JP5556986B2 - Multi-wire wiring board adhesive, multi-wire wiring board using this adhesive, and manufacturing method thereof - Google Patents

Description

  The present invention relates to an adhesive used for a multi-wire wiring board, a multi-wire wiring board using the adhesive, and a manufacturing method thereof.

  A multi-wire wiring board that provides an adhesive layer on a substrate, lays and fixes an insulation-coated wire (hereinafter abbreviated as “wire” unless otherwise specified) for forming a conductor circuit, and connects the layers by through holes is patented. It is disclosed by Literature 1, Patent Literature 2, Patent Literature 3, and Patent Literature 4, and is known as a printed wiring board that can form high-density wiring and is advantageous for matching characteristic impedance and reducing crosstalk.

  In the patent document, as a manufacturing process of a multi-wire wiring board using an adhesive layer composed of a thermosetting resin, a curing agent, and a rubber component, (1) production of an inner layer circuit board, (2) on an inner layer circuit board It is described that laminating adhesive, (3) fixing insulated wires with a numerically controlled automatic wiring machine, (4) laminating prepreg, (5) drilling through holes, and (6) copper plating of through holes. Has been. The reason why the prepreg is used in the step (4) is to prevent the wire from being peeled when drilling with a drill or the like, or to prevent the reliability of the wire from being damaged due to damage in the subsequent plating step. Because.

  In addition, the reason for using a rubber component for the adhesive is that the adhesive is applied to the support film and dried to produce an adhesive sheet, which is laminated and bonded onto an insulating substrate or an inner circuit board laminated with a prepreg. Because it is used, it is necessary to be able to form an adhesive layer, to have flexibility, and to be non-adhesive except when wiring, in order to facilitate handling in work. It is. Furthermore, when fixing the wire to the adhesive layer, the wire is brought into contact with the adhesive layer at the tip while the stylus vibrates with ultrasonic waves, and the adhesive layer is activated and melt bonded by the thermal energy generated by the ultrasonic vibration. Therefore, it is necessary to have a meltable composition.

  Printed wiring boards including multi-wire wiring boards have been advanced in high density and miniaturization in order to support high density mounting. When this high density and miniaturization is performed with a multi-wire circuit board, the insulation resistance between the wires, the insulation resistance between the wires and the inner circuit layer, and the positional accuracy of the wires are extremely important. It is necessary to keep the insulation resistance between the conductors high and to prevent the wires from moving in the process of wiring or after wiring. In the conventional technique, the insulation resistance falls within an allowable error at the conventional wiring density, and the wire position accuracy is about 0. 0 with respect to the design value after the wiring is performed and the printed wiring board is laminated and bonded. Although there was a movement of about 2 mm (hereinafter referred to as wire swimming), the wiring density was low and the hole diameter was large.

  However, as described above, when the wiring density increases, the insulation resistance decreases with the adhesive using the rubber component. In addition, as the hole density increases, the hole diameter also decreases, and when wire swimming is large, the wire at the position to be a through hole moves, causing a problem of connection failure without being connected. The cause of this decrease in insulation resistance and increased wire swimming was the use of a rubber component in the adhesive. That is, since the insulation resistance of the rubber component itself is low and the prepreg and the like are laminated and bonded while the flow of the rubber component in the adhesive remains after wiring, wire swimming occurs.

  Therefore, as disclosed in Patent Document 5, a UV curable adhesive sheet having an epoxy resin, an epoxy-modified polybutadiene, a cationic photopolymerization initiator, and the like as an adhesive has been developed. Since this adhesive is laminated after the wiring is slightly cured with ultraviolet rays after the wiring, wire swimming can be suppressed, and an epoxy-modified polybutadiene component having a high insulation resistance is used instead of the rubber component of the adhesive. By introducing it, the decrease in insulation resistance is suppressed.

  In recent years, multi-wire wiring boards have been increasing in number of layers in order to cope with higher density mounting. However, the multi-wire wiring board using the adhesive disclosed in Patent Document 5 has a problem that the heat resistance of the solder is lowered with the increase in the number of adhesive layers to which the wires are fixed. This is because, in the multi-wire circuit board, the glass transition point is low and the occupancy ratio of the adhesive having a large thermal expansion coefficient equal to or higher than the glass transition point is increased. It is described that peeling occurs, and the characteristics of the adhesive are greatly involved. That is, at that time, it was thought that the heat resistance was improved by reducing the difference between the thermal expansion coefficient and the elastic modulus of the base material (substrate) or the prepreg and the adhesive less than Tg and more than Tg. For this reason, it has been considered essential to improve the elastic modulus below Tg and above Tg and reduce the coefficient of thermal expansion.

  Thereafter, studies were made to improve heat resistance, and the multi-wire wiring board using the adhesive disclosed in Patent Document 6 was able to withstand the heat resistance test of a solder float at 288 ° C. This adhesive is composed of a polyamideimide resin having a molecular weight of 80,000 or more and a thermosetting component. The cured product has a glass transition temperature (hereinafter abbreviated as Tg) of 180 ° C. or higher, and a thermal expansion coefficient from Tg to 350 ° C. of 1000 ppm. Below, the minimum elastic modulus at 300 ° C. is defined by the physical properties of 30 MPa or more.

