JP2012169680A - Printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printed wiring board permitting high-density storage in an electronic equipment case.SOLUTION: The printed wiring board includes a substrate having flexibility, and a conductor formed on at least one side of the substrate. The printed wiring board has a bending region to be bent, and a non-bending region not to be bent. The thickness of a conductor formed in the bending region is 1-30 μm, and the thickness of a conductor formed in the non-bending region is 30-150 μm. The thickness of the conductor formed in the non-bending region is larger than the thickness of the conductor formed in the bending region. The thickness of the conductor formed in the bending region is 6-60% of the thickness of the conductor formed in the non-bending region.

Description

  The present invention relates to a printed wiring board.

  A laminated board for a printed wiring board can be obtained by stacking a predetermined number of prepregs having a resin composition having electrical insulation as a matrix, and heating and pressing to integrate them. In the production of a printed wiring board, when a printed circuit is formed by a subtractive method, a metal-clad laminate is used. This metal-clad laminate is manufactured by stacking a metal foil such as a copper foil on the surface (one side or both sides) of the prepreg and heating and pressing.

  Thermosetting resins such as phenol resin, epoxy resin, polyimide resin, bismaleimide-triazine resin, etc. are widely used as the resin having electrical insulation. In addition, a thermoplastic resin such as a fluororesin or a polyphenylene ether resin may be used.

  On the other hand, with the widespread use of information terminal devices such as personal computers and mobile phones, printed wiring boards mounted on them are becoming smaller and higher in density. The mounting form has progressed from a pin insertion type to a surface mounting type, and further to an area array type represented by a BGA (ball grid array) using a plastic substrate.

  In a substrate on which a bare chip such as a BGA is directly mounted, the chip and the substrate are generally connected by wire bonding by thermosonic bonding. For this reason, the substrate on which the bare chip is mounted is exposed to a high temperature of 150 ° C. or higher, and the electrically insulating resin needs a certain degree of heat resistance.

  Further, in such a substrate, there is a case where so-called repairability in which a chip once mounted is removed is also required. In this case, the same level of heat as that applied during chip mounting is applied, and then the chip mounting is again performed on the substrate, and further heat treatment is performed. Therefore, in a substrate that requires repairability, cyclic thermal shock resistance at high temperatures is also required. In the conventional insulating resin, peeling may occur between the fiber base material and the resin.

  Therefore, in a printed wiring board, a prepreg impregnated with a resin composition containing polyamideimide as an essential component in a fiber substrate is used in order to improve fine wiring formability in addition to thermal shock resistance, reflow resistance, and crack resistance. It has been proposed (for example, see Patent Document 1). In addition, a heat-resistant base material in which a fiber base material is impregnated with a resin composition composed of a silicone-modified polyimide resin and a thermosetting resin has been proposed (for example, see Patent Document 2).

  Furthermore, with the miniaturization and high performance of electronic devices, it has become necessary to house printed wiring boards with component mounting in a more limited space. For this purpose, a method of arranging a plurality of printed wiring boards in multiple stages and connecting each other with a wire harness or a flexible wiring board is used (for example, see Patent Document 3). In addition, a rigid-flex substrate in which a flexible substrate based on polyimide and a conventional rigid substrate are multilayered may be used (for example, see Patent Document 4).

JP 2003-55486 A JP-A-8-193139 JP 2002-064271 A JP-A-6-302962

  In the above-mentioned conventional printed wiring board, an extra space is required because the printed wiring board is connected by a wire harness or a flexible wiring board, or the flexible board and the rigid board are multilayered. Densification is difficult to achieve.

  Therefore, the present invention has been made in view of such circumstances, and an object thereof is to provide a printed wiring board that can be stored in a high density in a casing of an electronic device.

  In order to achieve the above object, a printed wiring board of the present invention is a printed wiring board comprising a base material having flexibility and a conductor formed on at least one side of the base material, and is a bent region to be bent. The conductor formed in the bent region has a thickness of 1 to 30 μm, and the conductor formed in the non-bent region has a thickness of 30 to 150 μm.

  Here, the bent region is a portion that is bent when the printed wiring board is accommodated. On the other hand, a non-bent region that is not bent is a portion that is not bent when the printed wiring board is accommodated. For example, a region that is unintentionally stressed in the bending direction is substantially bent. It is considered that it is not, and corresponds to a non-bending area.

  Thus, in the printed wiring board of the present invention, the thickness of the conductor in the bent portion is 1 to 30 μm and the thickness of the conductor in the non-bent portion is 30 to 150 μm, so that the integrated printed wiring board can be used. The structure includes both a flexible part and a rigid part. Since the printed wiring board having such a configuration can be easily bent at a flexible portion, the printed wiring board can be stored in a space such as an electronic device at a high density.

  In the printed wiring board of the present invention, it is preferable that the thickness of the conductor formed in the non-bent region is larger than the thickness of the conductor formed in the bent region. Such a printed wiring board of the present invention can easily have a non-flexible portion in a flexible printed wiring board only by changing the thickness of a conductor usually made of a highly rigid metal or the like. For this reason, a structure becomes simple compared with the conventional rigid-flexible wiring board which combines a rigid wiring board and a flexible wiring board. Further, since the rigid property is expressed by the metal having high rigidity, it is possible to reduce the thickness as compared with the conventional rigid-flexible wiring board. As a result, when stored in an electronic device or the like, it can be efficiently stored in a limited space.

