on the printed circuit panel 1 related to this embodiment, and the ventilation holes 4 were provided directly below each electrolytic capacitor 100.

Next, a welding method for mounting the electrolytic capacitor 100 on the printed circuit panel 1 related to this mode will be described with reference to Figures 2A and 2B. In the following description, a process for welding the electrolytic capacitor 100 to the printed circuit board 1 is described. However, in fact, other electronic parts are also attached simultaneously to the printed circuit board 1 in a welding process which is described below.

In this embodiment, the electrolytic capacitor 100 is attached to the printed circuit board 1 using a reflow type weld. First, as shown in Figure 2A, the solder paste P containing solder powder and flux is positioned with respect to the terminals 3a 1 and the terminal 3a2.

The solder paste P is placed on the terminal 3a 1 and the terminal 3a2 by, for example, a well-known printing technique or the like.

Subsequently, as shown in Figure 2B, the electrolytic capacitor 100 is positioned such that the first terminal 101 comes into contact with the solder paste P1 placed on the terminal 3a1 and the second terminal 102 comes into contact with the solder paste. welding P2 placed on terminal 3a2.

Subsequently, as shown in Figure 2B, hot air W is supplied to the printed circuit board 1 from each side of the front surface 1 a and the rear surface side 1 b of the printed circuit board 1.

The temperature of the hot air W is set to be below the heat treatment temperature of the electrolytic capacitor 100 and higher than the melting temperature of the solder paste P. For this reason, the solder paste P is heated and melted by the hot air W. Thereafter, the welds H1 and H2 described above are formed by solidifying the molten solder a when the supply of hot air W is stopped, so that the assembly of the electrolytic capacitor 100 is completed.

Here, on the printed circuit panel 1 related to this embodiment, the ventilation holes 4 are provided directly below the electrolytic capacitor 100. For this reason, some of the hot air W supplied to the printed circuit board 1 from the the rear surface 1 b of the printed circuit board 1 passes through the ventilation holes 4 and is blown to the electrolytic capacitor 100. The hot air W is blown to the electrolytic capacitor 100 in this manner, by means of which in a case where the thermal capacity of the electrolytic capacitor 100 is large, the temperature of the electrolytic capacitor 100 rises to the same temperature as the ambient temperature in a short time. For this reason, it is possible to avoid a decrease in the heating efficiency of the solder paste P because a quantity of heat is lost to the electrolytic capacitor 100.

Additionally, as described above, the hot air W that has passed through the ventilation holes 4 is blown to the electrolytic capacitor 100. For this reason, the hot air W remains between the electrolytic capacitor 100 and the printed circuit board 1 , so that it is possible to ensure a longer heat exchange time between the hot air W and the solder paste, so that it is possible to heat the solder paste P more efficiently.

As described above, according to the printed circuit board 1 related to this embodiment, in the case of mounting the electrolytic capacitor 100 using reflow-type welding, it becomes possible to efficiently heat the solder paste P. For this reason, the generation of non-melted solder paste P is avoided, so that it is possible to reliably bond the electrolytic capacitor 100 and the printed circuit panel 1 together.

In fact, reflow type welding was carried out in the same environment on the printed circuit panel described in Patent Document 1, in which a through hole is formed with respect to a terminal, as in the panel of printed circuit 1 related to this modality. In this case, it was confirmed that in the printed circuit panel 1 related to this mode, the temperature in the vicinity of the solder paste P is higher by temperature in a range of 3 ° C to 5 ° C.

Furthermore, non-melted solder paste P is not only in a state in which the solder paste P which is placed on the terminals 3a1 and 3a2 rarely melts, but also in a state where a little of the solder powder contained in the solder paste P does not melt. Then, it means that a state of electrical or structural fusion previously assumed between the electrolytic capacitor 100 and the printed circuit board 1 is not obtained.

Additionally, in the printed circuit panel 1 related to this embodiment, unlike the printed circuit panel described in Patent Document 1, the holes are not provided with respect to the terminals 3a1 and 3a2. For this reason, it is possible to arrange the solder paste P regardless of the holes, so that it becomes possible to form an optimum cord.

Additionally, in the printed circuit panel described in Patent Document 1, in order to secure a contact area with welding by forming the hole through which it passes with respect to the terminal, it is necessary to make large the external shape of the terminal. In contrast to this, in the printed circuit panel 1 related to this embodiment, since the hole through which it passes is not provided with respect to the terminal, it is not required to make large external forms of terminals 3a1 and 3a2, so that it is possible to make the printed circuit board small 1.