U.S. Pat. No. 4,097,684 US Pat. No. 3,646,572 US Pat. No. 3,674,914 US Pat. No. 3,674,602 Japanese Patent No. 3324007 Japanese Patent No. 3812252

  However, in order to meet the recent demand for higher multi-layers, it has become necessary to make the base material (substrate) thinner. Conventionally, the substrate thickness was 0.2 mm or more, but recently, 0.1 mm or less has begun to be used. In general, when a wire is laid, a prepreg is press-laminated on both surfaces of a substrate (substrate) on which a circuit is formed, and an adhesive is stuck on the prepreg. The ultrasonic vibration mechanically transmitted via the wire thermally melts the adhesive that is easily deformed, but by reducing the thickness of the plate, the mass per unit area of the substrate directly below it becomes small, and the substrate Becomes easy to follow the ultrasonic vibration, the heat generation efficiency due to the ultrasonic wave in the above adhesive is reduced, and the problem arises that the wiring property is lowered. Specifically, even if the wires are wired under the same wiring conditions, the wires cannot be sufficiently fixed to the adhesive at the high density portion, and disconnection or short-circuit failure due to misalignment of the wires occurs. For this reason, with the adhesive described in Patent Document 6 (Japanese Patent No. 3812252), it has become difficult to produce multi-wires using a base material (substrate) thinner than 0.2 mm.

  In addition, what must be considered in the adhesive is that a rubber component with low insulation resistance should not be added in order to suppress a decrease in insulation resistance, that the position accuracy of the wire must be improved, prepreg, base material (substrate) ), Glass transition point for reducing the thermal expansion coefficient of the adhesive: use a material having a high Tg, flexibility to make the conventional manufacturing apparatus and manufacturing method usable as much as possible, film formation And non-adhesiveness other than during wiring can be maintained.

  INDUSTRIAL APPLICABILITY The present invention is excellent in various properties, can wire a base material (substrate) thinner than 0.2 mm, and can suppress a decrease in solder heat resistance due to the increase in the number of layers and an adhesive for a multi-wire wiring board A multi-wire wiring board using an agent and a method for producing the same are provided.

The present invention is as follows.
The adhesive for multi-wire wiring board of the present invention comprises (a) a polyamideimide resin having a weight average molecular weight of 80,000 or more, and (b) a polyamideimide resin having a weight average molecular weight in the range of 10,000 to 50,000. (C) It is an adhesive agent containing a thermosetting component, Comprising: The glass transition point (Tg) of hardened | cured material is 180 degreeC or more.
In the adhesive for a multi-wire wiring board, the mass ratio of (a) :( b) is in the range of 30:70 to 70:30, and the mass ratio of (a) + (b) :( c) Is preferably in the range of 100: 10 to 100: 150.
In the multi-wire wiring board adhesive, it is preferable that the end of the polyamide-imide resin (b) is an isocyanate group, and the isocyanate group is bonded to a mask agent that is dissociated by heating.
In the multi-wire wiring board adhesive, the thermosetting component (c) includes one or more types of epoxy resins, and includes a curing agent for the epoxy resin or a curing accelerator for the epoxy resin. Is preferred.
In the multi-wire wiring board adhesive, at least one of the epoxy resins is preferably liquid at room temperature (25 ° C.).
In addition, the multi-wire wiring board of the present invention is provided at a desired location with an insulating substrate or a substrate on which a conductor circuit has been previously formed, an adhesive layer made of the adhesive, an insulating coated wire fixed by the adhesive layer, and the like. It consists of a through hole.
Furthermore, the manufacturing method of the multi-wire wiring board of the present invention includes a step of forming an adhesive layer made of the above-mentioned adhesive on an insulating substrate or a substrate on which a conductor circuit has been previously formed, and wiring the insulating coated wire on the adhesive layer. And fixing the adhesive layer by heating and pressing the substrate, and forming a conductor circuit by forming a hole in a desired portion of the substrate and plating the inner wall of the hole. It is characterized by.
Moreover, in the manufacturing method of the said multi-wire wiring board, after heat-pressing the said board | substrate, it is preferable to heat-process further.

  ADVANTAGE OF THE INVENTION By this invention, the adhesive for multi-wire wiring boards which can be wired with respect to the base material (board | substrate) which is excellent in various characteristics and thinner than 0.2 mm, and can suppress the fall of the solder heat resistance by multi-layering, and this adhesion | attachment It has become possible to provide a multi-wire wiring board using an agent and a method for producing the same.

(A)-(h) is sectional drawing of each manufacturing process which shows one Example of this invention.

  The adhesive used in the present invention is used as an insulating layer for fixing an insulating coated wire (hereinafter abbreviated as a wire) used for a multi-wire wiring board with an apparatus called a wiring machine. This adhesive is a varnish prepared by dissolving various components in a solvent, and may be applied directly on the substrate and dried, but preferably coated on a film using a coating machine on a peelable carrier film, A method of drying and forming a B-stage film having a uniform film thickness and bonding it to a substrate with a hot roll laminator or the like is preferable. For this reason, the component of the adhesive contains a polyamideimide resin component having a large molecular weight. The substrate is also referred to as a substrate or an insulating substrate.

