JPH01197549A - Adhesive for wiring board - Google Patents

Abstract

PURPOSE:To obtain the title adhesive suppressed in delay of propagation and improved in a wiring density, by dissolving a mixture of an organic solvent- soluble fluorocarbon resin with a filler in an organic solvent. CONSTITUTION:A mixture of a fluorocarbon resin (A) having a low specific dielectric constant and being soluble in an organic solvent with a filler (B) and a curing agent (C) for component A is dissolved in an organic solvent (D) to obtain the title adhesive having a melt viscosity (100 deg.C) of 10<4>-10<7>P in a tack-free state. This adhesive is useful as an adhesive for a wiring board in which the necessary wiring pattern is made of an insulated wire.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an adhesive used for wiring boards (hereinafter referred to as multi-wire wiring boards) using insulated wires for necessary wiring patterns.

(Conventional technology) Multi-wire wiring boards are produced by forming an adhesive coating on an insulating substrate with an inner layer circuit formed thereon by laminating or coating it, and then running insulated wires using a numerically controlled wiring machine and simultaneously heating and melting it using ultrasonic vibrations. After gluing (hereinafter referred to as wiring) by
It is manufactured by laminating prepreg to fix an insulated wire, drilling a through hole across the wire, and forming an electroless plated metal layer on the inner wall of the hole.

Since this multi-wire wiring board uses insulated wires, the wires can cross each other on the same plane, and the wiring capacity per layer is about twice that of a general printed wiring board.

In addition, since the insulated wires are installed directly on the board, artwork unlike general printed wiring boards is not required, and design changes are easy.

The adhesive coating used for this multi-wire wiring board needs to be able to easily wire and fix insulated wires, and have heat resistance and insulation properties. For this reason, adhesives are made of natural rubber or synthetic rubber with excellent adhesive properties as the main component, cross-linked with alkylphenol resin to improve heat resistance and insulation, and further mixed with epoxy resin and various fillers as appropriate. It is used in the Special Publication No. 45-21434. Special Public Service 1977
-2063.

(Problems to be Solved by the Invention) In recent years, in order to apply multi-wire wiring boards to electronic devices that have become increasingly dense, it has become necessary to perform wiring at a higher density than before. That is, the wiring density of the conventional multi-wire wiring board was three wires between through holes spaced at 2.degree. 54 mm intervals, but in the future, a wiring density of five or more wires will be required. For this reason, the conductor diameter of insulated wires has traditionally been 0.
．． o, QI3m where it was 10~0.16mm
Must be less than m. Additionally, insulated wires must be placed in precise positions. However.

When using conventional adhesives, the adhesive resin, which is heated and melted after wiring, is fluid! l! I-edge wires may move in the direction of resolving the stress applied during wiring, and in order to suppress this movement, the adhesive force will decrease if the viscosity of the adhesive is increased and fluidity is lost. A problem arose. Furthermore, 1. Normally, about half of the cross section of insulated wires on multi-wire wiring boards is embedded in the adhesive layer, and when the dielectric constant of conventional adhesives becomes high-density wiring, was large enough to reduce the propagation speed of the signal.

The present invention solves the following drawbacks and provides an adhesive suitable for use in high-density multi-wire wiring boards, which has electrical performance superior to that of conventional adhesives.

(Means for Solving the Problems) The present invention has a composition comprising a fluororesin and a filler that are soluble in an organic solvent, and has a melt viscosity of 10' at 100°C in a semi-cured state.
The present invention relates to a wiring board adhesive characterized in that the adhesive has a bonding capacity in the range of ~107 Boas.

Insulating substrates that can be used in the present invention include all insulating substrates that can be used in conventional multi-wire wiring boards, such as glass cloth epoxy resin copper-clad laminates, glass cloth polyimide resin copper-clad laminates, etc. A power supply layer and a ground layer are formed by a known etching method, and prepregs such as glass cloth epoxy resin or glass cloth polyimide resin are laminated and cured by heating.

As a component of the adhesive coating film according to the present invention, a fluororesin that is soluble in an S-containing solvent is used, which has a small dielectric constant, is easy to form a coating film, and has improved adhesive strength to a substrate. These commercially available products include Lumiflon LF-100, LF-200, LF
-300, LF-400 (Asahi Glass Co., Ltd., trade name), etc. can be used.

