JPH0222891A - Copper-clad laminated plate - Google Patents

Abstract

PURPOSE:To prevent occurrence of bending during a solder reflowing process at the time of surface mounting of components while punching workability is maintained so as to improve the dimensional stability by putting a sheet of copper foil to which a white bonding agent containing a specific quantity of titanium white is applied and dried on one surface of a sheet of prepreg and forming the copper foil and prepreg to one body with heat and pressure. CONSTITUTION:A sheet of copper foil to which a white bonding agent containing 3-40wt.% of titanium white is applied and dried is put on a sheet of prepreg and the titanium foil and prepreg are formed to one body by application of heat and pressure. It is preferable to use a base resin composed principally of a polyvinyl butyral resin of tiranium white, etc., as the white bonding agent and the base resin is used in a liquid state by dissolving the resin in a solvent. The copper foil with the bonding agent is prepared by applying the bonding agent so that the dried thickness of the bonding agent layer can become 15-40mum and drying the agent by heating. The prepreg is formed in a semihardened state by drying after impregnating a base material, such as kraft paper, etc., with a thermosetting resin. Since the copper-clad laminated plate formed to one body in such way have a white color and a high refrectivity against ultraviolet rays, far infrared rays, etc., the base plate formed of this laminated plate absorbs little heat and has no dimensional variation by bending.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a copper-clad laminate that does not warp and has excellent dimensional stability in a component surface mounting process.

(Conventional technology) In recent years, the development of electronic devices has been remarkable. Coupled with the rationalization and higher precision of processing technology for printed wiring boards, the mechanical properties required for the material copper-clad laminates have become increasingly strict. There is. In particular, copper-clad laminates that do not warp and have excellent dimensional stability are required due to surface mounting technology and line automation associated with higher wiring densities. The wiring board processing process that has a large effect on warpage and dimensional stability is the solder reflow process for component surface mounting.This process causes large warpage and dimensional changes, especially for paper-phenol boards that are versatile as printed wiring boards. There is a drawback.

(Problem to be solved by the invention) In the solder reflow process during surface mounting of components in the processing of printed wiring boards, the ideal is that only the solder is heated and melted by far infrared rays, and the board itself is heated by far infrared rays. In practice, it is quite difficult to avoid this effect, and the substrate itself is also subjected to extremely severe heat, which causes the substrate to warp and change dimensions. These improvements generally involve raising the glass transition point of the resin used for the substrate, but raising the glass transition point reduces the press punching properties of the substrate, such as when drilling holes and shaping the outside. There are drawbacks.

The present invention has been made in order to eliminate the above-mentioned drawbacks, and is a copper-clad laminate that does not warp during the solder reflow process during component surface mounting and has excellent dimensional stability while maintaining punching workability. This is what we are trying to provide.

[Structure of the Invention] (Means for Solving the Problems) As a result of extensive research to achieve the above object, the present inventor has developed a method that improves the viscosity of the adhesive without impairing the excellent punching workability. Based on this, we investigated the relationship between the hue of the board and its heat receiving capacity when irradiated with far infrared rays, and made sure that the areas where the copper foil was etched were white, making it difficult to absorb light. The present invention was completed based on the discovery that a copper-clad laminate with excellent dimensional stability without warping can be obtained by reducing the .

That is, the present invention uses a white adhesive containing 3 to 40% titanium white,
This copper-clad laminate is characterized in that copper foil coated with an adhesive, which has been applied and dried on copper foil, is superimposed on at least one side of a prepreg and formed into a heated and pressed body. Also, the white adhesive and adhesive-coated copper foil used in the copper-clad laminate.

The present invention will be explained in detail below.

The white adhesive used in the present invention can be made by dissolving titanium white together with a base resin in a solvent.

As titanium white, which is a component of the white adhesive, a wide variety of commercially available titanium whites can be used, and there are no particular restrictions. The blending ratio of titanium white is preferably 3 to 40% by weight based on the solid content of the base resin. If this ratio is less than 3% by weight, the heat receiving capacity increases, which is undesirable.

Moreover, if it exceeds 40% by weight, electrical properties and peel strength will deteriorate, which is not preferable. Although the white adhesive is one containing titanium white, other white fillers can be used in combination as necessary, as long as it does not contradict the purpose of the present invention. These white fillers include aluminum oxide, calcium carbonate, antimony oxide, talc, etc. Titanium white and other white fillers are treated with a coupling agent to improve surface wettability with the base resin. You can also do that.

The base resin that is a component of the white adhesive is not particularly limited, but polyvinyl butyral resin-phenol resin type, polyvinyl butyral resin-phenol resin type, and polyvinyl butyral resin-phenol resin type, which have an excellent balance of properties required as an adhesive for copper-clad laminates, are used. Base resins containing polyvinyl butyral resin as a main component, such as resin-epoxy resin system, polyvinyl butyral resin-melamine resin system, polyvinyl butyral resin-melamine resin-epoxy resin system, etc., are preferable, and these are dissolved in a solvent and used in the form of a solution. . The solvent for this adhesive can be used alone or in combination of two or more. The white adhesive can be easily produced by dissolving the above-mentioned base resin in a solvent, adding titanium white and other components, and mixing uniformly.