  In the present invention, (a) a polyamideimide resin having a weight average molecular weight of 80,000 or more is used. If the adhesive for a multi-wire wiring board of the present invention does not contain a polyamideimide resin having a weight average molecular weight of 80,000 or more, the film formability at the B stage, the wiring property (fixing force) of the wire, and the wire in the process Position accuracy may be reduced. The weight average molecular weight of the (a) polyamideimide resin is preferably 200,000 or less from the viewpoint of availability.

  Next, in the adhesive for multi-wire wiring boards of the present invention, (b) a polyamideimide resin having a weight average molecular weight in the range of 10,000 to 50,000 is used. The (b) polyamideimide resin preferably has a similar skeleton to the (a) polyamideimide resin. When blending the varnish of the adhesive for a multi-wire wiring board, if the skeleton of the polyamideimide resin is different, the compatibility is low and phase separation is easy. The reason why the weight average molecular weight is defined in the range (b) and the reason for using it together with (a) is that, as a result of intensive studies, it has been found that the wiring property can be improved as compared with the case of (a) alone. is there. If the weight average molecular weight of (b) is outside this range, the effect of improving the wiring property may be reduced.

  In the present invention, the mass ratio of (a) :( b) is preferably in the range of 30:70 to 70:30. When the mass ratio of the component (a) is greater than 70, the component having a low molecular weight is decreased, so that the embedding property of the wire is not improved, and a wiring failure may occur in a substrate thinner than 0.2 mm. is there. On the other hand, when the mass ratio of the component (a) is less than 30, the component having a high molecular weight is reduced, so that cracks may occur during film formation, and the holding power of the wire may be reduced. In the present invention, (c) a thermosetting component is used. With only the thermoplastic polyamideimide resin component, wet processing during the manufacturing process of the wiring board, for example, forming through-holes after drilling, dissolution, deterioration due to roughening, chemical treatment of plating, deterioration of the characteristics of the wiring board May cause. Furthermore, in solder reflow for component mounting, thermal expansion is large and heat resistance is lowered, and the inside of the board may flow. For this reason, it is necessary to bridge | crosslink an adhesive agent with a thermosetting component, to suppress a thermal expansion coefficient, and to suppress the resin flow at high temperature. Therefore, the mass ratio of (a) + (b) :( c) is preferably in the range of 100: 10 to 100: 150. When the mass ratio of the component (c) is less than 10, since there are few thermosetting components, there is a risk of poor wiring due to insufficient adhesion. Moreover, when there are many (c) components exceeding 150, it will gelatinize at the time of a varnish compounding from a compatible fall, and there exists a possibility that film formation cannot be performed.

  Moreover, the glass transition point (Tg) of the hardened | cured material of the adhesive agent of this invention is 180 degreeC or more. The adhesive of the present invention usually becomes a cured product under conditions of 180 to 220 ° C. and 0.5 to 2 hours. The cured product refers to a state in which the heat of reaction is measured by a differential scanning calorimeter (DSC) and the heat generation amount is 10% or less with respect to the heat generation amount of the raw material (adhesive). In general, when the organic substance exceeds Tg, the coefficient of thermal expansion increases by about 10 times, and as a result, the thermal expansion during reflow is too large, resulting in a decrease in heat resistance. This can be suppressed to some extent by the addition of a thermosetting component, but if the Tg as a cured product is less than 180 ° C., the heat resistance may decrease.

  The reason why the polyamide-imide resin is used for the components (a) and (b) of the present invention is that the synthesis of a polyamide-imide resin having a high Tg is easy, and the amide bond portion in the skeleton is inserted with an epoxy resin described later. However, it can be used as a crosslinking point. As the skeleton of the polyamide-imide resin, those having aromaticity are preferable in order to obtain Tg of 180 ° C. or higher after curing. Further, although there are various synthetic methods, an isocyanate method in which the skeleton is easily controlled and no ionic impurities are mixed to reduce the insulating property is preferable. As an example, an aromatic polyamideimide having a weight average molecular weight of 10,000 or more can be synthesized by subjecting a raw material to an equivalent reaction of a diimide dicarboxylic acid obtained by subjecting an aromatic diamine and trimellitic anhydride to an equivalent reaction and an aromatic diisocyanate. By precisely controlling the equivalent ratio, the weight average molecular weight can be increased to 80,000 or more, and further to 100,000 or more. The terminal of the polyamideimide resin synthesized by this method is generally an amide group or a carboxyl group, and in the latter case, it can be reacted with an epoxy resin under a basic catalyst.

  Examples of the aromatic diimide dicarboxylic acid as a base of the polyamideimide resin include those represented by the following formula 1. In addition, examples of the aromatic diisocyanate include those represented by the following formula 2. The weight average molecular weight of the synthesized polyamideimide resin is measured using gel permeation chromatography (GPC). A molecular weight / elution time curve is prepared with standard polystyrene, and the weight average molecular weight is determined by converting the resin from the elution time to polystyrene. As the measurement conditions, column GL-S300MDT-5 (trade name, manufactured by Hitachi High-Technologies Corporation) is used, and a mixed solvent of dimethylformamide (DMF) / tetrahydrofuran (THF) is used as a solvent.