These are "Organic Synthetic Chemistry" No. 42S published in 1984.
As described in No. 9, pages 841 to 849, 8×: halogen, R-nialkyl group, cycloalkyl group R° niomega-hydroxyethyl group -4CHt 3--
It has a structure called OR, dissolves in aromatic or ketone organic solvents, and can be crosslinked with the OH groups it contains and a curing agent such as melamine or isocyanate.

As a blocked isocyanate, Coronate 2503
．． 2507, 2515. Coronate AP staple,
Millionate MS-50 (Japan Polyurethane Industry Co., Ltd., trade name), Fleran Ul.

UT, Desmodule AP Stable, CT Staple, BLIloo, BL]265. BL3175 (Sumitomo Bayer Urethane Co., Ltd., trade name) is available as an epoxy curing agent.

Acid anhydrides, dicyandiamide, etc. can be used.

In addition, as the alkylated melamine in the latter combination, methylated melamine resin Melan 520, 521
,522.523 (Hitachi Chemical Co., Ltd., product name)
Alternatively, butylated melamine resin Melan 20, 22,
23, 25, 26, X65. X66 (trade name, Hitachi Chemical Co., Ltd.) can be used, and the epoxy curing agent in this case is preferably a mixture of an imidazole derivative and an acidic organic compound in order to increase heat resistance.

Commercially available products include 2PZ-CN,S (1-cyanoenal-2-phenylimidazole trimellitate) (
Shikoku Kasei Kogyo Co., Ltd. (product name), etc.

Mica, which is also effective in adjusting the flow properties of adhesives,
Finely powdered silica, zirconium silicate, magnesium silicate, white titanium, calcium carbonate.

Inorganic fillers such as aluminum hydroxide powder, short glass fibers, and glass powder, and organic polymer fine powders and particles such as silicone rubber particles, tetrafluoroethylene resin powder, and polyimide resin powder are appropriately added as fillers.

In the present invention, an adhesive solution is prepared by kneading an organic solvent, a fluororesin, a curing agent, and a filler using a kneader or a triple roll. The 1M solvent used is methyl ethyl ketone,
Acetone, toluene, xylene, methyl isobutyl ketone, ethyl acetate, methyl cellosolve, cellosolve acetate,
Those selected from among dimethylformamide, etc., and combinations thereof are used. In addition, it is preferable to add a catalyst for electroless plating to improve the adhesion of plating to the inner walls of through holes, etc. ``To form an adhesive coating on an insulating substrate, dip the insulating substrate in an adhesive solution and pull it up. It can be carried out by a method of coating on a polypropylene film or a polyester film subjected to mold release treatment, drying it, and then pressing and laminating it together with an insulating substrate.

The adhesive provided on the insulating substrate in this way.

It is necessary to control the type and amount of the curing agent and filler and the curing conditions so that the melt viscosity at 100° C. is in the range of 10 4 to 10' poise. The reason why this melt viscosity is set to 10' poise or more is that if it is lower than that.

The adhesive was too soft during the heat curing process after wiring.

This is because the insulated wire moves due to the stress left when it is wired, and the IO? The reason why it is set to be less than Poise is that if it is more than that, the adhesive will be too hard and the insulated wire will not be fully embedded in the adhesive during wiring.

This is because the adhesive strength is weak.

To adjust the viscosity to this level, the viscosity obtained by controlling the type and amount of hardening agent, filler, and curing conditions is determined in advance using a Koka type flow tester, etc., and the conditions are observed during one operation. However, in this case, the method of adjusting the viscosity by adjusting the degree of crosslinking with a curing agent is not preferable because crosslinking progresses over time.

(effect) The adhesive provided on the insulating substrate in this way.

Since its composition consists of a fluororesin and a filler that are soluble in organic solvents, the hardening agent and filler are used so that the dielectric constant is small and the melt viscosity at 100°C is in the range of 10' to 10' poise. Since the type, amount, and curing conditions of the insulated wire are controlled, there is less movement of the insulated wire due to the stress left after wiring during the heat curing process after wiring, and the insulated wire is sufficiently bonded during wiring. It is embedded in the adhesive and provides the necessary adhesive strength.

