CA1158970A - Production of electrical laminates - Google Patents
Production of electrical laminatesInfo
- Publication number
- CA1158970A CA1158970A CA000367819A CA367819A CA1158970A CA 1158970 A CA1158970 A CA 1158970A CA 000367819 A CA000367819 A CA 000367819A CA 367819 A CA367819 A CA 367819A CA 1158970 A CA1158970 A CA 1158970A
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- covering sheet
- laminate
- process according
- resin
- rigidity
- Prior art date
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Abstract
Invention: PRODUCTION OF ELECTRICAL LAMINATES
ABSTRACT OF THE DISCLOSURE
A process for producing electrical laminates comprising the steps of impregnating a fibrous substrate with an unsaturated polyester resin which is a liquid at room temperature, laminating a plurality of the resin-impregnated substrates to form a unitary member, sand-wiching the laminate between a pair of convering sheets, and curing the same, the improvement comprising at least one of said pair of covering sheets having a rigidity as defined by the value E?d3kg?cm, wherein E is the flexural modulus in kg/cm2 and d is the thickness in cm, of greater than 3 x 10-3 kg?cm. This results in smooth surface characteristic of the finished laminate after stripping said one of covering sheets.
ABSTRACT OF THE DISCLOSURE
A process for producing electrical laminates comprising the steps of impregnating a fibrous substrate with an unsaturated polyester resin which is a liquid at room temperature, laminating a plurality of the resin-impregnated substrates to form a unitary member, sand-wiching the laminate between a pair of convering sheets, and curing the same, the improvement comprising at least one of said pair of covering sheets having a rigidity as defined by the value E?d3kg?cm, wherein E is the flexural modulus in kg/cm2 and d is the thickness in cm, of greater than 3 x 10-3 kg?cm. This results in smooth surface characteristic of the finished laminate after stripping said one of covering sheets.
Description
7 n This invention relates to a process ~or producing clad or unclad rein~orced polyester resin laminates of elec--trical grade having excellent smooth surface characteristics.
The laminates o~ this type may ~ind uses as insulating plates or printed circuit wiring boards and generally have a thick-ness ~rom O.3 to 5 mm.
Electrical laminates have been conventionally produced by pressing a plurali-ty o~ phenol resin-impregnated paper substrates or epoxy resin-impregnated glass fiber substrates under heating. A prior art process for producing such laminates includes the s-teps o~ impregnating a ~ibrous substrate wlth a ~arnish o~ a solid or crystalline unsaturated polyester resin dissolved in a volati}e ~olvent, evaporating the solvent to ~orm a prepreg, stacking a plurality o~ prepregs and pressing the same under heating. This batch-type process naturally requires large amounts of hand labor and, there~ore, cannot operate at a high productivity.
Unsaturated polyes-ter resins which occur as a liquid at room temperature cannot be used ln this batch process because they do not beoome tack-free Ln the prepreg stage and tend to be ~reely squeezed when the stack of prep.regs is pressed.
How~ever, liquid unsaturated polyester resins have advantages/that the~ do not need any solvent ~or impregnating the substrate and may be cured without generating any bubble ~orming gas and thus without applying substantial pressure.
The laminates o~ this type may ~ind uses as insulating plates or printed circuit wiring boards and generally have a thick-ness ~rom O.3 to 5 mm.
Electrical laminates have been conventionally produced by pressing a plurali-ty o~ phenol resin-impregnated paper substrates or epoxy resin-impregnated glass fiber substrates under heating. A prior art process for producing such laminates includes the s-teps o~ impregnating a ~ibrous substrate wlth a ~arnish o~ a solid or crystalline unsaturated polyester resin dissolved in a volati}e ~olvent, evaporating the solvent to ~orm a prepreg, stacking a plurality o~ prepregs and pressing the same under heating. This batch-type process naturally requires large amounts of hand labor and, there~ore, cannot operate at a high productivity.
Unsaturated polyes-ter resins which occur as a liquid at room temperature cannot be used ln this batch process because they do not beoome tack-free Ln the prepreg stage and tend to be ~reely squeezed when the stack of prep.regs is pressed.
How~ever, liquid unsaturated polyester resins have advantages/that the~ do not need any solvent ~or impregnating the substrate and may be cured without generating any bubble ~orming gas and thus without applying substantial pressure.
