JPS6143559A - Laminated board for chemical plating - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention provides a smooth adhesive layer for chemical plating to improve the printability of resist ink, the adhesion of the plating layer, the reliability of solder heat resistance, etc. This is a dispute regarding a method of manufacturing laminates for chemical plating, which aims to improve the quality of chemical plating.

[Conventional technology]

As a method for manufacturing printed wiring boards, the subtractive method, in which circuits are formed by etching unnecessary parts of copper-clad laminates, has been widely used.

However, in recent years, as the size and weight of electronic devices have become smaller and lighter, as well as advances in mounting components, the requirements for conductor width and conductor spacing in printed circuits have become even stricter. Subtractive methods can no longer meet these requirements, and chemical plating As a result, additive methods for forming circuits have come into the spotlight. This method of manufacturing printed wiring, called the additive method, adds and forms conductive patterns only at the necessary locations on the laminate, and the current main production method involves applying resist ink in a reverse pattern onto the laminate. Then, a conductor circuit is formed in the necessary circuit pattern portion by chemical plating or a combination of chemical plating and electroplating.

In such additive methods, various proposals have been made regarding chemical plating methods and substrates to be plated.In particular, regarding substrates, an adhesive layer is provided on the surface of the laminate, and this adhesive layer has good chemical resistance. The rubber component in the adhesive is chemically eluted by treatment with an oxidizing agent and the surface is roughened, and this is then chemically plated. It is common to try to increase the adhesion strength of the plating layer by applying.

The following three methods can be cited as representative methods for manufacturing laminates suitable for the additive method.

Namely, (1) a method in which a chemical plating adhesive is applied to the surface of the laminate to a certain thickness by dipping or curtain coating, and then dried and hardened.

■ Layer the desired number of prepregs impregnated with thermosetting resin, layer the release film so that the surface of the prepreg is in close contact with the adhesive layer for chemical plating formed on one side of the release film, and heat them. A method of forming while applying pressure.

■ A method in which the release film is stacked on the surface of the laminate so that the adhesive layer for chemical plating formed on one side of the release film is in close contact with the surface of the laminate, and the product is formed while being heated and pressurized.

It is. Note that the adhesive layer for chemical plating formed on the release films of (1) and (2) was coated to a uniform thickness of 1 using a bar coater or the like.

Here, in the method (2), the surface of the adhesive layer for chemical plating does not become smooth, the precision of resist printing decreases, and the precision of the conductor circuit formed by chemical plating deteriorates. In addition, although the surface smoothness of the adhesive layer for chemical plating is good in method (2), the adhesive gets mixed into the prepreg during heating and pressure molding, making the effective thickness of the adhesive layer for chemical plating uneven, and the surface As a result, the roughening state of the plating circuit is not constant, resulting in poor adhesion (beer strength) and heat resistance (soldering heat resistance) of the plating circuit.
Variations will appear. Furthermore, method (2) can be said to be a preferable method in terms of the smoothness of the surface of the adhesive layer for chemical plating, the prevention of the adhesive from mixing into the prepreg, and the resulting uniformity of the thickness of the adhesive layer for chemical plating. Since heating and pressure molding is required twice, productivity decreases and manufacturing costs increase.

[Problems to be solved by the invention] 1
As mentioned above, in the conventional technology regarding laminates for chemical plating, the surface smoothness of the adhesive layer for chemical plating provided on the surface of the laminate, and the thickness of the adhesive layer due to the mixing of the adhesive into the prepreg, There was a problem that none of them were satisfactory in terms of variation and productivity.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention provides a layer with a density of 0 on the surface layer of a laminate on which a chemical plating adhesive layer is to be provided.
．． Using a prepreg based on high-density base paper of 5 to 0.9 g 7 cm3 and thickness 1 to IQ nil, an adhesive layer for chemical plating is further provided on the surface of this prepreg, and these are simultaneously heated and pressure molded. The method of doing so was adopted.

