JPH1058593A - Copper-clad laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the number of times of repeating until connection of through hole provided by punching is disconnected by a heat cycle test, and to improve connecting properties by placing a copper foil having specific elongation in tension at the time of heating on an insulation board made of paper base material and thermosetting resin. SOLUTION: Paper base material is impregnated with drying oil modified phenol resin varnish, and dried to a prepreg. Predetermined number of prepregs are superposed, copper foils are superposed on its both side surfaces, heated and pressurized to manufacture a copper-plated laminate. As the foil, it may have 3% or more of elongation in tension at 180 deg.C, and has no other limitation, and it is preferable to dispose an adhesive layer at an insulation board side by using the foil with adhesive coated, for example, with known butyral phenol resin adhesive. The obtained double-sided copper-plated laminate is punched at predetermined position to provide a through hole, and electric connection of both the surfaces is formed by plating or embedding with silver paste to form a circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper-clad laminate having a conductive paste embedded through-hole excellent in reliability when used as a printed wiring board.

[0002]

2. Description of the Related Art Recently, electronic equipment has become multifunctional and small,
In addition, high reliability is required, and printed wiring boards used in these electronic devices are also required to have good reliability. 2. Description of the Related Art As electronic devices have become more multifunctional, the number of wirings has been increased, and it has been necessary to increase the wiring density. In a double-sided printed wiring board, it is necessary to electrically connect the circuits on both sides. As a means for electrically connecting the circuits on both sides, copper or silver paste is buried in a hole (referred to as a through hole) penetrating the board (copper or silver paste through hole), or copper plating is applied to the wall of the through hole. Copper plating through holes to be applied are adopted. In any case, it is necessary to provide a through hole in the printed wiring board. However, as a means for providing a through hole in a paper base printed wiring board, which is widely used in consumer electronic devices, it is efficient to use a punching process. Has been adopted.

[0003]

However, in connection with through holes provided by punching, the number of repetitions (number of cycles) until disconnection in a heat cycle test or hot oil test is small, that is, sufficient connection reliability is obtained. There was a disadvantage that it could not be obtained. An object of the present invention is to provide a copper-clad laminate capable of obtaining a highly reliable through-hole connection even by punching.

[0004]

The present inventors have investigated the cause of disconnection in a heat cycle test or a hot oil test, and stress has been left on copper foil around a through hole by punching, and this stress has caused The present inventors have found that fine cracks were formed, and the cracks were expanded by repeated thermal expansion and contraction in a heat cycle test and a hot oil test, resulting in disconnection, and the present invention was reached. The present invention is a copper-clad laminate obtained by attaching a copper foil having a tensile elongation at 180 ° C. of 3% or more on an insulating substrate made of a paper base material and a thermosetting resin.

In the present invention, the term "tensile elongation at 180 ° C." refers to the numerical value obtained by measuring the elongation when the copper foil is cut by performing a tensile test under the following conditions. Measurement temperature: 180 ° C., pulling speed: 5 mm / min Test piece length: 200 mm, test piece width: 10 mm, initial fulcrum distance: 100 mm

## EQU1 ## Tensile elongation at 180 ° C. (%) = 100 ×
(Ab) / ba a: distance between supporting points when copper foil is cut, b: distance between initial supporting points

The tensile elongation of copper foil at 180 ° C. is 3%.
It is necessary to set it as above, preferably 4% or more, more preferably 8% or more. If the tensile elongation at 180 ° C. is small, sufficient through-hole reliability cannot be obtained.

Conventionally used electrolytic copper foil 1
The tensile elongation at 80 ° C. is about 2%. For this reason,
A large stress remains around the punch due to the punching process. On the other hand, when the tensile elongation at 180 ° C. is large, a large stress does not remain around the punch due to the punching process.
For this reason, the higher the tensile elongation during hot work is, the more preferable. However, there is a limitation both physically and in terms of production. At present, 40% of copper foil is available at the maximum.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Since through holes are provided by punching, in the present invention, a paper is used as a base material, and a thermosetting resin, in particular, a phenol resin, a melamine resin, an unsaturated polyester resin or the like is used as a matrix. Copper-clad laminates are preferred.

Above all, those using kraft paper or linter paper as a base material and a phenol resin as a matrix are most widely used. As the phenolic resin, a dry oil-modified phenolic resin modified with a drying oil is particularly preferable because of good punching workability. Drying oils used to modify the phenolic resin include tung oil, dehydrated castor oil, linseed oil and the like. As phenols, phenol, meta-cresol, para-cresol, ortho-cresol, isopropylphenol, para-tert-butylphenol, para-isopropenylphenol oligomer, nonylphenol, bisphenol A and the like are used.