- 2 -- ` ' :
l~ss~7n According to -the present invention, a process for producing electrica:l lami~lates is provided compr:ising the steps o~ :Lmpregnating a ~ibrous substrate with an unsaturated polyester regin which i9 liquicl at room temperature, lamina-t-ing a plurality o~ the resin-impregnated gubstrates to form a unitary member, sandwiching the laminate between a pair o~
covering sheets, and curing the laminate. The improvement resides in that at least one o~ said pair o~ covering sheets i9 generall~ ~lexible but has a rigidity as de~ined by the value E-d3kg-cm, wherein E is the ~lexural modulus in kg/cm2 and d is the thickness in cm, of greater than 3 x lO~ kg-cm, pre~erably greater than 5 x lO 1 kg-cm. This enables to give smooth sur~ace characteristics to the laminate after stripping said one of covering sheets.
I~ desired, a conventional cladding metal foil such as electrolytic copper roils may be used on the other side o~
said pair o~ covering sheets to produce a clad laminate.
It is pre~erable that the uncured laminate supported between said pair o~ covering sheets is cured by heating I
without substantial pressure and the overall steps are carried out in a continuous manner.
Any con~entional unsaturated polyes-ter resin composi-tion which is a liquid at room temperature may be used.
The resin composition compriseg an unsaturated poly-ester and a cross-linking vinyl monomer. As is well-known in the art, the unsaturated polye~ters are ~ reaction product~o~
8~
-- 4 ~
(a) a polyhydric alcohol such as ethyleneglycol, propylene-glycol, diethyleneglycol, 1,4-butanediol, or 1,5-pentanediol with (b) an unsaturated~polycarboxylic acid such as maleic anhydride or fuma-ric acid, and (c) a saturated polycarboxylic acid such as phthalic anhydride, isophthalic acid, terephthalic acid, adipic acid, sebatic acid or azelaic acid. The condensate typically has a recurring unit of the formula:
~ O O O O ~
--fC2H4-0-C~ C-O-C2H4-0-C-CH=CH-C--Examples of the cross-linking vinyl monomer include styrene, a-methylstyrene, vinyltoluene, chlorostyrene, divinyl-benzene, Cl-C10 alkyl acrylates, Cl-C10 alkyl methacrylates, di-allyl phthalate, triallyl cyanurate and the like. Styrene is pre-ferable. The resin composition preferably contains about 20 to 50 weight % of the monomer in the entire resin composition and has a viscosity of 0.1 to 30 poise, preferably 2 to 10 poise at room temperature. Preferably the resin composition cures at a tempera-ture from 60C to 170C.
The liquid polyester resins may contain a curing : catalyst and a curing accelerator. The~curing catalyst may be of the organic peroxide type, the photosensitive type or the radiation i - : ~
~ ~.ensit~ve type but oryanic.peroxide typ~ IS mos:t preferable~ Prefer-.
able examplesof an organic peroxide catalyst include di-t-butylperoxide, 2,5-dimethyl-2,~5-di~t-butylperoxy) hexane, .
, ' / ,' " ':
, 7 n acetyl peroxide, isobutyryl peroxide, t~butylperoxy-2-ethyl-hexanoate, t-butylperoxyacetate, t-butylperoxyisobutyrate, t-buty.tperox~-2-ethylhexanoate, t-butylperox~laurate, etc.
Conventional curing acceIators such as cobalt compounds may be used.
A variety of fibrous substrates may be used. Usable substrates include woven or nonwoven fabrics made of natural or synthetic~ inorganic or organic fibers such as glass fiber fabrics, or papers made of kraft pulp or cotton linter pulp.
A~ter impregnating the substrate with the liquid resin, a plurality of the impregnated substrates are laminated together, sandwiched between a pair of covering sheets and cured. Experiments have shown, however, that the surface characteristics of the resulting laminate are often not satisfactory after stripping the covering sheet. This is because the surface characteristics of the starting substrate are not smooth enough and substantial pressure is needed when the laminate is sandwiched between the covering sheets. When the covering sheets are soft enough and especially:when the laminate is cured while being supported between the covering sheets wi-thout substantial pressure, the finished laminate : tend.s to assume the rough surface characteristics of the starting substrate.
According to the present invention, excellent smooth surface characteristics may be obtained by using as said covering sheet a.film or sheet like material having a rigidity 7 n as defined by E-d3 kg cm of greater than 3 x 10-3 kg-cm.