  In the present invention, it is preferable that the end of the polyamideimide resin (b) is an isocyanate group, and the isocyanate group is bonded to a masking agent that is dissociated by heating. Although it is relatively stable against heat by bonding a masking agent, it can be used as a crosslinking point by heating at 100 ° C. or higher, and is effective in improving Tg, fluidity control, and wiring. This mask isocyanate group can be cross-linked with other functional groups such as an epoxy resin skeleton or a hydroxyl group generated after the reaction. In addition, as a method for improving the wiring property of the wire, it has been found by the inventor's long-term research that it is preferable that the polyamideimide component has a slight cross-linked structure as the film physical property of the B stage. In this respect, this mask isocyanate group is suitable, and can be reacted slightly by controlling the heating at the time of drying at the time of film-forming coating. Furthermore, it is effective in reducing the coefficient of thermal expansion of the cured product by finally heat-curing. Various methods of introducing an isocyanate group into (b) are conceivable, but the method of making the diisocyanate excessive by the isocyanate method exemplified above is simple. Furthermore, it is obtained by reacting various masking agents after synthesizing this isocyanate-terminated polyamideimide resin. The masking agent may be a compound having active hydrogen, such as MEK oxime, malonic acid diester, acetoacetate ester, ε-caprolactam, phenol, alcohol, etc. In the present invention, MEK oxime is suitable. . Although the thermal reactivity is lower than that of a free isocyanate group, the stability at room temperature (25 ° C.) is good, which is sufficient for the storage stability of the adhesive.

  In the present invention, it is preferable that the thermosetting component (c) contains one or more epoxy resins and a curing agent or curing accelerator thereof. The glycidyl group of the epoxy resin reacts with the epoxy resins depending on the curing agent or curing accelerator, but can be crosslinked by an insertion reaction with the amide group of the polyamideimide resin as described above. Thereby, Tg of hardened | cured material shall be 180 degreeC or more, and heat resistance can be improved by suppressing thermal expansion.

  Furthermore, a plurality of epoxy resins can be used. In this case, it is preferable that at least one is liquid at room temperature (25 ° C., the same applies hereinafter). In order to secure the wiring property of the wire with the B stage film, it is preferable that a liquid is included at room temperature, and by making the film flexible at room temperature, the ultrasonic vibration applied to the wire at the time of wiring is added to the adhesive. It is transmitted and easily converted into heat energy, and the wire is easily embedded in the adhesive. For example, although a solvent is contained in this, the shrinkage | contraction at the time of removing by the heating in a process becomes large. The liquid epoxy resin has the effect of reducing the amount of solvent and also has the effect of reducing this heat shrinkage.

  Any epoxy resin can be used as long as it has two or more glycidyl groups, and more preferably three or more glycidyl groups. Examples of liquid epoxy resins at room temperature include bisphenol A type YD128, YD8125 (trade name, manufactured by Toto Kasei Co., Ltd.), Ep815, Ep828 (trade name, manufactured by Yuka Shell Epoxy Co., Ltd.), DER337 (Dow Chemical Japan Co., Ltd.) Product name), bisphenol F type YDF170, YDF2004 (manufactured by Toto Kasei Co., Ltd., trade name).

  Moreover, as an epoxy resin solid at room temperature, YD907, YDCN704S, YDPN172, YP50 (product name made by Toto Kasei Co., Ltd.), Ep1001, Ep1010, Ep180S70 (product name made by Yuka Shell Epoxy Co., Ltd.), ESA019, ESCN195 (Trade name) manufactured by Sumitomo Chemical Co., Ltd., DER667, DEN438 (trade name, manufactured by Dow Chemical Japan Co., Ltd.), EOCN1020 (trade name, manufactured by Nippon Kayaku Co., Ltd.). Further, in order to impart flame retardancy, a brominated epoxy resin may be used. For example, YDB400 (Toto Kasei Co., Ltd., trade name), Ep5050 (Oka Shell Epoxy Co., Ltd., trade name), ESB400 ( Sumitomo Chemical Co., Ltd., trade name). Moreover, although these may be used independently, you may select a some epoxy resin as needed.

  As the curing agent or curing accelerator for the epoxy resin, amines, imidazoles, polyfunctional phenols, acid anhydrides and the like can be used. Examples of amines include dicyandiamide, diaminodiphenylmethane, and guanylurea. Examples of imidazoles include alkyl-substituted imidazole and benzimidazole. Examples of polyfunctional phenols include hydroquinone, resorcinol, bisphenol A, and halogen compounds thereof. These include novolaks and resol resins that are condensates with aldehydes, and examples of acid anhydrides include phthalic anhydride, hexahydrophthalic anhydride, and benzophenone tetracarboxylic acid.

  In addition, as a hardening | curing agent of a commercially available epoxy resin, H-400 (phenol novolak resin, hydroxyl group equivalent 106g / equivalent, the product made by Meiwa Kasei Co., Ltd., brand name), the product made by DIC Corporation, a brand name: Phenolite LF2882, Phenolite Examples include LF2822, Phenolite TD-2090, Phenolite TD-2149, Phenolite VH-4150, Phenolite VH4170, Phenolite KA-1160, Phenolite KA-1163, Phenolite KA-1165, and the like. Moreover, as a hardening accelerator of a commercially available epoxy resin, 2E4MZ, 2PZ-CN, 2PZ-CNS (above, the Shikoku Kasei Kogyo Co., Ltd. make, brand name) etc. are mentioned.