[0010] A paper base material is impregnated with a drying oil-modified phenolic resin varnish and dried to form a prepreg. A predetermined number of the prepregs are laminated, copper foil is laminated on both sides thereof, and heated and pressed to produce a copper-clad laminate. As for the manufacturing conditions, conventionally known manufacturing conditions can be applied, and there is no particular limitation. The copper foil may have a tensile elongation at 180 ° C. of 3% or more, and there are no other restrictions. For example, a copper foil with an adhesive coated with a known butyral phenol resin adhesive may be used. Preferably, the adhesive layer is on the insulating substrate side.

The obtained double-sided copper-clad laminate is provided with a through hole at a predetermined position to form a through hole, an electric connection on both sides is formed by plating or embedding silver paste, and a circuit is formed by etching to form a through hole. It is a hole printed wiring board.

[0012]

【Example】

Example 1 Preparation of primary impregnated varnish 1 mol of phenol, 1.2 mol of 37% (wt%, the same applies hereinafter) formalin in terms of formaldehyde, and 0.4% of 30% aqueous triethylamine solution in terms of triethylamine.
The moles were reacted at 70 ° C. for 6 hours to obtain a water-soluble phenol resin. The obtained water-soluble phenolic resin, by weight ratio,
The mixture was diluted with a mixed solvent of water 1 and methanol 1 to prepare a primary impregnated varnish having a resin solid content of 12%. Preparation of secondary impregnated varnish Tung oil 10 in a flask equipped with a thermometer, stirrer and cooler
00 g, meta-cresol 1000 g, phenol 100
0 g and 1 g of paratoluenesulfonic acid, and charged at 110 ° C.
For 2 hours to add phenols to tung oil.
1045 g of paraform and 30 parts of methanol were added to the reaction product.
0 g and 180 g of 28% by weight ammonia water,
The reaction was performed at 0 ° C., and when the gelation time of the reaction product (measured on a hot plate at 160 ° C.) was 5 minutes, the solution was dehydrated and concentrated under reduced pressure. When the gelation time of the reaction product became 3 minutes, dehydration was performed. The concentration was stopped. The obtained final product was diluted with a mixed solvent of methanol 1: 1 and toluene 1 by weight to obtain a resin solid content of 5: 1.
A 0% secondary impregnation varnish was prepared. Kraft paper with a thickness of 0.2 mm and a basis weight of 135 g / m ² has an attached resin content of 18%
The primary impregnated varnish was impregnated and dried. Further, the secondary impregnation varnish was impregnated so that the total adhesion resin content with the adhesion resin content by the primary impregnation was 50%, and dried to obtain a prepreg. Eight pieces of this prepreg are stacked, and the tensile elongation at 180 ° C. is 5% on both outer surfaces.
Then, two sheets of electrolytic copper foil having a thickness of 35 μm were laminated and heated and pressed by a conventional method to obtain a double-sided copper-clad laminate having a thickness of 1.6 mm.

Example 2 A double-sided copper-clad laminate having a thickness of 1.6 mm was obtained in the same manner as in Example 1 except that an electrolytic copper foil having a tensile elongation at 180 ° C. of 10% and a thickness of 35 μm was used. Was.

Comparative Example A tensile elongation at 180 ° C. of 1.5% and a thickness of 35 μm
A 1.6 mm thick double-sided copper-clad laminate was obtained in the same manner as in Example 1 except that the electrolytic copper foil was used.

The obtained double-sided copper-clad laminate was subjected to JIS
Test pattern (D pattern, hole diameter 0.8 mm, 30 mm) specified in C 5012 (Printed wiring board test method)
), And a test piece was prepared by electrically connecting the front and back patterns with a silver paste, and a heat cycle test and a hot oil test were performed. Table 1 shows the results.

[0016]

[Table 1] Item Example 1 Example 2 Comparative Exampleヒ ー ト Heat cycle test (number of cycles) 300 345 100 Hot cycle test (number of cycles) 100 120 50 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

The details of the test method are as follows. Heat cycle test Maintained in air at 125 ° C for 30 minutes.
The number of cycles until disconnection is measured, with one cycle of holding in air at 5 ° C. for 30 minutes. Hot oil test After immersing in silicone oil at 260 ± 5 ° C for 5 seconds,
Immerse in 5 ° C water for 10 seconds, take out 5
One cycle of dipping for 10 seconds and draining for 10 seconds is defined as one cycle, and the number of cycles until disconnection is measured.

From Table 1, it can be seen that the number of cycles of the copper-clad laminate of the present invention is significantly larger than that of the copper-clad laminate of the comparative example.
It can be seen that the through-hole reliability is excellent.

[0019]

According to the present invention, a copper clad laminate having extremely high through-hole reliability can be obtained by using a copper foil having a tensile elongation at 180 ° C. of 3% or more.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H05K 1/09 H05K 1/09 A

Claims (1)

[Claims] 1. A copper-clad laminate obtained by attaching a copper foil having a tensile elongation at 180 ° C. of 3% or more to an insulating substrate made of a paper base material and a thermosetting resin.