The covering ~heet is, however, preferablr flexible suffi-cient to permit strlpping :Lt from the cur0d latninate and taki.ng up on a roll or circulating as an endless balt.
The covering sheet preferablr has a surface roughness R max of less than 15~m~ preferablr from 0.4 to 9~m. The surface roughness R max used herein refers to the~m~m_ height of rou~hness measured according to JIS B 0601 by a stylus tracing tester under the conditions of 2.5~m radius of curvature o~ strlus tip and O.lg weight the stylus tip.
This surface roughness is related to the top finish of the resulting laminate aPter the covering sheet has been .peeled o:~f. Thus top finish of the finished laminate may be varied ~rom a lusterous top finish to a lusterless top finish by suitably selecting the R max value within said range.
Experiments have shown that a roughness R m x of at least Pr~ .b`l1ai+?,~
O.4~m is needed for imparting good ~$~L~ to the top surface of the resulting laminate. Excessive roughnes~
values ~e,of course, adversely a~fect on the performance of the laminate.
Unclad laminates are produced by placing the covering sheets each having said rigidity value on both sides of the uncured laminate. Metal foil clad laminates are produced by placing said covering sheet having the mentioned rigidity ; 25 value on one side of the laminate and a metal foil such as copper foll on the other ~ide.
' ~.
1~58~7(~
The curing s-tep may be carried out by heating the entire structure :~or a length of time. Since the resin composltion does not evolve any gaseous product upon curing, no pressure is needed during the curing step. Rather, pres-sure should be avoided as it often causes the liquid resin to be squ0e~ed out or internal strain to occur and thus cli rn el~l S~ ~na 1 - .
impairs the ~m~i~n stability of the finished laminate.
In a preferred embodiment of the invention, a kra~t or cotton linter paper having a thickness from 200 to 300~m and a basis weight o* about 150 g/m2 may be used. The sur-fac0 o~ this paper is microscopically rough. Experiments have shown that the finished laminate produced from this paper did not have satisfactorily smooth surface characteristics when a polyester film having a flexural modulus of 28,100 kg/cm2 and a thickness of 35~m (E-d3=1.20 x 10 3 kg-cm) was used as the covering sheet. By using a covering sheet having a rigidity value greater than 3 x 10 3 kg-cm, satisfactorily smooth surface characteristics may be obtained.
Examples of the usable covering sheets include a polyester film having a thickness of lOO~m (E-d3=2.81 x 10 2), an aluminum foil of lOO~m thick (E=0.67 x 106 kg/cm2, E-d3=
6.7 x 10 kg-cm), a stainless steel foil (E=1.86 x 106, E-d3=1.86 kg-cm) and -the like. The covering sheet may be of single ply or a multiply composite sheet.
The rigidity of a material generally decreases with the increase of temperature. Accordingly, those materials ~ l~s~7n whose rigidit~ decreases rapidly upon heating to the curing temperature o-~ the unsaturated polyester resin are not pref-erable. Also, :Lt is not pre:~erable for the material to have a strong adheslon to the polyester resin. ~'or these reasons, preferable materials for the covering sheet are cellophane, polyester, polypropylene, teflon, polyamide, aluminum, stain-less steel, copper and the like. Pol~imide film, for example, is not preferable. Usually the covering gheets made o~ these materials may be easily stripped from the laminate a~ter cur-ing without using any mold release although the use thereo~
is not excluded.
The process o-f the present invention is highly adapted Dr~ccss ~or carring out the entire ~ s in a continuous manner. In this instance the covering sheet is supplied and placed on the uncured laminate ~rom a suppl~ roll and is taken up on a ; take-up roll. ~lternatively, the covering sheet may be placed in the form of an endless belt which moves at the same speed as the laminate runs while ~ g in contact with the laminate.
For this reason, the covering sheet should not be too rigid or too stiff. A rigidity E-d3 of 3 x 10 kg-cm is genèrally the upper limit.
~lectrical laminates require higher performance characteristics -such as heat resistance, fireproofness, ~i men S~D~/
~h~n~n stability, moisture resistance, punchabilit~, clad peeling strength, electric insulation propert~ and the like.
The resin composition used in the present invention may 1 ls~7n contain various additives and the ibrous substrate may be subjected to various preliminary treatment steps to improve these characteristics.
