JPH07119088B2 - Manufacturing method of printed wiring board - Google Patents

Description

The present invention relates to a method for manufacturing a printed wiring board substrate.

[Conventional technology]

Conventionally, a precondensate composed of bismaleimide and 4,4'-diaminodiphenylmethane is mainly used as a polyimide used for a heat-resistant adhesive. Since this polyimide has poor storage stability in a solution state, it is handled as a powder, and when it is used for manufacturing a substrate for a printed wiring board, it is once used in a state of being dissolved in a solvent.

[Problems to be Solved by the Invention]

However, since this polyimide itself is hard and brittle, it cannot be cast into a film.

On the other hand, as polyimides, thermoplastic ones such as polyether imide are known, but they have a drawback that they are not cured and therefore, once molded, they are deformed by heat.

Therefore, it has been difficult or unsuitable to use the film-shaped polyimide adhesive in the production of the printed wiring board substrate.

[Means for Solving the Problems]

The present invention has the general formula [Where Ar is the formula (a)] Or formula (b) And a group of the formula (a) and a group of the formula (b), the latter / the former having a molar ratio of 0/100 to 90/10.
(A) and general formula (However, in the formula, m is an integer of 2 or more, and R is an m-valent group having 2 or more carbon atoms.) The polymaleimide (B) is represented by the polymaleimide (B) with respect to the polyimide (A). Is 10
Relates to a method for producing a printed wiring board substrate, which comprises bonding a base material and a copper foil using a thermosetting film-like adhesive obtained by casting a composition containing 50 wt% of the composition. .

In the present invention, the polyimide (A) is 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride (hereinafter abbreviated as BTDA) and bis (4- (3) in a solvent such as cresol, phenol, or toluene. It can be obtained by heating and stirring -aminophenoxy) phenyl) sulfone (hereinafter abbreviated as m-APPS), which is reacted in an aprotic polar solvent such as dimethylacetamide or dimethylformamide at a temperature of room temperature or lower, It can also be obtained by synthesizing a polyamic acid and performing dehydration ring closure using a dehydrating agent such as acetic anhydride-pyridine.

In the above, as the diamine, in addition to m-APPS,
2,4-diaminotoluene (hereinafter abbreviated as 2,4-DAT) can be used in combination.

In the polyimide (A), m-APPS and 2,4-DAT are in a molar ratio.
It is preferable that 2,4-DAT / m-APPS is contained in a ratio of 0/100 to 90/10. When the content of 2,4-DAT is more than 90 mol%, not only the polyimide (A) becomes hard and the moldability of the composition deteriorates, but also the flexibility of the film adhesive is deteriorated.

Specific examples of the polymaleimide (B) that can be used in the present invention include N, N- (4,4'-diphenylmethane) bismaleimide, N, N '-(4,4'-diphenyloxy) bismaleimide, N, N'-p-phenylene bismaleimide, N,
N'-m-phenylene bismaleimide, N, N'-2,4-tolylene bismaleimide, N, N'-2,6-tolylene bismaleimide, N, N'-ethylene bismaleimide, N, N'-hexamethylene bismaleimide, etc. There are polymaleimides represented by structural formulas such as, and these can be used alone or in combination of two or more.

The mixing ratio of the polyimide (A) and the polymaleimide (B) is such that the polymaleimide (B) is relative to the polyimide (A).
It is preferably selected within the range of 10 to 50% by weight. If the amount of the polymaleimide (B) is less than 10% by weight, the curing will be insufficient, and if it exceeds 50% by weight, not only the moldability of the composition will be poor, but also the flexibility of the film adhesive will be poor.

The polyimide (A) and the polymaleimide (B) may be mixed in a powder form, but normally, the polyimide varnish obtained by dissolving the polyimide (A) in a solvent such as cresol, phenol, dimethylformamide, or toluene is used. (B) is added and dissolved.

The composition thus obtained can be cast on a glass plate, a stainless plate or the like and dried to prepare a film-like adhesive containing no base material, which can also be used for various purposes. In this case, the drying temperature and time differ depending on the solvent used and the type of polymaleimide (B), but it is necessary to keep the temperature lower than the temperature at which the polymerization of polymaleimide (B) becomes remarkable, and the time is the amount of residual solvent. Should be less than about 1%.