  In the case of amines, the compounding amount of these curing agents is preferably such that the equivalent of the active hydrogen of the amine and the epoxy equivalent of the epoxy resin are substantially equal. For example, in the case of a primary amine, there are two hydrogens, and for 1 equivalent of epoxy resin, this primary amine is 0.5 equivalent, and in the case of secondary amine, it is 1 equivalent. Next, in the case of imidazoles, it is not simply an equivalent ratio with active hydrogen, and is preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the epoxy resin. In the case of polyfunctional phenols and acid anhydrides, 0.8 to 1.2 equivalents are preferable with respect to 1 equivalent of epoxy resin.

In the adhesive for a multi-wire wiring board of the present invention, an electroless plating catalyst is used in order to increase the plating adhesion of the through-hole inner wall and the like as required, and to manufacture the wiring board by an additive method. It can also be added.
Usually, the said component is mixed in an organic solvent, and it is set as an adhesive varnish. Any organic solvent may be used as long as it has good solubility. For example, when a polyamideimide resin suitable for the present invention is used, dimethylacetamide, dimethylformamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, γ-butyrolactone, sulfolane, cyclohexanone and the like can be exemplified. The resin solid content in the adhesive varnish is usually 20 to 40% by mass.

The manufacturing method of the multi-wire wiring board using the adhesive agent of this invention is demonstrated using FIG.
First, FIG. 1A shows a substrate 1 on which conductor circuits (inner layer copper circuits) such as a power source and a ground are provided in advance. The conductor circuit can be formed of a glass cloth epoxy resin copper clad laminate, a glass cloth polyimide resin copper clad laminate or the like by a known etching method or the like. If necessary, the inner layer copper circuit 2 can be a multilayer circuit or can be completely eliminated. Therefore, an insulating substrate without a conductor circuit may be used.

  FIG. 1B is a diagram in which an insulating layer is formed as the underlay layer 3. This is provided in order to improve the electric corrosion resistance and adjust the characteristic impedance, but it may not always be necessary. For this underlay layer 3, a B-stage prepreg made of ordinary glass cloth epoxy resin or glass cloth polyimide resin, or a B-stage resin sheet containing no glass cloth can be used. These resin layers are laminated on a substrate and then subjected to heat treatment or curing by lamination as necessary to form an insulating layer (underlay layer).

  Next, as shown in FIG.1 (c), the adhesive layer 4 for wiring and fixing a wire is formed using the said adhesive agent. Examples of the method for providing the adhesive layer 4 include a method in which the adhesive is directly applied to an insulating substrate by spray coating, roll coating, screen printing, or the like, and dried. In order to obtain an adhesive layer with a uniform film thickness, a carrier film such as polypropylene or polyethylene terephthalate is roll-coated, coated and dried to form a dry film (adhesive film), and then hot roll laminated or pressed on an insulating substrate. A method of laminating is preferred. Furthermore, the coating film formed into a dry film needs to be flexible so that it can be rolled into a roll and cut into a desired size, and non-adhesive so as not to entrap bubbles when laminating to a substrate. .

  Next, as shown in FIG.1 (d), the insulation coating wire 5 is wired. This wiring is generally performed by heating while applying ultrasonic vibration or the like with a wiring machine. Thereby, the adhesive layer 4 is softened and embedded in the adhesive layer. However, if the softening point of the adhesive layer 4 is too low, the wire 5 may be peeled off from the adhesive layer 4 at the end of the wire 5, or the wire 5 may be bent at a corner portion where the insulating coating wire 5 is bent at a right angle. May be distorted, and sufficient accuracy may not be obtained.

In addition, if the softening point of the adhesive layer is too high, the wire is not sufficiently embedded during wiring, and the adhesive force between the wire and the adhesive layer is small, so that the wire may be peeled off or When the first wire gets over the lower wire, the lower wire is pushed and misalignment occurs. For this reason, it is necessary to control the softening point of the adhesive layer within an appropriate range during wiring.
Therefore, the softening point of the adhesive layer is preferably 20 to 100 ° C. In the adhesive for a multi-wire wiring board of the present invention, the softening point of the adhesive layer made of the adhesive can be set to 20 to 100 ° C. with the above composition.

  The wires used for the wiring are insulation-coated so as not to be short-circuited even if they are crossed on the same plane. The wire core is made of copper or copper alloy and coated with polyimide or the like. Moreover, in order to improve the adhesive force of the cross | intersection part between a wire and a wire, a wire contact bonding layer can be further provided in the outer side of an insulating coating layer. The wire adhesive layer may be a thermoplastic, thermosetting, or photocuring type material, but preferably has the same composition as the adhesive described below.

  After finishing the wiring, heat pressing is performed. Here, the unevenness of the wired substrate surface is reduced, and voids remaining in the adhesive layer are removed. The voids in the adhesive layer are generated when the wire is wired while ultrasonically heating the wire, or are caused by a space formed near the intersection of the wire and the wire. Smoothing the surface of the substrate and removing voids in the adhesive layer are essential. After this hot pressing, the adhesive layer is completely cured by heat treatment. Also, this heat treatment can be omitted if necessary.