The present invention is further illustrated by the following examples in which all parts and percentages are by weight.
A curable liquid resin composition was prepared by admixi,ng 100 parts of a commercially available unsaturated polyester resin having a viscosity at 23C of 5 poise (RIGOLAC
150 HR, trade mark sold by Showa Kobunshi Co.), 1 parts of t-butylperoxy-2-ethylhexanoate and 0.2 parts of 6% cobalt naph-thenate. A commercially available kraft paper (MKP-150, txade mark sold by Tomoegawa Paper Co.) was impregnated with the above liquid resin. Two plies of the impregnated paper sub~
strate were laminated together by passing between a pair of -rollers and excessive liquid resin was s~ueezed. Then the re-sulting laminate was sandwiched between two sheets of a luster-.
less polyester film each having a thickness of lOO~m, a rigidity E-d3 of 2.81 x 10 2 kg.cm, and R max of 4.3~m. The entire struc-ture was heated to 100C for 30 minutes and then main~ained at 85C for 13 hours to cure the laminate. After stripping the polyester sheets, the finished laminate possessed excellent smooth surface characteristics. The laminate had a thickness 520~m and a grade corresponding to NEMA standard XPC.
.: ~ . .
' .' ' ~": . , ~ ;
: ~
` 1 1~8~7~
As a control, a polyester film of 35~m thick (E d3=
1.20 x 10 3 ]cg.cm, R max=0.3~Lm) replaced the lOO~Lm thick film in the above process. The resulting laminate possessed micro-scopically rough surface characteristics similar to the sur-face of the starting paper substrate.
The process of Example 1 was repeated except than an aluminum foil having a thickness of lOO~Lm, a rigidlty E-d3 of 6.7 x 10 1 kg.cm, and R max of 0.5~m replaced polyester film.
The aluminum foil was easily stripped to give excellent smooth surface characteristics as in Example 1.
The process of Example 1 was repeated except that a stainless steel foil having a thickness of lOO~m, a rigidity E d3 of 1.86 kg.cm, and R max of 2.4~Lm replaced the polyester film. The stainless steel foil was easily stripped to give excellent smooth surface characteristics as in Example 1.
A kraft paper was impregnated with a liquid unsatur-ated polyester resin composition as in Example 1 by castingthe liquid resin onto the upper side of the paper substrate.
Five plies of the resin impregnated substrate were laminated together by passing between a pair of oppositely rotating rollers and excessive resin was squeezed out. Then the lami-25 nate was sandwiched by continuously placing an - -~ 15~7() electrol~tic copper ~oil ~ 35~m thick on the upper side and a stainless steel ~oil ~ lOO~m thick on the lower side.
The sandwich was then heated to 100~ ~cq~r~g ~or 30 minutes br continuously passing through an oven. A~ter gtripping the stainless steel ~oil and cutting into a suitable size, the resulting copper clad laminate possessed excellent smooth sur~ace characteristics and printabilitr.
The above has been of~ered for illustrative purposes only, and it is not ~or the,~purpose o~ limiting the scope o~
this invention, which is de~ined in the claims below.
' : ' ' .;
l~ss~7n According to -the present invention, a process for producing electrica:l lami~lates is provided compr:ising the steps o~ :Lmpregnating a ~ibrous substrate with an unsaturated polyester regin which i9 liquicl at room temperature, lamina-t-ing a plurality o~ the resin-impregnated gubstrates to form a unitary member, sandwiching the laminate between a pair o~
covering sheets, and curing the laminate. The improvement resides in that at least one o~ said pair o~ covering sheets i9 generall~ ~lexible but has a rigidity as de~ined by the value E-d3kg-cm, wherein E is the ~lexural modulus in kg/cm2 and d is the thickness in cm, of greater than 3 x lO~ kg-cm, pre~erably greater than 5 x lO 1 kg-cm. This enables to give smooth sur~ace characteristics to the laminate after stripping said one of covering sheets.
I~ desired, a conventional cladding metal foil such as electrolytic copper roils may be used on the other side o~
said pair o~ covering sheets to produce a clad laminate.
It is pre~erable that the uncured laminate supported between said pair o~ covering sheets is cured by heating I
without substantial pressure and the overall steps are carried out in a continuous manner.
Any con~entional unsaturated polyes-ter resin composi-tion which is a liquid at room temperature may be used.