  That is, the printed wiring board of the present invention is a printed wiring board comprising a base material having flexibility and a conductor formed on the base material, and is a bent region to be bent, and substantially bent. The thickness of the conductor formed in the bent region is smaller than the thickness of the conductor formed in the bent region.

  In the printed wiring board of the present invention, the thickness of the conductor formed in the bent region is preferably 6 to 60% of the thickness of the conductor formed in the non-bent region. If it carries out like this, a non-bending area | region can maintain favorable rigidity, while a bending area | region has the favorable flexibility. As a result, the reliability of the printed wiring board is improved.

  More specifically, it is preferable that the conductor formed in the bent region has a thickness of 1 to 30 μm by etching. Moreover, the conductor formed in the non-bending region is preferably one having a thickness of 30 to 150 μm by plating. As a result, the conductors in the bent region and the non-bent region are each well prepared to have a suitable thickness, and these regions are likely to have desired flexibility and rigidity, respectively.

  In the printed wiring board of the present invention, the substrate preferably includes a fiber substrate, and the fiber substrate is a glass cloth having a thickness of 50 μm or less. A base material including such a fiber base material can maintain a sufficient strength at a bent portion in spite of being thin, and has excellent dimensional stability. Therefore, a printed wiring board provided with such a base material is thin and easy to bend in a bending region, so that it can be more easily stored at a high density.

  Moreover, it is more preferable that a base material contains a thermosetting resin composition as a matrix. In particular, it is preferable to contain the thermosetting resin composition in a cured state. Such a substrate has excellent heat resistance in addition to excellent electrical insulation.

  Specifically, the thermosetting resin composition preferably contains at least one of a resin having a glycidyl group, a resin having an amide group, and an acrylic resin. A base material containing such a thermosetting resin composition has good mechanical strength and flexibility in addition to heat resistance and electrical insulation, and can improve the strength and flexibility of the printed wiring board.

  The printed wiring board according to the present invention includes a rigid portion and a flexible portion in an integral structure by having conductors having a predetermined thickness in the bent region and the non-bent region, respectively, so that a conventional rigid-flex board is provided. In addition to being able to achieve a significant reduction in thickness, no extra space is required. Therefore, the electronic device can be stored at a high density even in a limited space. Moreover, since the base material is also integrated, the resin component constituting the base material can be made single, and it can have excellent heat resistance, mechanical strength, and impact resistance. Furthermore, when the fiber base material is included in the base material, the fiber base material is also included in the bent region, the strength of the bent portion is sufficiently maintained, and the dimensional stability is excellent.

It is process sectional drawing which shows typically the process of etching the conductor formed in the bending area | region. It is process sectional drawing which shows typically the process of plating on the conductor formed in the non-bending area | region.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

  First, the suitable manufacturing method for obtaining the printed wiring board of this invention is demonstrated. A printed wiring board is a copper including a fiber base material, a base material including a thermosetting resin composition having flexibility, and a conductor made of a copper foil having a predetermined thickness laminated on both surfaces of the base material. It is preferable to manufacture using a tension laminate. And in order to process this copper clad laminated board and obtain a printed wiring board, in the process of forming a circuit from a conductor, a method of etching a conductor formed in a bent area (bending area) of the printed wiring board, The conductors formed in both regions are made to have a desired thickness by a method of plating the conductors formed in the unbent region (non-bent region) of the printed wiring board. Hereinafter, these etching and plating methods will be described with reference to FIGS. 1 and 2, respectively.

(Method of etching the conductor formed in the bent area)
FIG. 1 is a process cross-sectional view schematically showing a process of etching a conductor formed in a bent region. First, as shown to Fig.1 (a), the base material 1 containing the thermosetting resin composition which has a fiber base material and a softness | flexibility, and the copper foil of thickness 18 micrometers laminated | stacked on the single side | surface of this base material 1 2 and a copper-clad laminate 30 including a copper foil 3 having a thickness of 70 μm laminated on the other surface of the substrate 1 is prepared.

  Next, as shown in FIG. 1B, an etching resist is laminated on the surfaces of the copper foil 2 and the copper foil 3 in the copper-clad laminate 30, and then an etching resist having a predetermined shape by a known photolithography process or the like. Pattern 4 is formed. At this time, the etching resist pattern 4 is shaped so that a desired circuit pattern can be obtained after the etching of the copper foils 2 and 3.

  Then, the copper foils 2 and 3 in the region where the etching resist pattern 4 is not formed are etched by a known copper etching method, and the copper foils 2 and 3 are processed into a predetermined pattern as shown in FIG. To do. Such etching is performed to such an extent that the copper foil 2 (thickness: 18 μm) in the region where the etching resist pattern 4 is not formed is completely removed. In this case, the region in the copper foil 3 having a thickness of 70 μm remains without being completely etched.

  Subsequently, as shown in FIG. 1D, an etching resist 5 is laminated on the side of the base material 1 where the copper foil 2 is formed so that the entire surface is covered. At this time, the etching resist pattern 4 remains formed on the surfaces of the copper foils 2 and 3. As a result, a region in the copper foil 3 where the etching resist pattern 4 is not formed is opened. This region becomes a bent region 36 when the printed wiring board 40 is used as will be described later.