A substrate for a printed wiring board can be obtained by heating and pressing the above film-like adhesive between a copper foil and a base material such as an aluminum plate or a polyimide film. The heating temperature at this time is preferably a temperature equal to or higher than the softening point of the film adhesive, and the film adhesive is cured and reacted.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to Examples, but the scope of the present invention is not limited to these Examples.

Example 1 BTDA32.2g, m-APPS21.6g, 2,4-DAT6.1g was placed in a four-necked flask equipped with a stirrer, thermometer, nitrogen gas introduction tube, cooling tube, m-cresol 539g, 108 g of toluene was added, and the mixture was heated and stirred while flowing nitrogen gas. At 150-160 ℃
After reacting for 16 hours, a polyimide varnish having a resin content of 17.8% and a viscosity of 15P was obtained. 100g of this polyimide varnish contains N, N'-
3.54 g of (4,4'-diphenylmethane) bismaleimide was dissolved to obtain a resin composition. The resin composition did not gel even after being stored at room temperature for 1 month. This resin composition was cast on a glass plate and dried at 160 ° C. for 30 minutes to give a thickness of 25 μm.
m flexible uncured film was obtained. 25 this film
A tough cured film was obtained by heating at 0 ° C. for 30 minutes. The cured film did not melt even when placed in a solder bath at 300 ° C.

The resin composition (varnish) is cast on a glass plate,
After drying at 30 ° C. for 30 minutes, a film-like adhesive having a thickness of 25 μm was obtained. Apply this film adhesive to a 1mm thick aluminum plate and 35μm
It was sandwiched between thick copper foils and pressed under the conditions of 50 kg f / cm ² , 250 ° C. and 30 minutes to obtain a laminate. Copper foil peeling strength is 2.5k
It was gf / cm, and it did not swell or peel even when immersed in solder at 300 ° C for 60 seconds.

Examples 2 to 4 and Comparative Examples 1 to 2 BTDA32.2g, m-APPS21.6g, and 2,4-DAT6.1g were placed in a four-necked flask equipped with a stirrer, a thermometer, a nitrogen gas introducing pipe, and a cooling pipe. Add 539 g of m-cresol and 108 g of toluene,
The mixture was heated and stirred while flowing a nitrogen gas. The reaction was carried out at 150 to 160 ° C for 16 hours to obtain a polyimide varnish having a resin content of 17.8% and a viscosity of 15P. This polyimide varnish was poured into acetone, reprecipitated, pulverized, washed and dried to obtain a polyimide powder. Reduced viscosity of polyimide powder (concentration 0.1 g / dl,
Solvent N, N-dimethylformamide (DMF), temperature 30.0 ° C]
Was 0.72 dl / g. Obtained polyimide powder 100g and N,
N '-(4,4'-diphenylmethane) bismaleimide (BM
I) 10 g was dissolved in 400 g DMF to obtain a varnish. The varnish was cast on a glass plate, dried at 130 ° C., peeled off, fixed on an iron frame and dried at 200 ° C. for 1 hour to obtain a film-like adhesive (used in Example 2). The obtained film-like adhesive has a thickness of 25 μm, a residual solvent amount of 1% and a softening point of 230 ° C.
It was excellent in flexibility without breaking even when it was bent at an angle of °.

In addition, a film-like adhesive was obtained in the same manner as above except that the BMI amount was changed as shown in Table 1.

Table 1 shows the softening points of these film adhesives.

Apply these film adhesives to an aluminum plate of 1mm thickness and 35μm
50 kg f / cm ² , 275 ℃, 30 sandwiched between thick single-sided roughened copper foils
A copper clad substrate was obtained by stacking under the conditions of minutes. The characteristics of each substrate are shown in Table 1.

The BMI amount indicates the used weight part (phr) of BMI with respect to 100 parts by weight of polyimide.

The softening point was measured by the penetration method at a load of 25 kg f / cm ² and a heating rate of 10 ° C / min.