  Next, as shown in FIG.1 (e), the overlay layer 6 for protecting the wired wire is provided. The overlay layer 6 is usually made by applying a B-stage prepreg of glass cloth epoxy resin or glass cloth polyimide resin, or a B-stage resin sheet not containing glass cloth, and finally curing them.

  Next, as shown in FIGS. 1F and 1G, after necessary holes are formed (via holes and through holes), plating is performed. Here, a circuit can be formed on the surface by a known etching method or the like by attaching a metal foil such as a copper foil to the surface via a prepreg when forming an overlay layer before drilling such as a through hole. A multi-wire wiring board having two wiring layers is completed by the manufacturing method as described above.

  Next, as shown in FIG. 1 (h), the completed two-layer wiring multi-wire wiring board is a B-stage prepreg made of glass cloth epoxy resin or glass cloth polyimide resin with two multi-wire wiring boards as insulating layers. Alternatively, they are laminated and bonded via a B-stage resin sheet or the like that does not contain glass cloth. Then, after drilling a required location, it plating. A multi-wire wiring board having four wiring layers is completed by the manufacturing method as described above. Alternatively, a multi-wire wiring board having six or more wiring layers can be formed by laminating and bonding three or more multi-wire wiring boards having two wiring layers via an insulating layer. Moreover, the layer which formed the circuit can also be included between two or more 2 layer wiring multi-wire wiring boards as needed.

(Function)
As described above, the use of a polyamideimide resin having a weight average molecular weight of 80,000 or more in the adhesive of the present invention can improve the handleability of the B-stage adhesive. By using together two types of polyamide-imide resins having a similar skeleton to this polyamide-imide resin and having a weight average molecular weight in the range of 10,000 to 50,000, on the wire adhesive layer and the substrate when wiring at high density The wiring property was improved by maintaining the adhesion between the adhesives of the provided B stage. Moreover, the end of the low molecular weight polyamideimide resin is made to be a highly reactive isocyanate group, and by using a polyamideimide resin obtained by reacting this with a mask agent, and using a liquid epoxy resin, the wiring property is further improved. became. Moreover, the heat resistance at the time of the solder reflow of the multi-wire wiring board using this adhesive agent improves by setting the glass transition point of the hardened | cured material of an adhesive agent to 180 degreeC or more.

  In the multi-wire wiring board of the present invention, an adhesive having the above composition that can be thermoset is applied. In the manufacturing process of a multi-wire wiring board using a normal UV curable adhesive AS-U01 (trade name, manufactured by Hitachi Chemical Co., Ltd.), the wires are wired and then slightly cured by UV treatment. By doing so, wire swimming is suppressed. On the other hand, since the adhesive of the present invention uses a polyamideimide resin having a weight average molecular weight of 80,000 or more, the flow of the resin is small, and even when the hot pressing is performed after the wiring, the wire swimming is almost observed. Therefore, the wire can be fixed by a heating press and the adhesive layer made of an adhesive can be cured.

  Also, according to the present invention, the voids generated in the vicinity of the crossing portion of the air bubbles and wires generated in the adhesive are removed by the temperature, pressure and time of the heating press after the wiring, and the unevenness of the substrate surface is reduced. it can. As a result, it is possible to manufacture a multi-wire wiring board with high connection reliability free from bubbles and voids even after the overlay layer as shown in FIG.

EXAMPLES Next, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.
Examples 1-7 and Comparative Examples 1-6
(Synthesis of polyamide-imide resin)
380 g of 2,2′-bis [4- (4-aminophenoxy) phenyl] propane, 190 g of trimellitic anhydride, and 2600 g of N-methylpyrrolidone are placed in a large four-necked flask and heated to temporarily hold at 80 ° C. Then, toluene is added and refluxed. Thereafter, the temperature is raised to 190 ° C. and cooled to room temperature. Thereafter, 250 g of 4,4′-diphenylmethane diisocyanate (MDI) was added, heated to 170 ° C., held for 2 hours, and cooled to room temperature. The molecular weight in terms of polystyrene of the aromatic polyamideimide synthesized with this varnish was 120,000 in terms of weight average.
When changing the molecular weight, the ratio of MDI was changed. Further, when the isocyanate terminal was used, MDI was excessive. Furthermore, when making a mask agent react with an isocyanate group, MEK oxime was finally added 1.5% with respect to the solid mass of a polyamide-imide resin, and it hold | maintained at 100 degreeC for 1 hour, Then, it cooled to room temperature.
These methods have a weight average molecular weight of about 120,000 (hereinafter abbreviated as PAI-a), a molecular weight of about 70,000 (hereinafter abbreviated as PAI-b), and a weight average molecular weight of about 40,000. A product (hereinafter abbreviated as PAI-d), a product obtained by reacting MEK oxime with an isocyanate group having a weight average molecular weight of about 30,000 and both ends (hereinafter abbreviated as PAI-d) was synthesized.

