JPH02237095A - Manufacture of heat-resistant printed wiring board - Google Patents

Abstract

PURPOSE:To obtain a heat-resistant flexible printed wiring board provided with an overlay which is capable of dealing with an automatic assembly line of high operational speed, excellent in dimensional stability in a hot and wet environment, soldering heat resistance, and flexibility, and simple in a manufacturing process by a method wherein the overlay is formed of specific aromatic polyamide-imide resin soluble in a polar organic solvent. CONSTITUTION:After the formation of a conductor pattern, resin solution, in which polar organic solvent soluble aromatic polyamide-imide resin obtained by reacting aromatic diamine with anhydrous trimellitic chloride in a polar organic solvent and filler, if necessary, are dispersed, is applied onto the conductor pattern to form an overlay. The used aromatic polyamide-imide resin is soluble in polar organic solvent, it is desirable that its end is hindered with aniline or the like, and its reduced viscosity is not limited if it is 0.5 or above but it is practical that the viscosity ranges from the viscosity of the solution in use to 3.5 or so. By this setup, a overlay is excellent in soldering heat resistance and other physical properties such as resistance to breakage, adhesion, and dielectric strength, and improved in reliability for long term service.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of Industry-V] The present invention relates to a method for manufacturing a heat-resistant printed wiring board (particularly a flexible heat-resistant printed wiring board). More specifically, it relates to a method for producing a heat-resistant pudding 1 to a wiring board (particularly a heat-resistant flexible phosphor 1/wiring board), which is characterized by using a polar organic solvent-soluble aromatic polyamide-imide resin or a composition thereof as a coverlay. It is something.

(Conventional technology) Electronics and electronics application equipment is rapidly becoming smaller, lighter, and more sophisticated. One thing that supports this progress
There has been significant progress in materials for peripheral parts. In particular, advances in printed wiring boards have been dramatic, and have greatly influenced the above-mentioned miniaturization, weight reduction, and performance improvement. Recently, flexible printed wiring boards have been attracting attention, and further improvements in -m have been desired.

In other words, printed wiring boards must have high heat resistance to withstand processes such as half-[[] Moreover, it has flexibility (flexibility).
When it comes to materials that have both beats and quadruple beats, this has not yet been achieved.

At present, the closest thing to these requirements is to pattern and edge a flexible copper-clad board made by bonding copper foil to a polyimide film, and then use a coverlay film (polyimide film with adhesive, pre-perforated with Kinsei). II: @Some products are manufactured by coating (edited by Electronic Materials Editorial Department [Princess 1/Wiring Technology J June 10, 1983)
Japan, Published by the Industrial Research Council: Reference).

However, since this product also uses adhesive to cover the coverlay, the heat resistance of the polyimide is not fully utilized, resulting in unsatisfactory soldering heat resistance.
Furthermore, due to the hygroscopic nature of the polyimide resin, problems such as "blistering" may occur if the dry aging process is not completed.

In addition, polyimide is an expensive resin to begin with, so the spouts that occur when punching out a mold with a mold are significant, and this increases the mold cost and labor needed to accommodate a wide variety of patterns, making it expensive. It had the disadvantage of being too large.

In addition, overcoating methods using coating agents such as half-tIl resists, which are simple and inexpensive, have been developed, but they either have extremely low heat resistance or lack flexibility, and are inexpensive. However, in terms of performance, it does not reach the level of the polyimide-based printed wiring board mentioned above.

[Problem to be solved by the invention]

Under these circumstances, the present inventor developed a product that has dimensional stability in hot and humid conditions, soldering heat resistance, excellent flexibility, and is easy to process, making it compatible with increasingly high-speed automatic assembly lines. In order to provide a heat-resistant printed wiring board, especially a heat-resistant flexible printed wiring board, using a coverlay (cover coat), as a result of extensive research, we have found that a specific polar organic solvent-soluble aromatic poly7amide-imide resin is used. The inventors have discovered that the object can be achieved by the following methods, and have arrived at the present invention.

[Means to solve the problem]

That is, in the present invention, after forming a conductor pattern, a polar organic solvent-soluble aromatic polyamideimide resin obtained by reacting an aromatic diamine and anhydrous trimellitic acid chloride in a polar hi solvent and, if necessary, a filler is dispersed. The present invention provides a method for manufacturing a heat-resistant printed wiring board, which comprises applying a resin solution on the conductive pattern to form a coverlay.

The present invention also provides a method for producing a heat-resistant printed wiring board in which the effect is further improved by adding a specific filler to the aromatic poly7imide resin.

The present invention will be explained in detail below.