Additionally, in the printed circuit panel 1 related to this embodiment, the copper sheets 5 are provided which are connected to the terminals 3a1 and 3a2 and which also cover the inner wall surfaces of the ventilation holes 4. For this reason, a quantity of heat moves from the copper sheets 5 heated by the hot air W passing through the ventilation holes 4, to the terminals 3a1 and 3a2 by thermal conduction, so that it is possible to heat the terminals 3a more efficiently 1 and 3a2.

Additionally, in the printed circuit panel 1 related to this embodiment, the patterns of the inner layer 3c and 3d are provided to avoid locations directly below the terminals 3a1 and 3a2. For this reason, it is possible to suppress the amount of heat from the hot air W passing through the ventilation holes 4 which is transferred and diffused to the inner layer patterns 3c and 3d, so that it is possible to efficiently heat the terminals 3a1 and 3a2.

(Second Modality) Next, a printed circuit panel 1A related to a second embodiment of the invention will be described. Additionally, in the description of this embodiment, with respect to the same portions as those in the printed circuit panel 1 related to the first embodiment described above, the description is omitted or simplified.

Figure 3 is a diagram schematically showing a configuration of the printed circuit panel 1A related to this embodiment and is a partially enlarged vertical cross-sectional view including the electrolytic capacitor 100. As shown in this drawing, in the printed circuit panel 1A related to this embodiment, a ceramic capacitor 200 (a surface mounting device) is mounted surface on the front surface 1a of the printed circuit board 1A near the electrolytic capacitor 100 in the first embodiment described above . The ceramic capacitor 200 has lower thermal capacity than the electrolytic capacitor 100 and is connected to the terminals 3a3 and 3a4 through the solders H3 and H4.

Said ceramic capacitor 200 is also mounted using a reflow-type weld, similar to the electrolytic capacitor 100. However, since the thermal capacity of the ceramic capacitor 200 is smaller, in one case to carry out reflow-type welding. , the solder paste P placed on the terminals 3a3 and 3a4 melts without being heated by the hot air W that passes through the ventilation holes 4. For this reason, the printed circuit panel 1A related to this mode has no ventilation holes 4 directly below the ceramic capacitor 200.

That is, the printed circuit panel 1A related to this embodiment has the ventilation holes 4 only directly below the electrolytic capacitor 100 having thermal capacity exceeding a predetermined threshold value. The threshold value represents the thermal capacity of the surface mount device, in which it is possible to reliably melt the solder paste P, and it is a value that is determined by an experiment or the like.

Additionally, the printed circuit panel 1A related to this embodiment has an anti-weld 6 (a thermal conduction prevention member) that is placed between the electrolytic capacitor 100 on the front surface 1a and the ceramic capacitor 200.

The anti-weld 6 restricts the wet spreading of the molten solder paste P and also prevents thermal conduction from the terminals 3a1 and 3a2 to the terminals 3a3 and 3a4. In the printed circuit panel 1A related to this embodiment, since the ventilation holes 4 are not provided directly below the ceramic capacitor 200 and the thermal conduction from the terminals 3a 1 and 3a2 to the terminals 3a3 and 3a4 can be avoided, it can be prevent terminals 3a3 and 3a4 from heating unnecessarily.

Preferred embodiments of the invention have been described above with reference to the accompanying drawings. However, it goes without saying that the invention is not limited to the modalities described above. Various forms, combinations, or the like of the respective constituent members shown in the embodiments described above are examples and various changes can be carried out based on the requirements of the design or the like within a range that does not depart from the spirits of the invention.

For example, in a case where a plurality of surface-mounting devices having large thermal capacity are mounted on the printed circuit panel 1 related to the above-described embodiment, it is preferable to provide the ventilation holes 4 directly beneath each device. surface mounting.

Additionally, in the above-described embodiments, a description has been given with respect to a configuration in which a surface mount device having large thermal capacity is the electrolytic capacitor 100. However, the surface mount device may also be another part. electronics such as a microcircuit Cl (Integrated Circuit).

Additionally, in the above-described embodiments, a description has been given regarding a configuration in which two ventilation holes 4 are provided directly below the electrolytic capacitor 100. However, it is also considered to provide three or more ventilation holes or a only ventilation hole directly below electrolytic capacitor 100.