The resin composition compriseg an unsaturated poly-ester and a cross-linking vinyl monomer. As is well-known in the art, the unsaturated polye~ters are ~ reaction product~o~
8~
-- 4 ~
(a) a polyhydric alcohol such as ethyleneglycol, propylene-glycol, diethyleneglycol, 1,4-butanediol, or 1,5-pentanediol with (b) an unsaturated~polycarboxylic acid such as maleic anhydride or fuma-ric acid, and (c) a saturated polycarboxylic acid such as phthalic anhydride, isophthalic acid, terephthalic acid, adipic acid, sebatic acid or azelaic acid. The condensate typically has a recurring unit of the formula:
~ O O O O ~
--fC2H4-0-C~ C-O-C2H4-0-C-CH=CH-C--Examples of the cross-linking vinyl monomer include styrene, a-methylstyrene, vinyltoluene, chlorostyrene, divinyl-benzene, Cl-C10 alkyl acrylates, Cl-C10 alkyl methacrylates, di-allyl phthalate, triallyl cyanurate and the like. Styrene is pre-ferable. The resin composition preferably contains about 20 to 50 weight % of the monomer in the entire resin composition and has a viscosity of 0.1 to 30 poise, preferably 2 to 10 poise at room temperature. Preferably the resin composition cures at a tempera-ture from 60C to 170C.
The liquid polyester resins may contain a curing : catalyst and a curing accelerator. The~curing catalyst may be of the organic peroxide type, the photosensitive type or the radiation i - : ~
~ ~.ensit~ve type but oryanic.peroxide typ~ IS mos:t preferable~ Prefer-.
able examplesof an organic peroxide catalyst include di-t-butylperoxide, 2,5-dimethyl-2,~5-di~t-butylperoxy) hexane, .
, ' / ,' " ':
, 7 n acetyl peroxide, isobutyryl peroxide, t~butylperoxy-2-ethyl-hexanoate, t-butylperoxyacetate, t-butylperoxyisobutyrate, t-buty.tperox~-2-ethylhexanoate, t-butylperox~laurate, etc.
Conventional curing acceIators such as cobalt compounds may be used.
A variety of fibrous substrates may be used. Usable substrates include woven or nonwoven fabrics made of natural or synthetic~ inorganic or organic fibers such as glass fiber fabrics, or papers made of kraft pulp or cotton linter pulp.
A~ter impregnating the substrate with the liquid resin, a plurality of the impregnated substrates are laminated together, sandwiched between a pair of covering sheets and cured. Experiments have shown, however, that the surface characteristics of the resulting laminate are often not satisfactory after stripping the covering sheet. This is because the surface characteristics of the starting substrate are not smooth enough and substantial pressure is needed when the laminate is sandwiched between the covering sheets. When the covering sheets are soft enough and especially:when the laminate is cured while being supported between the covering sheets wi-thout substantial pressure, the finished laminate : tend.s to assume the rough surface characteristics of the starting substrate.
According to the present invention, excellent smooth surface characteristics may be obtained by using as said covering sheet a.film or sheet like material having a rigidity 7 n as defined by E-d3 kg cm of greater than 3 x 10-3 kg-cm.
The covering ~heet is, however, preferablr flexible suffi-cient to permit strlpping :Lt from the cur0d latninate and taki.ng up on a roll or circulating as an endless balt.
The covering sheet preferablr has a surface roughness R max of less than 15~m~ preferablr from 0.4 to 9~m. The surface roughness R max used herein refers to the~m~m_ height of rou~hness measured according to JIS B 0601 by a stylus tracing tester under the conditions of 2.5~m radius of curvature o~ strlus tip and O.lg weight the stylus tip.
This surface roughness is related to the top finish of the resulting laminate aPter the covering sheet has been .peeled o:~f. Thus top finish of the finished laminate may be varied ~rom a lusterous top finish to a lusterless top finish by suitably selecting the R max value within said range.
Experiments have shown that a roughness R m x of at least Pr~ .b`l1ai+?,~
O.4~m is needed for imparting good ~$~L~ to the top surface of the resulting laminate. Excessive roughnes~
values ~e,of course, adversely a~fect on the performance of the laminate.
Unclad laminates are produced by placing the covering sheets each having said rigidity value on both sides of the uncured laminate. Metal foil clad laminates are produced by placing said covering sheet having the mentioned rigidity ; 25 value on one side of the laminate and a metal foil such as copper foll on the other ~ide.