  Thereafter, as shown in FIG. 1 (e), the copper foil 3 in the portion opened as described above is further etched to completely remove the copper foil in the portion 6 (flexibility imparting portion) to be a bent region. To do. Then, all the etching resists (etching resist pattern 4 and etching resist 5) are removed by a known resist stripping process. Accordingly, the printed wiring board 40 shown in FIG. 1 (f) including the conductor 7 formed in the bent region 36 and the conductor 8 and the conductor 9 formed in the non-bent region 46 on both surfaces of the substrate 1. Get.

  The printed wiring board 40 thus obtained has a bent region 36 having a total conductor thickness of 1 to 30 μm and a non-bent region 46 having a total conductor thickness of 30 to 150 μm. In addition, the total thickness of the conductor means the total thickness when having a plurality of conductors in the thickness direction, and means the thickness of only that conductor when having only one conductor in the thickness direction. To do. Therefore, in the above example, the thickness of the conductor formed in the bent region 36 is 18 μm, which is the thickness of the conductor 7, and the thickness of the conductor formed in the non-bent region 46 is 70 μm, which is the thickness of the conductor 9. Alternatively, the total thickness of the conductors 8 and 9 is 88 μm.

  As described above, in this method, after the conductor having a total thickness exceeding 30 μm formed on the base material is patterned into a predetermined shape, the patterned conductor is formed into a region to be a bent region. By etching the formed portion, a printed wiring board in which the conductors formed in the bent region and the non-bent region have a predetermined thickness can be obtained.

  In the above method, the conductive foils 2 and 3 are etched after patterning. However, the present invention is not limited to this, and the patterning may be performed after the copper foils 2 and 3 are etched. Further, in the above method, the copper foil 3 is completely removed by etching out of the copper foils 2 and 3 formed on both surfaces of the substrate 1, and only the copper foil 2 on one side having a desired thickness is left, Although the thickness of the conductor in the bent region is adjusted, for example, the total thickness of the conductor in the bent region portion may be adjusted within a desired range by appropriately etching both the copper foils 2 and 3. .

(Method of plating the conductor formed in the non-bent area)
FIG. 2 is a process cross-sectional view schematically showing a process of plating a conductor formed in a non-bent region. First, as shown to Fig.2 (a), the base material 1 containing the thermosetting resin composition which has a fiber base material and a softness | flexibility, and the copper foil of thickness 3 micrometers laminated | stacked on both surfaces of this base material 1 10 is prepared.

  Next, as shown in FIG. 2B, after forming a plating resist on both surfaces of the pair of copper foils 10 in the copper-clad laminate 50, a plating resist pattern having a predetermined shape by a known photolithography process or the like. 20 is formed. At this time, the plating resist pattern 20 is shaped so that a desired circuit pattern can be obtained by plating the copper foil 10.

  Then, as shown in FIG. 2 (c), the copper foil 10 on which the plating resist pattern 20 is formed is plated so as to have a predetermined thickness by electroplating, whereby the exposed surface of the copper foil 10 is plated. Copper 21 is formed.

  Subsequently, as shown in FIG. 2 (d), the plating resist is further laminated on both surfaces of the copper-clad laminate 50 in which the plated copper 21 is formed and the plating resist pattern 20 is formed. The plating resist pattern 24 is formed by patterning in such a shape that only the portion 22 (rigidity imparting portion) to be the non-bending region 66 is opened.

  Then, as shown in FIG.2 (e), it electroplats on the surface of the plating copper 21 in which the plating resist pattern 24 is not formed so that the thickness of the conductor after plating may be 30-150 micrometers, A plated copper 23 is further formed. Then, as shown in FIG. 2F, all the plating resists (plating resist pattern 20 and plating resist pattern 24) are removed by a known resist stripping process.

  And the copper foil 10 of the part in which the plated copper 21 and the plated copper 23 are not formed is removed by etching. As a result, the printed wiring board 60 shown in FIG. 2 (f) including the conductor 17 formed in the bent region and the conductor 18 and the conductor 19 formed in the non-bent region on both surfaces of the substrate 1 is obtained. .

  The printed wiring board 60 thus obtained has a bent region 56 in which the total thickness of the conductor (here, the thickness of the conductor 17) is 1 to 30 μm, and the total thickness of the conductor (the thickness of the conductor 19 alone, or , The total thickness of the conductors 18 and 19) has an unbent region 66 having a thickness of 30 to 150 μm.

  As described above, in this method, after the plated copper of a predetermined pattern is formed on the conductor formed on the substrate so as to have a total thickness of copper of 30 mm or less, the patterned plated copper By further plating the portion formed in the region to be the non-bending region, a printed wiring board in which the conductors formed in the bending region and the non-bending region have a predetermined thickness can be obtained.

  In addition, in said method, the plating for making the total thickness of the conductor in a non-bending area | region into 30-150 micrometers only on the conductor (copper foil 10 and plated copper 21) of the one side with respect to the base material 1. However, the present invention is not limited to this, and the substrate 1 formed in the non-bending region may be plated on the conductors on both sides. In the above method, after plating for pattern formation (plated copper 21), plating (plated copper 23) for adjusting the thickness of the conductor in the non-bent region is performed. The conductor may be patterned by performing adjustment plating and then etching the copper foil 10 after plating.

  As described above, as a preferable method for manufacturing a printed wiring board, a method for etching a conductor in a bent region and a method for plating a conductor in a non-bent region have been described separately. Both may be performed in That is, when manufacturing one printed wiring board, the conductor in the bent region may be etched and the conductor in the non-bent region may be plated. In this way, regardless of the thickness of the copper foil or the like that the copper-clad laminate initially has, the conductors in the bent region and the non-bent region can have a desired thickness.