Example 1 After kneading the compounds shown below using three rolls, an adhesive was prepared in which the solid content was adjusted to 40 to 45% using a solvent containing xylene and cellosolve acetate mixed at a ratio of 1:1. , apply this adhesive to a polyester film that has been subjected to mold release treatment so that the thickness is 120 to 150 μm,
The adhesive sheet is dried by heating under conditions such that the melt viscosity at 100°C is in the range of 10' to 10'' poise.

[Adhesive compound]

Lumiflon LF-400 (Asahi Glass Co., Ltd., trade name):
100.0 parts by weight Melan 523 (Hitachi Chemical Co., Ltd., trade name): 4.
0 parts by weight Metabrominated benzoic acid (Aldrich, trade name): 0.5
Part by weight Crystallite (Tatsumori Co., Ltd., trade name) Near, 0 Part by weight Erosil (Japan Aerosil Co., Ltd., trade name) = 1.8
Weight part AGP-01/BZ (Asahi Siebel Co., Ltd.)

(Product name): 1000 parts by weight glass cloth epoxy copper clad laminate MCL-E-168 (Hitachi Chemical Co., Ltd., trade name) is etched to form an inner layer circuit and used as a catalyst for plating.Glass cloth epoxy resin prepreg GEA -168N (Hitachi Chemical Co., Ltd., trade name) was layered and an insulating substrate was laminated and formed by heating and pressing.9 The prepared adhesive sheet was bonded to the insulating substrate.

The polyester film subjected to mold release treatment was peeled off, and an insulated type 1HAW-[MW-0,1
(Hitachi Cable Co., Ltd., trade name) is wired onto an insulating board using a wiring machine.

Glass cloth epoxy resin prepreg GEA-168N (
(Hitachi Chemical Co., Ltd., trade name) is layered on a structure in which insulated wires are laid on an insulated substrate.

Laminate molding by heating and pressurizing.

Hitarefus S-500X-9, a polyethylene film with adhesive, was used as a plating mask on the laminated molded product.
(Hitachi Chemical Co., Ltd., trade name) was laminated, holes were made where the through holes should be made, and then immersed in the electroless plating solution H320IB (Hitachi Chemical Co., Ltd., trade name) for 10 minutes. After plating was performed using an electroless plating solution with the following composition at a solution temperature of 68° C. and an immersion time of 30 hours to form a copper layer of about 35 μm thick on the inner wall of the hole.

The plating mask was peeled off to obtain a multi-wire wiring board.

[Electroless plating solution composition]

Copper sulfate: 10. Og/l Sodium ethylenediaminetetraacetate: 35. Og/j! 37% formalin: 5.0m1/1 Sodium cyanide: 40. Omg/7+FC-128
(Sumitomo 3M Limited, product name): 0. 1 g/l Sodium hydroxide: amount such that the pH of the above solution is 12.0 In the multi-wire wiring board thus obtained, the relative dielectric constant of the adhesive is 2.8, and the intersection of two insulated wires The propagation delay was +6.0 nsec/m in the part where the characteristic impedance was 50 Ω, which was an improvement of about 10% compared to a multi-wire wiring board using a conventional adhesive.

In addition, the effect of implementing one wire is approximately 2000 wires,
Ten wiring boards were made, three at right angles and one at a 45 degree diagonal between through holes with a fabric density of 2.54 mm, but there were no breaks at intersections during wiring. Even after 200 cycles of testing specified in MIL-3TD-202E-107C, there were no failures in the connections.

(Effect of the invention) As explained above, organic? By using a composition consisting of a fluororesin and a filler that is soluble in fI, and whose melt viscosity at 100°C in a semi-cured state is in the range of 104 to 107 Boas, it is possible to reduce propagation delay and create a multi-layer structure with excellent wiring density. An adhesive for wire wiring boards can be provided.

Claims (1)

[Claims] Its composition consists of a fluororesin and a filler that are soluble in organic solvents, and its melt viscosity at 100℃ in a semi-cured state is 10^4~10^
Adhesive for wiring boards in the 7 poise range.