' ~.
1~58~7(~
The curing s-tep may be carried out by heating the entire structure :~or a length of time. Since the resin composltion does not evolve any gaseous product upon curing, no pressure is needed during the curing step. Rather, pres-sure should be avoided as it often causes the liquid resin to be squ0e~ed out or internal strain to occur and thus cli rn el~l S~ ~na 1 - .
impairs the ~m~i~n stability of the finished laminate.
In a preferred embodiment of the invention, a kra~t or cotton linter paper having a thickness from 200 to 300~m and a basis weight o* about 150 g/m2 may be used. The sur-fac0 o~ this paper is microscopically rough. Experiments have shown that the finished laminate produced from this paper did not have satisfactorily smooth surface characteristics when a polyester film having a flexural modulus of 28,100 kg/cm2 and a thickness of 35~m (E-d3=1.20 x 10 3 kg-cm) was used as the covering sheet. By using a covering sheet having a rigidity value greater than 3 x 10 3 kg-cm, satisfactorily smooth surface characteristics may be obtained.
Examples of the usable covering sheets include a polyester film having a thickness of lOO~m (E-d3=2.81 x 10 2), an aluminum foil of lOO~m thick (E=0.67 x 106 kg/cm2, E-d3=
6.7 x 10 kg-cm), a stainless steel foil (E=1.86 x 106, E-d3=1.86 kg-cm) and -the like. The covering sheet may be of single ply or a multiply composite sheet.
The rigidity of a material generally decreases with the increase of temperature. Accordingly, those materials ~ l~s~7n whose rigidit~ decreases rapidly upon heating to the curing temperature o-~ the unsaturated polyester resin are not pref-erable. Also, :Lt is not pre:~erable for the material to have a strong adheslon to the polyester resin. ~'or these reasons, preferable materials for the covering sheet are cellophane, polyester, polypropylene, teflon, polyamide, aluminum, stain-less steel, copper and the like. Pol~imide film, for example, is not preferable. Usually the covering gheets made o~ these materials may be easily stripped from the laminate a~ter cur-ing without using any mold release although the use thereo~
is not excluded.
The process o-f the present invention is highly adapted Dr~ccss ~or carring out the entire ~ s in a continuous manner. In this instance the covering sheet is supplied and placed on the uncured laminate ~rom a suppl~ roll and is taken up on a ; take-up roll. ~lternatively, the covering sheet may be placed in the form of an endless belt which moves at the same speed as the laminate runs while ~ g in contact with the laminate.
For this reason, the covering sheet should not be too rigid or too stiff. A rigidity E-d3 of 3 x 10 kg-cm is genèrally the upper limit.
~lectrical laminates require higher performance characteristics -such as heat resistance, fireproofness, ~i men S~D~/
~h~n~n stability, moisture resistance, punchabilit~, clad peeling strength, electric insulation propert~ and the like.
The resin composition used in the present invention may 1 ls~7n contain various additives and the ibrous substrate may be subjected to various preliminary treatment steps to improve these characteristics.
The present invention is further illustrated by the following examples in which all parts and percentages are by weight.
A curable liquid resin composition was prepared by admixi,ng 100 parts of a commercially available unsaturated polyester resin having a viscosity at 23C of 5 poise (RIGOLAC
150 HR, trade mark sold by Showa Kobunshi Co.), 1 parts of t-butylperoxy-2-ethylhexanoate and 0.2 parts of 6% cobalt naph-thenate. A commercially available kraft paper (MKP-150, txade mark sold by Tomoegawa Paper Co.) was impregnated with the above liquid resin. Two plies of the impregnated paper sub~
strate were laminated together by passing between a pair of -rollers and excessive liquid resin was s~ueezed. Then the re-sulting laminate was sandwiched between two sheets of a luster-.
less polyester film each having a thickness of lOO~m, a rigidity E-d3 of 2.81 x 10 2 kg.cm, and R max of 4.3~m. The entire struc-ture was heated to 100C for 30 minutes and then main~ained at 85C for 13 hours to cure the laminate. After stripping the polyester sheets, the finished laminate possessed excellent smooth surface characteristics. The laminate had a thickness 520~m and a grade corresponding to NEMA standard XPC.
.: ~ . .