  Next, a preferred configuration of the printed wiring board will be described in detail. Hereinafter, the printed wiring board 40 shown in FIG. 1F will be described as an example, but each configuration can be applied to the printed wiring board of the present invention without limitation.

  As shown in the figure, the printed wiring board 40 has the conductor 7 formed in the bent region 36 and the conductor 8 formed in the non-bent region 46 on one surface of the substrate 1, and on the other surface. In addition, the conductor 9 is formed in the non-bent region. As described above, in this printed wiring board 40, the total thickness of the conductor formed in the bent region 36 (the thickness of the conductor 7) is 1 to 30 μm, and the total thickness of the conductor formed in the non-bent region 46 (conductor 9). Or the total thickness of the conductors 8 and 9) is 30 to 150 μm.

  As described above, in the printed wiring board 40, since the conductors formed in the bent region 36 and the non-bent region 46 have the total thickness in the above range, the bending in the bent region 36 is facilitated. The non-bending region 46 can maintain sufficient rigidity. Therefore, the printed wiring board 40 can be stored at a high density by bending even in a limited space of an electronic device or the like. In particular, since this printed wiring board 40 is an integral one, there is no need for connection between the substrates and multi-layering as in the prior art. It also has high reliability.

  From the viewpoint of obtaining the effects as described above better, the total thickness of the conductors formed in the bent region 36 in the printed wiring board 40 is preferably 3 to 25 μm, and more preferably 8 to 20 μm. Moreover, the total thickness of the conductor formed in the non-bending region 46 is preferably 60 to 120 μm, and more preferably 70 to 100 μm. Thus, the total thickness of the conductor formed in the bent region 36 is preferably smaller than the total thickness of the conductor formed in the non-bent region 46. Specifically, the former is preferably 6 to 60% and more preferably 10 to 30% of the latter.

  The substrate 1 in the printed wiring board 40 is not limited to a fiber substrate as described above and a flexible thermosetting resin composition, and has flexibility and can be laminated with conductors. Anything can be used without particular limitation. For example, a polyimide film or an aramid film may be applied. However, from the viewpoint of obtaining excellent flexibility and strength, the substrate preferably includes a fiber substrate.

  As the fiber base material, any fiber base material such as a woven fabric or a non-woven fabric is preferable as long as it is used when producing a metal foil-clad laminate or a multilayer printed wiring board. Examples of the material of the fiber substrate include glass, alumina, boron, silica alumina glass, silica glass, tyrano, silicon carbide, silicon nitride, zirconia, and other inorganic fibers, aramid, polyether ether ketone, polyether imide, polyether. Examples thereof include organic fibers such as sulfone, carbon, and cellulose, or mixed papers thereof. Of these, a glass fiber woven fabric is preferable.

  In particular, when a prepreg is used as a material for forming the substrate 1, a glass cloth having a thickness of 50 μm or less is particularly suitable as the substrate used for the prepreg. By using such a glass cloth having a thickness of 50 μm or less, it becomes easy to obtain a printed wiring board that has flexibility and can be bent arbitrarily. It is also possible to reduce the dimensional change accompanying the temperature change and moisture absorption in the manufacturing process.

  The base material 1 is more preferable if the fiber base material contains an insulating resin rich in flexibility. That is, it is preferable to have a structure in which a fiber base material is arranged in an insulating resin. The insulating resin preferably includes a thermosetting resin composition, and more specifically includes a cured thermosetting resin composition. Examples of the thermosetting resin in the thermosetting resin composition include epoxy resins, polyimide resins, unsaturated polyester resins, polyurethane resins, bismaleimide resins, triazine-bismaleimide resins, and phenol resins.

  Especially, as a thermosetting resin contained in a thermosetting resin composition, resin which has a glycidyl group is preferable, resin which has a glycidyl group at the terminal is more preferable, and an epoxy resin is still more preferable. As the epoxy resin, polyglycidyl ether obtained by reacting polychlorophenol such as bisphenol A, novolac phenol resin, orthocresol novolac phenol resin or polyhydric alcohol such as 1,4-butanediol with epichlorohydrin, Polyglycidyl ester, amine, amide or N-glycidyl derivative of a compound having a heterocyclic nitrogen base obtained by reacting a polybasic acid such as phthalic acid or hexahydrophthalic acid with epichlorohydrin, an alicyclic epoxy resin, etc. Can be mentioned.

  Thus, when an epoxy resin is included as a thermosetting resin, the base material 1 can be cured at a temperature of 180 ° C. or less, and the base material 1 has thermal, mechanical and electrical characteristics. It tends to be good.

  In particular, when the thermosetting resin composition includes an epoxy resin as the thermosetting resin, it is more preferable to further include an epoxy resin curing agent or a curing accelerator. For example, an epoxy resin having two or more glycidyl groups and a curing agent thereof, an epoxy resin having two or more glycidyl groups and a curing accelerator, or an epoxy resin having two or more glycidyl groups, a curing agent, and a curing accelerator It can be a combination such as an agent. The more glycidyl groups the epoxy resin has, the better, and more preferably 3 or more. The suitable amount of the epoxy resin varies depending on the number of glycidyl groups, and the more glycidyl groups, the smaller the amount.