The aromatic polyamideimide resin used in the present invention is a polar solvent-soluble aromatic polyamideimide resin, and has the general formula (where X is an M atom, a methylene group, a sulfur atom, a sulfonyl group, or a carbonyl group). and n represents an integer of 2 or more) or a mixture thereof. Among these, particularly preferred are those in which X is an oxygen atom.

Further, it is particularly preferable that the aromatic polyamideimide of the present invention has its terminal end-blocked with aniline or the like.

The reduced viscosity of the aromatic polyamideimide resin used in the present invention is not particularly limited as long as it is 0.5 or more, but it is practical to have a reduced viscosity of about 3.54J compared to the solution viscosity at the time of use.

If the reduced viscosity is too low, the mechanical strength and flexibility will be reduced, and if the reduced viscosity is too high, the solubility in polar organic solvents will be reduced, making it impractical.

In addition, when used in the form of so-called ink dissolved in a polar organic solvent, the ink viscosity is 100 to 3000.
A poise ink is preferred, and the ink concentration at that time is preferably 5% to 30% resin.

These aromatic polyamideimide resins can be prepared by known methods,
For example, it can be produced by (1) reacting an aromatic diamine with trimellitic anhydride chloride, or (2) reacting an aromatic diisocyanate with trimellitic anhydride.

Among these, reaction (2) will be explained below as a representative example.

(8) l-12N-@-X-@-N+-12(
(X in the formula has the same meaning as above), or (m-phenylenediamine), any one of (A) and (B) aromatic diamine and trimellitic anhydride chloride, N,N-dimedylacetamide, The reaction is carried out in a polar organic solvent such as N-methyl=2-pyrrolidone. It is important to optimally control the amidation and imidization reaction steps, especially the reaction temperature, during the reaction process.

As the aromatic diamine (A), 4,4"-diaminodiphenyl ether is particularly preferred, but phenyl sulfide, 4,4"-diaminodiphenyl sulfone, 4,4"-diaminodiphenyl ether, and
．． 4'-diaminobenzophenone and the like can also be used.

Further, among the aromatic diamine (A) and the aromatic diamine (8), the aromatic diamine (A) is more preferable because it has excellent flexibility, heat resistance, and moisture resistance.

Examples of the polar organic solvent for the aromatic polyamide-imide resin of the present invention include N,N-dimedylformamide, N,N-dimedylacetamide, dimedyl sulfoxide, N-methyl-2-pyrrolidone, and hexylymethylphosphoramide. , a halogenated cresol, a mixed solvent thereof, or a mixed solvent of these and a commonly used solvent.

Note that among these, particularly preferred is N-Mejiru 2-
pyrrolidone and N. N-dimethylacetamide.

Next, in the present invention, fillers to be added in order to exhibit better effects are appropriately selected from the following three types.

■High thermal conductivity filler: Thermal conductivity is 0.05 cal/c
m. sec. It is a highly thermally conductive inorganic filler with grade C or higher.

Specific examples include Berilla (Bed), Magnesia (
MgO), boron nitride (BN>, alumina (81203)
), silicon carbide (S i C), silicon nitride (Si3
N4), carbon (C) and mixtures thereof. Further, in consideration of toxicity, moisture resistance, and insulation, boron nitride or alumina is particularly recommended as a filler.

■ Conductive metal fine powder: Specifically, fine powder selected from gold, silver, platinum, copper, nickel, aluminum, silicon, molybdenum, iron, cobalt, tungsten, titanium, zinc, alloys of these, and mixtures thereof. Use.

(2) Mica: Natural mica or synthetic mica The shape of these fillers is not particularly limited, and any shape such as spherical, angular, chime-like, layered, scale-like, etc. can be used. Further, the particle size can be used as long as it is a so-called fine powder, but it is usually 200 μm or less, particularly preferably 50 μm or less.

The blending ratio of the filler is 1 to 35% by volume, preferably 5 to 25% by volume. If the blending ratio of the filler is too high, mechanical strength and flexibility will decrease, and if it is too low, the effect of improving heat resistance and moisture resistance will be small. Therefore, if the blending ratio of filler is too low, curling will occur during the solder heat resistance test under more severe conditions.

Note that the optimum blending amount will vary depending on the intended use, filler shape, and particle size, so the relationship between the physical properties of the filler to be used and the blending ratio should be preliminarily determined through experiments.
It is recommended that formulations be determined based on this.

Conventionally known methods can be used to produce the composition containing the filler of the present invention. For example, it can be produced by adding an aromatic polyamide-imide resin to a polar organic solvent, dissolving it completely, adding a filler, and uniformly dispersing it using a stirrer, a ball mill, a three-necked mill, etc.

Various other additives can be added to the coverlay of the present invention, if necessary. For example, silane coupling agents, glass powder, glass fibers, heat-resistant fibers, interfacial agents, etc. may be added to enhance adhesion, mechanical strength, or other properties.

The method for manufacturing a printed wiring board of the present invention will be explained using a flexible printed wiring board as an example where the features of the present invention are most fully exhibited.

A flexible printed wiring board is prepared by laminating a conductive material such as copper foil onto a film or sheet made of a polyimide resin, poly(mide) resin, polyester resin, or a glass material impregnated with a poxy resin. This is patterned by photoresist method or screen printing method,
Next, unnecessary copper foil other than the wiring pattern is dissolved and removed using chemicals to form a copper circuit board.

Next, the polar organic solvent-soluble aromatic polyamide-imide resin of the present invention used as a coverlay or its composition was applied onto the circuit board in a predetermined pattern by screen printing, and the coating was further heated and cured. By removing the solvent from the resin or its composition, a flexible printed wiring board with a coverlay provided thereon is produced.

Although this screen printing method is the preferred method, it is also possible to prepare a film in advance using the polar organic solvent-diluted bamboo aromatic polyamide-imide resin of the present invention and a composition containing the same. It is also possible to manufacture the parts by punching and cutting them in a predetermined pattern, placing them correctly on the circuit surface (alignment t!), and then hot-rolling them.

〔Example〕

Next, the present invention will be explained with reference to Reference Examples, Examples, and Comparative Examples.

Reference example 1: Production example of heat-resistant insulating ink A 4, 4°-diaminodiphenyl ether (DADPE) Polar organic solvent soluble aromatic polyamideimide (FAI: reduced) synthesized from trimellitic anhydride (1-MAC) Viscosity: 1.3) Heat-resistant insulating ink A was prepared by adding N-methyl-2-pyrrolidone (NMP>400 parts) to 100 parts (viscosity: 1.3) and dissolving the PAI in NMP.

Reference Example 2: Production example of heat-resistant insulating ink B Similar to Example 1, aromatic poly-7mide-imide (PAI: reduced viscosity 1.4) soluble in polar organic solvent was synthesized from DADPE and TMAC.
) Add 470 parts by weight of NMI to 100 parts by weight of P
Dissolve AI in NMP.

Next, boron nitride (manufactured by Showa Denko, particle size 1.7 μm)
Mix the most part of the 17-layer with the above PAI resin solution, and
1 q of heat-resistant insulating ink B was uniformly dispersed using one machine.

Reference example 3: Production example of heat-resistant insulating ink C Polar ink synthesized from DADI) E and TMAC & solvent-soluble aromatic polyamide-imide (PAI: reduced viscosity 1.4) 100
Add 490 parts by weight of NMP to the heavy part to dissolve the PAI.

Next, mica (manufactured by Tamaki Mica Co., Ltd., particle size 46 μm)
) A solution prepared by dispersing 48 parts by weight of NMP in 90 parts by weight of NMP was mixed with the above FAI resin solution, and the heat resistant insulating ink C was obtained by uniformly dispersing the force using a seconder.

Reference example 4: Production example of heat-resistant insulating ink D DADPE and l
Polar '4-i organic solvent soluble aroma storage polyamideimide (PAI: far zt viscosity! 1.5 > 1) synthesized from MAC
Add 20 parts by weight of NMP and 480 parts by weight,
The PAI is dissolved in NMP. Next, a solution prepared by dispersing aluminum powder (average particle size 15 μm, fine for ALC manufactured by Fukuda Metal Powder Industry Co., Ltd.) in 54 parts by weight of NMP (108 parts by weight) and the above PAI resin solution were mixed, and the aluminum powder was mixed with a seconder. A heat-resistant insulating ink D was obtained by uniformly dispersing the mixture.

Reference Example 5: Production example of heat-resistant insulating ink E 100 parts of polar organic solvent-soluble aromatic polyamideimide (PAI: reduced viscosity 1.0) synthesized from m-phenylenediamine (m-PD) and -rMAC 400 parts by weight of NMP was added to dissolve PAI in NMP to obtain heat-resistant insulating ink E.

Example: Ordinary single-sided body panel for flexible printed circuit boards (copper foil thickness: 35μrn, Kapton thickness: 25μm, adhesive thickness: 25μT)
An etching pattern was formed by the photoresist method using (rL), followed by etching with a ferric chloride solution, and the etching resist was further removed to obtain a wiring circuit pattern.

Next, heat-resistant insulating ink A. B. C. D and E were printed on the wiring circuit pattern by screen printing using a line metal screen (165 mesh, emulsion thickness 10 μm) so that the film thickness of the predetermined pattern was about 10 μm. Next, this wiring circuit pattern was pre-dried on a hot plate at 80°C for 10 minutes, then fixed on an aluminum backing plate with the printed side facing up, heat-treated at 250°C for 10 minutes, and then heated with a solvent. 19 by removing the flexible wiring circuit board.

Using the flexible wiring circuit board obtained by the above method, the solder heat resistance, folding durability, adhesion, and voltage resistance were tested under constant temperature and humidity (40°C, 90% RH) and thermal shock (-55°C, 30% RH).
Characteristics were evaluated at temperatures ranging from 30 minutes to 125°C. These results are shown in Table 1, and it can be seen that the flexible printed circuit board is excellent.

In addition, the solder heat resistance test was conducted at 300°C for 20 seconds.
When tested with a more severe straight line, warpage occurred in heat-resistant insulating inks A and E that did not contain filler. Furthermore, although the folding durability of the heat-resistant insulating ink containing one filler (for example, C) is slightly low, it should be noted that the folding durability does not pose any practical problems.

Each measurement for characteristic evaluation was performed as shown below.

■Solder heat resistance: The test piece was immersed in a 260°C solder bath for 10 seconds, and the occurrence of blistering and peeling was evaluated as 11! Inspection.

■Breakability: JIS P 811! ] According to M I
Measured with R=0.38 using a Type 1 tester and a Suju boo g.

■Adhesion: Cross force tape method, that is, creating a coating film.
Cross-cut according to the ISκbaooxidial test, and P
Apply the EI-tape, then peel it off and count the remaining squares from 1 to 100.

■Electrical resistance [: AC 500V electricity IJ- was applied to test H for 1 minute, and the presence or absence of abnormality was observed.

Comparative example: The same wiring circuit pattern was produced by the same method as in the above example, and a polyimide cover film with adhesive (Kapton (registered trademark) thickness 25 μm, adhesive 1 layer 25 μm, DuPont (manufactured by Kawasaki Co., Ltd.) was cut into a predetermined shape and processed with holes C, then laminated with a heat roll, and then heat-pressed at 50K'J/CIi and a heating temperature of 1i150℃ for 30 minutes to form a cover film. 1q of flexible wiring circuit boards with attached.

A solder heat resistance evaluation test was conducted in the same manner as in the example (260° C., 10 seconds solder bath immersion).

When a solder heat resistance test was conducted immediately after being left for 500 hours at a constant temperature and humidity of 40° C. and 90% bending, blistering and peeling occurred in all cases. Therefore, after leaving it under constant temperature and humidity,
When we conducted a solder heat resistance test by pre-drawing drying for 60 minutes at
After some time, swelling and peeling were observed.

In addition, the test results for thermal shock}-(-55°C, 30 minutes to 125°C, 30 minutes) showed that, without pre-drying (80°C, 60 minutes), blistering and peeling were observed at the Oth cycle.

It was observed that the occurrence of abnormalities (blistering, peeling) was considerably suppressed when pre-drying was performed.

As a result, it was confirmed that there is a clear difference in the solder heat resistance test, which is the most important characteristic evaluation test, from the present invention, in which no abnormality was observed even without pre-drying.

〔Effect of the invention〕

As described above, the heat-resistant printed wiring board obtained by the present invention has excellent performance in terms of solder heat resistance, which has been emphasized in recent years, and has excellent physical properties such as bending resistance, adhesion, It has excellent voltage resistance and extremely high reliability for long-term use, making it extremely effective.

In addition, the method for manufacturing a heat-resistant printed wiring board of the present invention requires a post-processing process (■-ging) that is complicated and increases costs.
It has the excellent effect of being able to employ an extremely economical and simple manufacturing method that does not require any special molds or material loss.

Applicant: Nippon Kokushi T Gyo Co., Ltd. Agent: Patent attorney: Kazuya Nozaki

Claims (3)

[Claims] 1. After the conductor pattern is formed, a resin solution in which a polar organic solvent-soluble aromatic polyamide-imide resin obtained by reacting an aromatic diamine and anhydrous trimellitic acid chloride and a filler, if necessary, is dispersed, is applied onto the conductor pattern. 1. A method for producing a heat-resistant printed wiring board, characterized by coating the board and forming a coverlay. 2. 2. The method for manufacturing a heat-resistant printed wiring board according to claim 1, wherein the filler is selected from a highly thermally conductive filler, a conductive metal fine powder, and mica. 3. 3. The method for manufacturing a heat-resistant printed wiring board according to claim 1, wherein the heat-resistant printed wiring board is a heat-resistant flexible printed wiring board.