' .' ' ~": . , ~ ;
: ~
` 1 1~8~7~
As a control, a polyester film of 35~m thick (E d3=
1.20 x 10 3 ]cg.cm, R max=0.3~Lm) replaced the lOO~Lm thick film in the above process. The resulting laminate possessed micro-scopically rough surface characteristics similar to the sur-face of the starting paper substrate.
The process of Example 1 was repeated except than an aluminum foil having a thickness of lOO~Lm, a rigidlty E-d3 of 6.7 x 10 1 kg.cm, and R max of 0.5~m replaced polyester film.
The aluminum foil was easily stripped to give excellent smooth surface characteristics as in Example 1.
The process of Example 1 was repeated except that a stainless steel foil having a thickness of lOO~m, a rigidity E d3 of 1.86 kg.cm, and R max of 2.4~Lm replaced the polyester film. The stainless steel foil was easily stripped to give excellent smooth surface characteristics as in Example 1.
A kraft paper was impregnated with a liquid unsatur-ated polyester resin composition as in Example 1 by castingthe liquid resin onto the upper side of the paper substrate.
Five plies of the resin impregnated substrate were laminated together by passing between a pair of oppositely rotating rollers and excessive resin was squeezed out. Then the lami-25 nate was sandwiched by continuously placing an - -~ 15~7() electrol~tic copper ~oil ~ 35~m thick on the upper side and a stainless steel ~oil ~ lOO~m thick on the lower side.
The sandwich was then heated to 100~ ~cq~r~g ~or 30 minutes br continuously passing through an oven. A~ter gtripping the stainless steel ~oil and cutting into a suitable size, the resulting copper clad laminate possessed excellent smooth sur~ace characteristics and printabilitr.
The above has been of~ered for illustrative purposes only, and it is not ~or the,~purpose o~ limiting the scope o~
this invention, which is de~ined in the claims below.
' : ' ' .;
Claims (9)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a process for producing electrical laminates comprising the steps of impregnating a fibrous substrate with an unsaturated polyester resin which is a liquid at room temperature, laminating a plurality of the resin-impregnated substrates to form a unitary member, sandwiching the laminate between a cladding metal foil and a covering sheet, curing the same, and stripping said covering sheet, the improvement comprising employing as said covering sheet a generally flexible, peelable covering sheet having a rigidity as defined by the value E.d3[kg.cm], wherein E
is the flexural modulus in kg/cm2 and d is the thickness in cm, of greater than 3 x 10-3kg.cm and having a surface roughness R max of less than 15µm when measured according to JIS B 0601 using a stylus tracing tester having a stylus tip having a radius of curvature of 2.5µm and a weight of 0.lg, such that a smooth surface of the finished laminate is obtained after stripping said covering sheet.
is the flexural modulus in kg/cm2 and d is the thickness in cm, of greater than 3 x 10-3kg.cm and having a surface roughness R max of less than 15µm when measured according to JIS B 0601 using a stylus tracing tester having a stylus tip having a radius of curvature of 2.5µm and a weight of 0.lg, such that a smooth surface of the finished laminate is obtained after stripping said covering sheet.
2. The process according to claim 1, wherein said rigidity value is less than 3 x 10kg.cm.
3. The process according to claim 1, wherein said surface roughness ranges from 0.4 to 9.0µm.
4. The process according to claim 1, wherein said covering sheet is made of polyester, aluminum or stainless steel.
5. The process according to claim 1, wherein the entire process is carried out in a continuous manner.
6. The process according to claim 5, wherein said covering sheet is continuously supplied from and taken up in a roll.
7. The process according to claim 5, wherein said covering sheet takes the form of an endless belt.
8. The process according to claim 1, wherein said fibrous substrate is paper.
9. The process of claim 1 wherein said covering sheet is peeled off said laminate to produce a lusterless top finish on said laminate.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000367819A CA1158970A (en) | 1980-12-31 | 1980-12-31 | Production of electrical laminates |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000367819A CA1158970A (en) | 1980-12-31 | 1980-12-31 | Production of electrical laminates |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1158970A true CA1158970A (en) | 1983-12-20 |
Family
ID=4118816
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000367819A Expired CA1158970A (en) | 1980-12-31 | 1980-12-31 | Production of electrical laminates |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1158970A (en) |
-
1980
- 1980-12-31 CA CA000367819A patent/CA1158970A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |