JPH0243352B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a copper-clad laminate with less warpage by using a specific kraft base paper.

Paper-based phenolic resin copper-clad laminates or epoxy resin laminates are relatively inexpensive and are therefore used in large quantities in consumer electronic devices. In particular, recently, the processing methods for printed circuit boards have diversified, and the automation and labor-saving of processing lines are being actively investigated. requested.

Many reports have been made regarding the improvement of the warping behavior of conventional copper-clad laminates, which can be broadly classified into the following two types.

(1) Reduce the amount of change in warpage - Use kraft pulp paper, which has a low shrinkage rate, as the base paper used for copper-clad laminates. (Japanese Unexamined Patent Publication No. 51-73579) (2) Adjust the warpage behavior to suit the processing line - use linter paper, mixed paper, etc. with a high shrinkage rate under the copper foil, and use other paper with a low shrinkage rate. Using kraft paper, the warp level is shifted to a flat direction with a bimetallic effect. (Jitsukai 53-
117584, etc.) Regarding (1), there is a problem that the warpage level cannot be changed because it is only made of kraft paper, and regarding (2), there is a problem that the warp level cannot be changed due to the intense heating of one side such as irradiation with far-infrared lamps on the copper foil side in the processing line. , there is a problem with warping that has the opposite effect.

The present invention has been made to eliminate these drawbacks. In other words, the present invention focuses on the castor oil penetration ratio of the front and back sides [back (wire side)/front (felt side)].
A predetermined number of processed papers obtained by impregnating kraft paper with a coefficient of 1.5 or higher with phenolic resin or epoxy resin and drying them by heating are stacked face up (felt side), and then copper foil is applied on top of the paper and heated and pressed. The present invention provides a method for manufacturing a copper-clad laminate with less oxidation.

The present invention will be explained in detail below.

The kraft base paper used in the present invention is a kraft base paper in which the castor oil permeability ratio between the front and back surfaces is 1.5 or more. Here, the front side of the kraft paper is the felt side,
The back side is the wire side. Castor oil penetration is viscosity
Castor oil, which has the characteristics of 6.5±0.3 (25℃), specific gravity 0.945±0.006 (25℃), and refractive index 1.479±0.001 (25℃), is kept at a constant temperature of 30±5℃, horizontally to the liquid surface, According to JIS P-8110 “Test paper collection method”,
It is the number of seconds it takes for castor oil to permeate the entire surface of a 1-inch diameter circular sample that has been subjected to JIS P-8111 ``Pretreatment of test paper''.

There is no effect if the castor oil penetration ratio is less than 1.5.

The phenolic resin used in the present invention includes phenol, cresol, butylphenol, octylphenol, nonylphenol, or a mixture thereof synthesized using formalin, paraformaldehyde, etc. and an amine catalyst according to a conventional method;
Alternatively, it is an oil-modified phenolic resin made by reacting phenols and tung oil under acidic conditions, and then synthesizing formalin, paraformaldehyde, etc. using an amine catalyst. A flame-retardant phenolic resin containing a flame retardant or a nitrogen-based flame retardant.

Examples of epoxy resins include bisphenol epoxy resins and flame-retardant epoxy resins made by adding chlorendecic anhydride to bisphenol brominated epoxy resins and adding brominated flame retardants such as tetrabromobisphenol A or tetrabromodiphenyl ether. Can be mentioned.

In order to manufacture copper-clad laminates using processed paper that is made by impregnating kraft paper with such a resin and drying it by heating,
It is a conventional method to stack a predetermined number of processed papers with the front side (felt side) facing up, apply copper foil on top, and heat and pressurize.

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

Example 1 Using 10 mils Kraft base paper (castor oil penetration ratio 1.58), the front (felt side) had a castor oil penetration of 12 seconds and the back (wire side) had a castor oil penetration of 19 seconds.
This is coated and impregnated with an oil-modified phenolic resin as shown below to obtain processed paper.

Examples of oil-modified phenol varnishes include 250 parts of phenol, 340 parts of cresol, and nonylphenol.
300 parts of tung oil, 350 parts of tung oil, and 720 parts of 37% formalin were added, monomethylamine was added to adjust the pH to 6, and the mixture was reacted at 100°C for 3 hours. After that, it was dehydrated under reduced pressure and diluted with a mixed solvent of toluene/methanol = 7/3, resulting in a resin solid content of 55% by weight and a viscosity of
2.3 poise (25℃), gelation time 2 minutes 10 seconds (150℃)
The following was used.

Eight sheets of processed paper were stacked with the front side facing up, and adhesive-coated copper foil was layered on top of that, followed by heating and pressure molding at 170℃ and 150Kg/cm ² to obtain a phenolic copper-clad laminate. .

Example 2 The same kraft paper used in Example 1 was pre-impregnated with water-soluble phenol varnish and then coated and impregnated with the following epoxy resin to obtain processed paper.

The epoxy resin used here includes 100 parts of epoxy resin (bisphenol A type epoxy resin: epoxy equivalent: 500) and 35 parts of hexyl anhydride.
An epoxy varnish with a 60% non-volatile content was used in a solvent such as acetone or methyl ethyl ketone.

Eight sheets of this prepreg were piled up, and an adhesive-coated copper foil was placed on top of the prepregs, followed by heat and pressure molding at 150° C. and 100 kg/cm ² to obtain an epoxy copper-clad laminate.

Comparative Example 1 The same oil-modified phenolic resin as in Example 1 was applied to a general 10 mils Kraft base paper (castor oil penetration ratio 1.2) with a castor oil penetration rate of 15 seconds on the front side and a castor oil penetration rate of 18 seconds on the back side. Processed paper was obtained by impregnation, and the processed paper was treated in the same manner as in Example 1 to obtain a phenolic copper-clad laminate.

FIG. 1 shows the state of warpage in the subsequent processing steps for the phenolic copper-clad laminates of Example 1 and Comparative Example 1. The warpage was measured as shown in FIG.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the state of warpage of a phenolic copper-clad laminate in each process, and FIG. 2 shows a method for measuring warpage. 1...Copper-clad laminate, 2...Copper foil.

Claims (1)

[Claims] 1. Castor oil permeability ratio of front and back [back (wire side)/
Kraft paper with a surface (felt side) of 1.5 or higher is impregnated with phenolic resin or epoxy resin.
A method for producing a copper-clad laminate with little warping, which comprises stacking a predetermined number of processed papers obtained by heating and drying with the front side (felt side) facing up, applying copper foil thereon, and heating and pressing.