  The curing agent and curing accelerator for the epoxy resin are applicable without particular limitation as long as they can be cured by reacting with the epoxy resin and can accelerate curing, respectively. For example, amines, imidazoles, polyfunctional phenols, acid anhydrides and the like can be mentioned. Examples of amines include dicyandiamide, diaminodiphenylmethane, guanylurea and the like. Examples of the polyfunctional phenols include hydroquinone, resorcinol, bisphenol A or a halogen compound thereof, or a novolac type phenol resin or a resol type phenol resin that is a condensate with formaldehyde. Examples of acid anhydrides include phthalic anhydride, benzophenone tetracarboxylic dianhydride, methyl hymic acid, and the like. Moreover, as a hardening accelerator, alkyl group substituted imidazole, benzimidazole, etc. can be used as imidazoles.

  The preferred content of the curing agent or curing accelerator in the thermosetting resin composition is as follows. For example, in the case of amines, such an amount that the active hydrogen equivalent of the amine and the epoxy equivalent of the epoxy resin are approximately equal is preferable. In addition, in the case of imidazole which is a hardening accelerator, it is not simply an equivalent ratio with active hydrogen, and is preferably about 0.001 to 10 parts by weight with respect to 100 parts by weight of the epoxy resin. Moreover, in the case of polyfunctional phenols and acid anhydrides, the amount by which phenolic hydroxyl groups and carboxyl groups are 0.6 to 1.2 equivalents relative to 1 equivalent of epoxy resin is preferable.

  If the amount of the curing agent or curing accelerator is less than the preferred amount, an uncured epoxy resin remains after curing, and the Tg (glass transition temperature) of the cured thermosetting resin composition may be low. On the other hand, if it is too much, unreacted curing agent and curing accelerator remain after curing, and the insulating property of the thermosetting resin composition may be lowered.

  Moreover, as a thermosetting resin contained in the thermosetting resin composition in the base material 1, a high molecular weight resin component may be contained for the purpose of improving flexibility and heat resistance. Examples of such thermosetting resins include resins having amide groups and acrylic resins.

  First, as the resin having an amide group, a polyamideimide resin is preferable, and a siloxane-modified polyamideimide having a structure including a siloxane structure is particularly preferable. This siloxane-modified polyamideimide is composed of a diamine having two or more aromatic rings (hereinafter referred to as “aromatic diamine”) and a mixture containing diimide dicarboxylic acid obtained by reacting a mixture of siloxane diamine and trimellitic anhydride. Particularly preferred are those obtained by reacting with an aromatic diisocyanate.

  The polyamideimide resin preferably contains 70 mol% or more of polyamideimide molecules containing 10 or more amide groups in one molecule. The range of the content of this polyamideimide molecule can be obtained, for example, from the chromatogram obtained from GPC of polyamideimide and the mol number (A) of amide groups in the unit weight of polyamideimide obtained separately. Specifically, first, from the number of moles of amide groups (A) contained in polyamideimide (a) g, the molecular weight (C) of polyamideimide containing 10 amide groups per molecule of 10 × a / A. Suppose that And, when the region where the number average molecular weight of the chromatogram obtained by GPC is C or more is 70% or more, “contains 70 mol% or more of polyamideimide molecules containing 10 or more amide groups in one molecule” Judge. As a method for determining the amide group, NMR, IR, hydroxamic acid-iron color reaction method, N-bromoamide method and the like can be used.

  The siloxane-modified polyamideimide having a structure containing a siloxane structure is preferably a mixture ratio of aromatic diamine a and siloxane diamine b, preferably a / b = 99.9 / 0.1 to 0/100 (molar ratio). It is preferable that a / b = 95/5 to 30/70, more preferably a / b = 90/10 to 40/60. When the mixing ratio of siloxane diamine b increases, Tg tends to decrease. On the other hand, when it decreases, the amount of varnish solvent remaining in the resin tends to increase when a prepreg is produced.

  Examples of the aromatic diamine include 2,2-bis [4- (4-aminophenoxy) phenyl] propane (BAPP), bis [4- (3-aminophenoxy) phenyl] sulfone, and bis [4- (4- Aminophenoxy) phenyl] sulfone, 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, bis [4- (4-aminophenoxy) phenyl] methane, 4,4′-bis (4- Aminophenoxy) biphenyl, bis [4- (4-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] ketone, 1,3-bis (4-aminophenoxy) benzene, 1,4- Bis (4-aminophenoxy) benzene, 2,2'-dimethylbiphenyl-4,4'-diamine, 2,2'-bis (trifluoro Til) biphenyl-4,4'-diamine, 2,6,2 ', 6'-tetramethyl-4,4'-diamine, 5,5'-dimethyl-2,2'-sulfonyl-biphenyl-4,4 '-Diamine, 3,3'-dihydroxybiphenyl-4,4'-diamine, (4,4'-diamino) diphenyl ether, (4,4'-diamino) diphenyl sulfone, (4,4'-diamino) benzophenone, Examples thereof include (3,3′-diamino) benzophenone, (4,4′-diamino) diphenylmethane, (4,4′-diamino) diphenyl ether, (3,3′-diamino) diphenyl ether, and the like.

  Examples of the siloxane diamine include those represented by the following general formulas (3) to (6). In the following formula, n and m each represent an integer of 1 to 40.