The copper foil peeling strength was measured at a pulling speed of 50 mm / min and a 90 ° peeling strength.

The solder heat resistance was evaluated by observing the presence or absence of blistering after floating a 20 mm square test piece on the solder bath with the copper foil facing down, and evaluating the absence of blistering as ◯.

Example 5 One sheet of the same film adhesive as used in Example 2 was sandwiched between a 50 μm thick polyimide film and a 35 μm thick single-sided roughened copper foil, and 275 ° C., 50 kg f / cm ² , The substrates were laminated under the condition of 30 minutes to obtain a substrate for flexible printed wiring board. The 90 ° copper foil peeling strength of this substrate was measured at a pulling speed of 50 mm / min and found to be 2.8 kg f / cm at room temperature and 2.4 kg f / cm at 150 ° C. Further, the board was immersed in a solder bath at 300 ° C. for 1 minute, but no blistering occurred.

Example 6 A film adhesive was prepared in the same manner as in Example 2 except that the BMI amount was 30 phr. This film-like adhesive and 35 μm single-sided roughened copper foil were laminated on both sides of a 50 μm-thick polyimide film and laminated under the conditions of 275 ° C., 50 kg f / cm ² and 30 minutes to obtain a substrate for flexible printed wiring board.

The 90 ° copper foil peeling strength of this substrate is 2.5 kg f / cm, 150 at room temperature.
The temperature was 2.3 kg f / cm, and no blistering occurred even when immersed in a solder bath at 300 ° C for 1 minute.

Example 7 A flexible printed wiring board was prepared in the same manner as in Example 5 except that a film-like adhesive produced in the same manner as in Example 2 was used except that BMI-M (polymaleimide manufactured by Mitsui Toatsu Chemicals Inc.) 15 g was used instead of BMI. A substrate for use was obtained. The 90 ° copper foil peeling strength of this substrate is 2.5 kg f / cm at room temperature and 2.1 kg f / cm at 150 ° C.
No blistering occurred even when immersed in a solder bath at 300 ° C for 1 minute.

Comparative Example 3 Pyrralux (acrylic film adhesive manufactured by Dupont) was used in place of the film adhesive, and laminated in the same configuration as in Example 5 under the conditions of 180 ° C., 300 kg f / cm ² and 60 minutes,
A flexible printed wiring board substrate was obtained. The 90 ° copper foil peeling strength of this substrate is 2.2kg f / cm at room temperature and 0.6kg f / cm at 150 ° C.
It was. When this board was immersed in a solder bath at 300 ° C for 1 minute, swelling occurred.

Reference Example 1 A film was prepared in the same manner as in Example 2 except that 20 g of BMI-M (polymaleimide manufactured by Mitsui Toatsu Chemicals, Inc.) was added instead of N, N '-(4,4'-diphenylmethane) bismaleimide. An adhesive adhesive was obtained. The resulting film adhesive has a thickness of 25
μm, residual solvent amount 1.1%, softening point 235 ℃, it was excellent in flexibility without breaking even when bent 180 °.

Comparative Reference Example 1 A varnish prepared by dissolving 100 g of Kellimide 601 (polyamino bismaleimide resin manufactured by Nippon Polyimide Co., Ltd.) in 100 g of DMF was cast on a glass plate, dried at 130 ° C. for 10 minutes, and then dried at 170 ° C. for 20 minutes, but the film was brittle. It was unattainable.

〔The invention's effect〕

The printed wiring board substrate obtained according to the present invention has excellent peel strength and heat resistance.

Claims (1)

[Claims] 1. A general formula [Where Ar is the formula (a)] Or formula (b) And a group of the formula (a) and a group of the formula (b), the latter / the former having a molar ratio of 0/100 to 90/10.
(A) and general formula (However, in the formula, m is an integer of 2 or more, and R is an m-valent group having 2 or more carbon atoms.) The polymaleimide (B) is represented by the polymaleimide (B) with respect to the polyimide (A). Is 10
A method for producing a printed wiring board substrate, which comprises bonding a base material and a copper foil by using a thermosetting film adhesive obtained by casting a composition containing 50% by weight to 50% by weight. .