Additionally, in a case where a plurality of ventilation holes 4 are provided directly below the electrolytic capacitor 100, the diameters of all the ventilation holes 4 need not be equal to each other. Additionally, the cross-sectional shape of the vent hole 4 also need not have a circular shape.

In addition, it is also possible to make the diameter of the ventilation hole 4 smaller as it advances towards the front surface 1a from the rear surface 1 b, thus causing the vent hole 4 to have a shape that becomes narrow towards the front surface 1a. In such a case, the ventilation hole 4 easily takes the hot air W from the side of the rear surface 1 b and it is possible to make the flow velocity of the hot air W faster than it is blown from the ventilation hole 4 to the capacitor Electrolytic 100. On the other hand, it is also possible to make the diameter of the larger ventilation hole 4 as it advances towards the front surface 1 a from the rear surface 1 b, thus causing the ventilation hole 4 to have a shape that spreads towards the front surface 1a. In such a case, the amount of hot air W that is introduced into the ventilation hole 4 from the side of the rear surface 1 b is reduced and it is possible to make the slower air flow rate W which is blown from the vent hole 4 to capacitor 100. The shape of vent hole 4 is selected in accordance with the disposed position of the thermistor or the shape of electrolytic capacitor 100 (the surface mount device).

Additionally, in the above-described embodiments, a configuration has been adopted in which the electrically conductive layer covering the surface of the interior wall of the ventilation hole 4 is copper foil 5. It is preferable to use copper when it is considered that it can be formed simultaneously With the circuit pattern and the processing is easy. However, it is also possible to use other electrically conductive layers.

Additionally, in the embodiments described above, a description has been given with respect to a configuration in which the thermal conduction prevention member is the anti-weld or welding mask 6. However, the invention is not limited thereto, and A thermally insulating material that is provided separately can also be used as the thermal conduction prevention member. Furthermore, in a case where a thermal insulation material is provided separately as the thermal conduction prevention member, it is possible to easily form the thermal insulating material in an arbitrary pattern. For this reason, for example, it is possible to form a thermal insulating material in a manner that surrounds a surface mounting device (e.g., electrolytic capacitor 100) having high thermal capacity, or to form a thermal insulating material to encircle a heating device. surface mount (eg, ceramic capacitor 200) that has low thermal capacity.

Industrial Applicability According to the printed circuit panel related to the invention, the generation of non-melted solder paste is avoided, so that it is possible to reliably join a surface mount device and a printed circuit board between

Claims (8)

1. A printed circuit board in which a surface mount device is mounted on an insulating base material using reflow type solder using solder paste, the printed circuit board characterized in that it comprises: a first surface on which the device Surface mount is mounted; and a second surface on an opposite side of the first surface, wherein a ventilation hole penetrating from the first surface to the second surface is formed, and the ventilation hole is formed directly below the surface mounting device.

2. The printed circuit board according to claim 1, characterized in that the surface mounting device is a high thermal capacity surface mounting device having thermal capacity exceeding a predetermined threshold value or a low thermal capacity surface mounting device. which has thermal capacity equal to or less than the threshold value, and the ventilation hole is only formed directly beneath the high-capacity thermal-mounting surface device.

3. The printed circuit board according to claim 2, characterized in that a thermal conduction prevention member is placed between the low thermal capacity surface mounting device and the ventilation hole.

4. The printed circuit board according to any of claims 1 to 3, characterized in that it further comprises: an electrically conductive layer covering an inner wall surface of the ventilation hole, wherein the electrically conductive layer is connected to a terminal on the that the solder paste will be placed.

5. The printed circuit board according to claim 4, characterized in that a plurality of ventilation holes is formed, and a pattern of arrangement of the ventilation holes corresponds to a layout pattern of a plurality of connection terminals of a DIP part.

6. The printed circuit board according to any of claims 1 to 3, characterized in that a plurality of the ventilation holes are formed, and a pattern of arrangement of the ventilation holes corresponds to a layout pattern of a plurality of terminals of connection of a DIP part.

7. The printed circuit board according to any of claims 1 to 3, characterized in that a diameter of the ventilation hole is reduced as it advances towards the second surface from the first surface.

8. The printed circuit board according to any of claims 1 to 3, characterized in that a diameter of the ventilation hole becomes larger as it advances towards the second surface from the first surface.