  In addition, as siloxane diamine represented by the said General formula (3), X-22-161AS (amine equivalent 450), X-22-161A (amine equivalent 840), X-22-161B (amine equivalent 1500) ( Examples thereof include Shin-Etsu Chemical Co., Ltd., BY16-853 (amine equivalent 650), BY16-853B (amine equivalent 2200), and the like (manufactured by Toray Dow Corning Silicone Co., Ltd.). Moreover, as siloxane diamine represented by the said General formula (6), X-22-9409 (amine equivalent 700), X-22-1660B-3 (amine equivalent 2200) (above, Shin-Etsu Chemical Co., Ltd. product) Etc. can be illustrated.

  In the production of a siloxane-modified polyamideimide, a part of the aromatic diamine may be replaced with an aliphatic diamine as a diamine component. Examples of the aliphatic diamine include a compound represented by the following general formula (7).

In the formula, X represents a methylene group, a sulfonyl group, an ether group, a carbonyl group or a single bond, R ¹ and R ² each independently represent a hydrogen atom, an alkyl group, a phenyl group or a substituted phenyl group, and p is 1 It is an integer of ~ 50. Especially, as R < ¹ > and R < ² >, a hydrogen atom, a C1-C3 alkyl group, a phenyl group, and a substituted phenyl group are preferable. Examples of the substituent which may be bonded to the substituted phenyl group include an alkyl group having 1 to 3 carbon atoms and a halogen atom.

  As the aliphatic diamine, those in which X in the general formula (7) is an ether group are particularly preferable from the viewpoint of achieving both low elastic modulus and high Tg. Examples of such aliphatic diamines include Jeffamine D-400 (amine equivalent 400) and Jeffamine D-2000 (amine equivalent 1000).

  Further, the siloxane-modified polyamideimide is obtained by reacting diimide dicarboxylic acid obtained by reacting the above-described mixture containing siloxane diamine and aromatic diamine (preferably partly aliphatic diamine) with trimellitic anhydride and diisocyanate. To obtain. Examples of the diisocyanate used in such a reaction include compounds represented by the following general formula (8).

In the formula, D is a divalent organic group or divalent aliphatic hydrocarbon group having at least one aromatic ring. For _{example, -C 6 H 4 -CH 2 -C} 6 H 4 - selected from the group consisting of a group represented by tolylene group, a naphthylene group, a hexamethylene group, 2,2,4-trimethylhexamethylene group and isophorone group Preferably, at least one group is selected.

  Thus, examples of the diisocyanate include both an aromatic diisocyanate in which D is an organic group having an aromatic ring and an aliphatic diisocyanate in which D is an aliphatic hydrocarbon group. Among these, as the diisocyanate, an aromatic diisocyanate is preferable, and it is more preferable to use both in combination.

  Examples of aromatic diisocyanates include 4,4′-diphenylmethane diisocyanate (MDI), 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, naphthalene-1,5-diisocyanate, 2,4-tolylene dimer, and the like. It can be illustrated. Of these, MDI is preferable. By using MDI as the aromatic diisocyanate, the flexibility of the resulting polyamideimide can be improved.

  Examples of the aliphatic diisocyanate include hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and isophorone diisocyanate.

  As described above, when the aromatic diisocyanate and the aliphatic diisocyanate are used in combination, the aliphatic diisocyanate is preferably added in an amount of about 5 to 10 mol% with respect to the aromatic diisocyanate. By using together in this way, the heat resistance of polyamideimide tends to be further improved.

  As the thermosetting resin contained in the thermosetting resin composition used for the substrate 1, an acrylic resin can be used in addition to the above-described resin having a glycidyl group and a resin having an amide group. Examples of the acrylic resin include a polymer such as an acrylic monomer, a methacrylic acid monomer, acrylonitrile, an acrylic monomer having a glycidyl group, and a copolymer obtained by copolymerizing a plurality of these monomers. Although the molecular weight of an acrylic resin is not specifically limited, It is a weight average molecular weight of standard polystyrene conversion, Preferably it is 300,000-1 million, More preferably, it is 400,000-800,000.

  The thermosetting resin composition of the substrate 1 may further contain a flame retardant in addition to the resin component described above. By including the flame retardant, the flame retardancy of the substrate 1 is improved. For example, a filler containing phosphorus is preferable as the additive-type flame retardant. As the phosphorus-containing filler, OP930 (trade name, manufactured by Clariant, phosphorus content 23.5% by weight), HCA-HQ (trade name, manufactured by Sanko Co., Ltd., phosphorus content 9.6% by weight), melamine polyphosphate PMP- 100 (Phosphorus content 13.8% by weight) PMP-200 (Phosphorus content 9.3% by weight) PMP-300 (Phosphorus content 9.8% by weight, trade name manufactured by Nissan Chemical Co., Ltd.) .

  In the printed wiring board 40, the conductors 7, 8 and 9 are formed from the copper foils 2 and 3 of the copper-clad laminate 30 used for manufacturing the printed wiring board 40. As a material for the conductors 7, 8 and 9, aluminum foil is generally used in addition to the copper foil mentioned in the above example. However, if it is a metal foil having a thickness of about 5 to 200 μm usually used for a metal-clad laminate or the like. There is no particular limitation. In addition to a single metal foil, nickel, nickel-phosphorus, nickel-tin alloy, nickel-iron alloy, lead, lead-tin alloy, etc. are used as intermediate layers, and a copper layer of 0.5 to 15 μm and 10 A composite foil having a three-layer structure in which a copper layer of ˜300 μm is provided, or a composite foil having a two-layer structure in which aluminum and a copper foil are combined may be used.

  The metal-clad laminates such as the copper-clad laminate 30 used for the production of the insulating plate, the laminate, and the printed wiring board 40 constituting the substrate 1 can be manufactured as follows, for example. That is, first, a fiber base material is impregnated with the above-described thermosetting resin composition, and a prepreg obtained by semi-curing the thermosetting resin composition is prepared. Next, metal foil such as copper foils 2 and 3 is stacked on one side or both sides of the prepreg or a laminate obtained by laminating a plurality of the prepregs. The obtained laminate is preferably heated and pressed at a temperature in the range of 150 to 280 ° C., more preferably in the range of 180 ° C. to 250 ° C., preferably 0.5 to 20 MPa, more preferably 1 to 8 MPa. Mold. Thereby, the insulating board or laminated body applicable to the base material 1 is obtained from the prepreg mentioned above or its laminated body, and the copper-clad laminated board 30 (copper foil 2 and 3 laminated | stacked on both surfaces of this base material 1 ( A metal-clad laminate) is obtained.

  As mentioned above, although the structure of the suitable printed wiring board was demonstrated, the printed wiring board of this invention is not restricted to the thing of a single layer as mentioned above, It is a multilayer wiring board which laminated | stacked the single-layer printed wiring board. Also good. For example, the multilayer wiring board which laminated | stacked the prepreg as mentioned above between the printed wiring board produced separately, copper foil, etc., and also processed so that copper foil might become an outer layer circuit is mentioned. In this multilayer wiring board, the interlayer connection between the inner layer circuit (conductor in the printed wiring board) and the outer layer circuit is not particularly limited. For example, a hole for interlayer connection is provided in the prepreg with a laser or the like, and plating is performed on this. Examples thereof include a method of filling a conductive paste and a method of using connection bumps provided in advance on an inner layer circuit.

  Moreover, as a multilayer wiring board, what laminated | stacked the prepreg mentioned above on both sides of the several printed wiring board produced separately is mentioned. In this case, as a method of interlayer connection between the circuits (conductors of the printed wiring board) of each layer, for example, a method of filling the prepreg with a conductive paste in a hole for interlayer connection provided in advance by a laser or the like, And a method using connection bumps provided in advance.

  In these multilayer wiring boards as well, the total thickness of the conductors formed in the bent region is 1 to 30 μm and the total thickness of the conductors formed in the non-bent region is 30 to 150 μm, similarly to the printed wiring board as described above. By doing so, it is easy to bend in the bent region, and the rigidity of the non-bent region is kept good. As a result, this multilayer wiring board can also be stored in the electronic device with high density by bending. In addition, as a multilayer wiring board, the same number of printed wiring boards do not need to be laminated | stacked over all the area | regions. For example, in order to ensure that the total thickness of the conductor in the bent region is within the range of 1 to 30 μm, the bent region may be a single layer and only the non-bent region may be multilayered.

  EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to these Examples.

Example 1
First, an imide-based prepreg (manufactured by Hitachi Chemical Co., Ltd.) having a thickness of 50 μm including a glass cloth having a thickness of 0.019 mm (1027 manufactured by Asahi Sebel Co., Ltd.) was prepared. Next, a copper foil (F2-WS-18, manufactured by Furukawa Circuit Foil Co., Ltd.) having a thickness of 18 μm is provided on one side of the prepreg, and a copper foil (SLP-70 Nippon Electrolysis Co., Ltd.) having a thickness of 70 μm is provided on the opposite side. Manufactured by Co., Ltd.) were stacked such that the adhesive surfaces were combined with the prepreg. And this was pressed on the press conditions of 230 degreeC and 90 minutes and 4.0 Mpa, and thereby the double-sided copper clad laminated board was obtained.

  MIT-225 (manufactured by Nippon Synthetic Morton Co., Ltd., thickness 25 μm) was laminated as an etching resist on both sides of this double-sided copper-clad laminate, and processed into a predetermined pattern by a conventional photolithography process. Then, the copper foil was etched with a ferric chloride-based copper etching solution. This etching was completed when pattern formation by etching on the side of the 18 μm copper foil was completed, followed by washing with water and drying.

  Then, after further laminating MIT-235 on both sides of the substrate, the entire surface is exposed on one side (18 μm copper foil side), and only the portion that needs to be bent is opened on the other side (70 μm copper foil side). Thus, each resist pattern was formed. Then, the copper foil (remaining copper) portion exposed in the opening portion was etched, and etching was performed until there was no copper in this portion (the portion requiring bending).

  Then, after the etching was completed, a double-sided printed wiring board was obtained by removing all of the etching resist. Thus, the conductor (circuit) having a thickness of 18 μm is provided in the bent region (flexible portion), the above circuit in the non-bent region (rigid portion), and a conductor (solid copper) having a thickness of 70 μm formed on the opposite surface. A printed wiring board having was obtained.

(Example 2)
First, an acrylic epoxy prepreg (manufactured by Hitachi Chemical Co., Ltd.) having a thickness of 50 μm including a glass cloth having a thickness of 0.028 mm (1037 manufactured by Asahi Sebel Co., Ltd.) was prepared. Next, a copper foil having a thickness of 3 μm (Microshin, manufactured by Mitsui Kinzoku Co., Ltd.) was laminated on both sides of the prepreg so that the adhesive surface was combined with the prepreg. And this was pressed on the press conditions of 180 degreeC and 90 minutes and 4.0 Mpa, and thereby the double-sided copper clad laminated board was obtained.

  MIT-235 (manufactured by Nippon Synthetic Morton Co., Ltd., thickness 35 μm) was laminated as a plating resist on both sides of this double-sided copper-clad laminate, and processed into a predetermined pattern by a conventional photolithography process. Then, 16 μm copper was plated on both sides by copper sulfate electroplating.

  Then, after further laminating MIT-235 on both sides of the double-sided copper-clad laminate after plating, one side is exposed entirely, and the other side is opened with a portion that does not require bending (solid pattern portion). Thus, each resist pattern was formed. Subsequently, electroplating was further performed on the plated copper exposed in the opening, so that the conductor thickness of this portion (portion that does not require bending) was 70 μm.

  After completion of the plating, all plating resists were removed, and a copper foil having a thickness of 3 μm was etched with a sulfuric acid / hydrogen peroxide-based etching solution to form a conductor pattern, whereby a double-sided printed wiring board was obtained. . Thus, a conductor (circuit) having a thickness of 18 μm is provided in the bent region (flexible portion), a conductor (circuit) of 18 μm is provided on one side in the non-bent region (rigid portion), and the surface on the opposite side is also 70 μm. A printed wiring board having a conductor (solid copper) was obtained.

(Comparative Example 1)
First, an imide-based prepreg (manufactured by Hitachi Chemical Co., Ltd.) having a thickness of 50 μm including a glass cloth having a thickness of 0.019 mm (1027 manufactured by Asahi Sebel Co., Ltd.) was prepared. Subsequently, a copper foil (GTS-35, manufactured by Furukawa Circuit Foil Co., Ltd.) having a thickness of 35 μm was stacked on both sides of the prepreg so that the adhesive surface was aligned with the prepreg. And this was pressed on the press conditions of 230 degreeC and 90 minutes and 4.0 Mpa, and thereby the double-sided copper clad laminated board was produced.

  MIT-225 (manufactured by Nippon Synthetic Morton Co., Ltd., thickness 25 μm) is laminated as an etching resist on both sides of this double-sided copper-clad laminate, and one side becomes a predetermined pattern by the conventional photolithography process, and the other side Was processed so as to have a pattern covering the entire surface except the bent portion.

  Then, the copper foil was etched with a ferric chloride-based copper etching solution. This etching was completed when the 35 μm copper foil on the surface having the resist on which the predetermined pattern was formed and the opposite surface exposing the bent portion could be removed, and then washed with water and dried.

  Then, after the etching was completed, a double-sided printed wiring board was obtained by removing all of the etching resist. In this way, the 35 μm conductor (circuit) is provided in the bent region (flexible portion), and the 35 μm circuit (solid copper) formed on the opposite surface is provided in the non-bent region (rigid portion). A printed wiring board having a conductor having a thickness of 70 μm was obtained.

(Bending test)
The printed wiring boards obtained in Examples 1 and 2 were each subjected to a bending test. As a result, both printed wiring boards could be arbitrarily bent at the flexible part. Specifically, it was possible to bend 180 degrees along a pin having a radius of curvature of 0.5 mm. When the folded wiring board was opened again, no abnormalities such as cracks were found in the bent portion.

  On the other hand, after bending the bent portion of the printed wiring board of Comparative Example 1 180 degrees along a pin having a curvature radius of 0.5 mm in the same manner as described above, when the bent portion is opened, the bent portion is whitened and the base material It was confirmed that there was a crack between the copper foils.

DESCRIPTION OF SYMBOLS 1 ... Base material, 2, 3 ... Copper foil, 4 ... Etching resist pattern, 5 ... Etching resist, 6 ... Part which should become a bending area, 7, 8, 9 ... Conductor, 10 ... Copper foil, 17, 18, 19 DESCRIPTION OF SYMBOLS ... Conductor, 20 ... Plating resist pattern, 21 ... Plating copper, 22 ... Part which should become a non-bending area | region, 23 ... Plating copper, 24 ... Plating resist pattern, 30 ... Copper-clad laminate, 36 ... Bending area | region, 40 ... Printing Wiring board, 46 ... non-bending area, 56 ... bending area, 60 ... printed wiring board, 66 ... non-bending area.

Claims (8)

A printed wiring board comprising a base material having flexibility and a conductor formed on at least one side of the base material,
Having a bent region that is bent and a non-bent region that is not bent;
The conductor formed in the bent region has a thickness of 1 to 30 μm, the conductor formed in the non-bent region has a thickness of 30 to 150 μm,
The thickness of the conductor formed in the non-bending region is larger than the thickness of the conductor formed in the bending region,
The printed wiring board, wherein a thickness of the conductor formed in the bent region is 6 to 60% of a thickness of the conductor formed in the non-bent region.   The printed wiring board according to claim 1, wherein the conductor formed in the bent region has a thickness of 1 to 30 μm by etching.   The printed wiring board according to claim 1, wherein the conductor formed in the non-bending region has a thickness of 30 to 150 μm by plating.   The printed circuit board according to any one of claims 1 to 3, wherein the substrate includes a fiber substrate, and the fiber substrate is a glass cloth having a thickness of 50 µm or less.   The printed wiring board as described in any one of Claims 1-4 with which the said base material contains a thermosetting resin composition.   The printed wiring board according to claim 5, wherein the thermosetting resin composition includes a resin having a glycidyl group.   The printed wiring board according to claim 5 or 6, wherein the thermosetting resin composition contains a resin having an amide group.   The printed wiring board according to claim 5, wherein the thermosetting resin composition includes an acrylic resin.

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