The adhesive-coated copper foil used in the present invention is prepared by coating a surface-treated copper foil with the white adhesive produced as described above so that the thickness of the adhesive layer after drying is 15 to 40 μm. death,
It is made by heating and drying. Copper foil for laminates is
It can be widely used regardless of whether it is electrolytic copper foil or rolled #4 foil.

The prepreg used in the present invention is produced by impregnating a base material with a thermosetting resin and drying it to a semi-cured state. Examples of the base material include kraft paper, linter paper, mixed paper thereof, glass cloth, glass vapor, polyamide nonwoven fabric, polynisdel nonwoven fabric, and the like. In addition, thermosetting resins include phenolic resin, epoxy resin,
Examples include unsaturated polyester resins and modified resins thereof, and these may be used alone or in a mixture of two or more. Although the present invention is not limited by the type of resin or base material that constitutes these pregregs, the effects of the present invention are most effectively exhibited when using phenolic resin copper based on paper. It is a tension laminate. The thus obtained white adhesive and the adhesive-coated copper foil coated with the white adhesive are laminated on at least one side of the prepreg and integrally formed under heat and pressure by a conventional method to produce a copper-clad laminate.

(Function) In the copper-clad laminate of the present invention, the adhesive layer has a white color due to the combination of titanium white. Therefore, the hue of the exposed parts other than the copper foil circuit formed by etching is white, and this increases the reflectance of ultraviolet rays, far infrared rays, and shade, so the board absorbs less heat, making it easier to use the solder reflow process using far infrared rays. Even after aging, the dimensional change due to warpage is small.

(Example of actual noodles) Next, the present invention will be explained by examples, but the present invention is not limited by these examples.

Example 1 A white adhesive was prepared by adding 15% by weight of titanium white in terms of solid content to a polyvinyl butyral resin-phenol resin-epoxy resin base resin solution and uniformly mixing. This adhesive was applied to copper foil without surface treatment using an applicator so that the adhesive thickness after drying was 25 μm, and after air drying, it was dried at 150 ° C. for 3 minutes to produce an adhesive-coated copper foil. .

This adhesive-coated copper foil was stacked on one side with eight sheets of paper-phenol laminate prepreg prepared separately so that the adhesive side was in contact with the foil, and was integrally formed under heat and pressure to produce a single-sided copper-clad laminate.

Example 2 A white adhesive was prepared by mixing 10% by weight of titanium white and 30% by weight of aluminum oxide in terms of solid content in a polyvinyl butyral resin-phenol resin epoxy resin base resin solution, and the same procedure as in Example 1 was made. Adhesive-coated copper foil and copper-clad laminates were manufactured.

Comparative Example 1 A polyvinyl butyral resin-phenolic resin-epoxy resin adhesive was applied to copper foil without surface treatment using an applicator so that the adhesive thickness after drying was 25 μl, and after air drying, it was heated at 150°C for 30 minutes. After drying for a minute, the adhesive formed a copper foil. This adhesive-coated copper foil is on a separate 2nd floor! The prepared eight sheets of paper-phenol laminate prepreg were stacked on one side so that the adhesive surfaces were in contact with each other, and the sheets were integrally formed under heat and pressure to produce a single-sided copper-clad laminate.

Comparative Example 2 The adhesive-coated copper foil produced in Comparative Example 1 was stacked on both sides of the prepreg of Comparative Example 1 so that the adhesive side was in contact with the prepreg, and the two were integrally formed under heat and pressure to produce a double-sided copper-clad laminate. .

In order to test the characteristics of the copper-clad laminates manufactured in Examples 1 and 2 and Comparative Examples 1 and 2, samples were cut into 300 x 250 nn, and an etching resist was applied to form a circuit on the copper foil surface. The copper foil other than the circuit was removed by etching. Afterwards, the etching resist was removed to create a circuit board. The adhesive surface exposed by etching is
The sample of Example had a white color, but the sample of Comparative Example had a brown color. These circuit boards were tested for warpage and dimensional shrinkage after passing through a far-infrared heating solder reflow process. These results are shown in Table 1, and the examples showed no warpage, excellent dimensional stability and punching workability, and the remarkable effects of the present invention were recognized.

Table 1 *1: The sample after the test was placed on a flat plate, and the maximum value of warpage was measured. The numerical value is expressed as the average value of 10 test samples.

*2: Drill holes in the four corners of the sample piece, and set the standard dimension between the holes to 3 vertically.
00 mm width 220111, and the dimensional shrinkage rate after passing through a solder reflow device was measured.

The numerical value is expressed as the average value of 10 test samples.

[Effects of the Invention] As is clear from the above explanation and Table 1, the copper-clad laminate of the present invention maintains excellent punching workability and does not cause warping even during the solder reflow process during component surface mounting. It had excellent dimensional stability.

Claims (1)

[Scope of Claims] 1 A white adhesive containing 3 to 40% by weight of titanium white is coated on a copper foil and dried, and the adhesive-coated copper foil is overlaid on at least one side of a prepreg, and the adhesive-coated copper foil is integrally formed by heating and pressing. A copper-clad laminate that is characterized by: 2. A white adhesive for copper-clad laminates, comprising a base resin and 3 to 40% by weight of titanium white based on the solid content of the base resin. 3. Copper foil with adhesive, characterized in that it is made by applying and drying a white adhesive containing 3 to 40% by weight of titanium white onto copper foil.