(Adhesive varnish)
With respect to the synthesized polyamideimide resin, various components were blended in the resin blend shown in Table 1 below to obtain an adhesive varnish. In addition, (c) thermosetting component in Table 1 includes EOCN1020 (trade name, manufactured by Nippon Kayaku Co., Ltd.) as a solid epoxy resin, and bisphenol A type YD8125 (Toto Kasei Co., Ltd.) as a liquid epoxy resin. 2E4MZ (manufactured by Shikoku Kasei Kogyo Co., Ltd.) with H-400 (phenol novolac resin, hydroxyl group equivalent 106 g / equivalent, Meiwa Kasei Co., Ltd., product name) as a curing agent , Product name). Moreover, the organic solvent mix | blended with the varnish for adhesive agents is N-methyl-2-pyrrolidone, and resin solid content is 30 mass%.

(Adhesive film coating)
The adhesive varnish is applied to Tetron film HSL-50 (trade name, manufactured by Teijin Limited), which is a transfer substrate, so that the film thickness after drying is 100 μm, and a B-stage state is obtained. Thus, it dried for 10 minutes at 100 degreeC, and produced the adhesive film. In Comparative Examples 3 to 5, an adhesive film could not be produced due to cracks in the film coating film and in Comparative Example 6 due to gelation of the adhesive varnish.

(Measurement of glass transition point of cured adhesive; TMA method)
The adhesive film was heated at 150 ° C. for 30 minutes and subsequently subjected to heat treatment at 180 ° C. for 120 minutes to be cured to obtain a sample (cured product) for glass transition point measurement. The measurement conditions are as follows. Using TMA manufactured by MAC SCIENCE, measuring with jig: tension, distance between chucks: 15 mm, measurement temperature: room temperature to 350 ° C., heating rate: 10 ° C./min, tensile load: 5 g, sample size: 5 mm width × 30 mm length did. The results are shown in Table 2 below.
In Comparative Examples 3 to 6, an adhesive film could not be produced, and therefore a glass transition point measurement sample (cured product) could not be produced, and therefore the glass transition point could not be measured.

Using the adhesive varnish, a multi-wire wiring board was produced by the following method.
(Substrate with adhesive layer)
As a core substrate, a circuit was formed on a glass cloth polyimide resin double-sided copper-clad laminate MCL-I-671 (trade name, manufactured by Hitachi Chemical Co., Ltd.) having a thickness of 0.1 mm or 0.2 mm by a normal etching method. Next, a glass cloth polyimide resin prepreg GIA-671 (trade name, manufactured by Hitachi Chemical Co., Ltd.) having a finished thickness of 0.05 mm was cured by heating press on both sides of the substrate to form an underlay layer. Subsequently, the said adhesive film was adhere | attached on both surfaces of this board | substrate with the hot roll laminator, and the contact bonding layer was formed.
The hot roll laminator conditions were 130 ° C., 0.3 m / min, and 0.5 MPa so that the softening point of the adhesive layer was 50 ° C. In the measurement of the softening point of the adhesive layer, a part of the substrate laminated with the adhesive layer was cut to obtain a sample for measuring the softening point. The measurement conditions are as follows. Using TMA manufactured by MAC SCIENCE, measurement was performed with jig: penetration, measurement temperature: 0 ° C. to 100 ° C., heating rate: 10 ° C./min, compression load: 5 g, sample size 7 mm square.

(Wiring)
Subsequently, a wire (HPA-0.08, trade name, manufactured by Hitachi Cable, Ltd.) was placed on the surface of the adhesive layer of the substrate with a wiring machine while performing ultrasonic heating. This wire has a copper core wire diameter of 80 μm, a polyimide resin of about 15 μm, and a polyamide-imide resin of 15 μm, to form a B-stage adhesive layer.
The wire wiring state on the surface of the adhesive layer when using a core substrate having a plate thickness of 0.1 mm and 0.2 mm was observed with a microscope. As the wiring property, the wire peeling failure was evaluated as x, and the absence of failure was evaluated as ○. The results are shown in Table 2 below.

(Adhesive layer curing)
Next, it heat-pressed on the conditions of 150 kg, 30 minutes, and 16 kgf / cm < ² > by using a polyethylene sheet as a cushioning material. Subsequently, heat treatment was performed at 180 ° C. for 120 minutes to cure the adhesive layer.
(Surface circuit formation)
Next, glass cloth polyimide resin prepreg GIA-671 (manufactured by Hitachi Chemical Co., Ltd., trade name) was bonded on both sides, and further 18 μm copper foil was adhesively cured on the both surfaces by a hot press.

(Drilling / via hole formation)
Subsequently, holes (through holes and via holes) were made in necessary portions of the substrate. After drilling holes, pre-processing such as hole cleaning, removing smears, etc., dipping in an electroless copper plating solution, plating to a thickness of 30 μm, and then etching one side of the inner circuit To form a multi-wire wiring board having a two-layer wiring structure.
(Four-layer wiring structure multi-wire wiring board production)
The structure which arranged the surface which formed the inner layer circuit only on the one side of the two-layer wiring structure multi-wire wiring board of 2 sheets, and arrange | positioned the glass cloth polyimide resin prepreg GIA-671 (made by Hitachi Chemical Co., Ltd., brand name) between them Then, it was cured by a hot press to form an insulating layer. Next, drilling and through-hole plating were performed, a surface circuit was formed by an etching method, and a four-layer wiring structure multi-wire wiring board was manufactured.

(Solder heat resistance test)
The 4-layer wiring structure multi-wire wiring board was dried at 130 ° C. for 6 hours to remove moisture in the substrate. The substrate was cooled to room temperature so as not to absorb moisture in the desiccator. Immediately after that, the sample was floated in a solder bath at 288 ° C. for 10 seconds, and then taken out and cooled to room temperature. After repeating this operation three times, the state of the substrate was observed with a microscope. In the substrate, no occurrence of voids and peeling was indicated as ◯, and occurrence was indicated as x. The results are shown in Table 2 below.

  In Examples 1-7, as a result of measuring the glass transition point by the TMA method, it was found that the glass transition point (Tg) was 180 ° C. or higher in various formulations (adhesives). Even when the substrate (substrate) thickness was 0.1 mm in the wire wiring process during the production of the multi-wire wiring board using these, wiring (wiring) defects did not occur. Further, even after the solder heat resistance test, no voids or peeling occurred in the multi-wire wiring board, which was good.

In Comparative Example 1, in which the polyamideimide resin (b) is not blended, in the wire wiring process during the production of the multi-wire wiring board, when the core substrate thickness is 0.2 mm, the wiring (wiring) defect is Although it did not occur, when the thickness of the core substrate was 0.1 mm, a defect occurred in which the wires were peeled off during wiring. In the comparative example 2, when the plate thickness of the core substrate was 0.1 mm, a defect that the wire was peeled during the wiring occurred.
In Comparative Examples 3 and 4, there was no abnormality in the state of the adhesive varnish, but cracks occurred in the adhesive coating, and Tg could not be measured.
In Comparative Example 5, there was no abnormality in the state of the adhesive varnish, but since the ratio of the polyamideimide resin (a) was small, the adhesive coating film was cracked. Therefore, in Comparative Example 5, the glass transition point (Tg) could not be measured by the TMA method.
In Comparative Example 6, (c) the thermosetting component is more than 150 parts by mass (155 parts by mass) with respect to 100 parts by mass of the polyamideimide resin ((a) + (b)), and gelation occurs during the varnish production. The film could not be formed. Therefore, in Comparative Example 6, the glass transition point (Tg) could not be measured by the TMA method.
In Comparative Examples 1 and 2 in which the glass transition point (Tg) was confirmed to be 180 ° C. or higher, a wiring failure occurred when the thickness of the core substrate was 0.1 mm. After the solder heat resistance test, no voids or peeling occurred in the multi-wire wiring board, which was good.

  As described above, the multi-wire wiring board having four or more wiring layers manufactured using the adhesive according to the present invention has good wiring characteristics even when the core substrate has a thickness of 0.1 mm. Yes, it does not contain voids in the adhesive layer after wiring and fixing the wire, and even if a heating press after wiring is performed, the wire does not move and high-density wiring is possible. A multi-wire wiring board having four or more wiring layers having excellent heat resistance can be provided.

1. Substrate, 2. 2. inner layer copper circuit; 3. Underlay layer, 4. adhesive layer; 5. Wire (insulating coated wire), 6. overlay layer; Via hole, 8. Plating, 9. Interlayer insulating layer, 10. Plating

Claims (8)

  An adhesive comprising (a) a polyamideimide resin having a weight average molecular weight of 80,000 or more, (b) a polyamideimide resin having a weight average molecular weight in the range of 10,000 to 50,000, and (c) a thermosetting component. An adhesive for a multi-wire wiring board, characterized in that the glass transition point (Tg) of the cured product is 180 ° C. or higher.   The mass ratio of (a) :( b) is in the range of 30:70 to 70:30, and the mass ratio of (a) + (b) :( c) is in the range of 100: 10 to 100: 150. The adhesive for multi-wire wiring boards according to claim 1, wherein the adhesive is provided.   The multi-wire wiring board according to claim 1 or 2, wherein the end of the polyamideimide resin of (b) is an isocyanate group, and the isocyanate group is bonded to a mask agent that dissociates by heating. Adhesive.   (C) The thermosetting component contains one or more types of epoxy resins, and contains a curing agent for the epoxy resin or a curing accelerator for the epoxy resin. The adhesive agent for multi-wire wiring boards as described in 2.   The adhesive for multi-wire wiring boards according to claim 4, wherein at least one of the epoxy resins is liquid at room temperature (25 ° C).   An insulating substrate or a substrate on which a conductor circuit is formed in advance, an adhesive layer made of the adhesive for a multi-wire wiring board according to any one of claims 1 to 5, an insulating coated wire fixed by the adhesive layer, and a desired A multi-wire wiring board comprising: a through hole provided at a location of   The process of forming the contact bonding layer which consists of an adhesive agent for multi-wire wiring boards in any one of Claims 1-5 on the insulation board | substrate or the board | substrate which formed the conductor circuit previously, an insulation coating wire on the said adhesion layer After wiring and fixing, a step of heating and pressing the substrate to cure the adhesive layer, a step of forming a hole in a desired portion of the substrate and plating the inner wall of the hole to form a conductor circuit A method for producing a multi-wire wiring board.   8. The method of manufacturing a multi-wire wiring board according to claim 7, wherein in the step of heat-pressing the substrate to cure the adhesive layer, heat treatment is further performed after the heat-pressing.

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