[Effect]

First, the type of prepreg used in the present invention is not particularly limited, but examples of currently widely used prepregs include low-density kraft paper or linter paper with a density of less than 0.45 g/cm. 30-7 on paper like
The low molecular weight resin to be impregnated with 0% is diluted with a solvent to a viscosity with good impregnating properties (called varnish), the base material is impregnated with this solution, the solvent is evaporated off by heating, and at the same time the molecular weight of the resin is adjusted to room temperature. At the bottom, it is solid and has no fluidity, but it has been increased to a state where it becomes fluid when heated (B stage). Therefore, in normal cases, even if the voids of the base material are completely impregnated and filled with varnish, the base material in the B stage will still have voids due to the volatilized solvent.
The apparent cross-sectional area of the base material is approximately 15-2
0% by volume) remains. When manufacturing normal laminates, these voids are filled with prepreg resin that has been given fluidity by heating and pressurizing, so that void-based failures do not occur, but when the chemical plating adhesive layer is applied to the prepreg surface. (In this case, when manufacturing a laminate plate provided in the B stage, the adhesive on the prepreg surface with voids is drawn into the voids, similar to the prepreg resin that has become fluid due to heat and pressure, and forms an adhesive layer.) Therefore, it is recommended to use prepreg based on high-density kraft paper or high-density linter paper with few voids on the surface layer of the laminate on which the adhesive layer for chemical plating is to be applied. If used, there will be no thickness variation in the chemical plating adhesive layer provided afterwards.

〔Example〕

The resin content of the prepreg is usually 30 to 70%, preferably 40 to 60%, depending on the characteristics of the laminate to be obtained and the molding conditions involved. The high-density kraft paper or linter paper used as the prepreg base material for the surface layer of the laminate on which the adhesive layer for chemical plating is to be applied is paper that has been passed through a group of drying cylinders under high pressure after papermaking. Because of this, the fibers (the fibers of linter paper are longer than those of kraft paper) are closely spaced, and there are fewer voids than normal paper, and the density is 0.5 to 0.9 g/crn3 (substantially 0. .45
~0.94 g/cm3). If the paper has a density within this range, the varnish can easily penetrate into the gaps between the fibers by capillary action, and a prepreg with few voids (hereinafter referred to as special prepreg) can be obtained. If the paper quality exceeds 0.94 g/Cm3, the varnish impregnation will be insufficient, making it impossible to obtain a laminate with the necessary properties;
Paper materials with a low density of less than /cm3 are equivalent to conventional prepregs, and even if an adhesive layer for chemical plating is attempted to be provided, a uniform thickness cannot be obtained.

The specific method of providing the chemical plating adhesive layer on the surface layer of the special prepreg is, for example, on the surface of a film-like base material such as release paper (this method is applied in advance and transferred to the surface of the special prepreg). There is no problem whether it is applied directly to the special prepreg surface, or if it is applied directly to the special prepreg surface.
Furthermore, the number of special prepregs is not limited to one for a set of prepregs (it is also possible to use multiple sheets), and it is possible to stack multiple sheets of normal prepreg, layer the special prepreg on top of that, and then layer the special prepreg on top of that surface. In order to apply an adhesive layer for chemical plating and heat and pressure mold them all at once, it is necessary to pass them continuously through heated rolls that are adjusted to an appropriate feeding speed and temperature, or to adjust the temperature and time. If the adhesive layer for chemical plating provided on the surface of the special prepreg is applied directly, it may be necessary to use a heated press such as a heating roll or press to prevent the surface from melting. It goes without saying that it is preferable to apply heat and pressure through a paper pattern.

Example 1: Carboxylated NBR (manufactured by Nippon Zeon Co., Ltd.: N1pol) was used as an adhesive varnish for chemical plating.
-1072) ・・・・・・・・・ 5
0 parts by weight epoxy resin (manufactured by Asahi Kasei Corporation: AER-661)
......50/l Phenol resin (manufactured by Bessatsu Kogyo Co., Ltd.).

・・・・・・・・・ 10/l Diaminodiphenylsulfone (DDS)・・・・・・・
・・・ 5 tt2-ethyl, 4-methylimidazole (2E4MZ) ・・・・・・・・・
0.3I/silicon dioxide ・・・・・・・・・
・・・ 10 ・I solvent (MEK) ・・
Prepare a mixture consisting of 450 =
This was applied onto a 50 μm thick stretched polypropylene film using a reverse coater and dried at 100° C. for 10 minutes to produce a release film with a 40 μm thick adhesive layer for chemical plating. On the other hand, an oil-modified phenolic resin varnish prepared using methanol and toluene to have a solid content of 55% was prepared with a thickness of 7 ml and a density of 0. B2 g/cm3
The composition was applied to high-density kraft paper so that the resin content after drying was 50% and the flow value was 10%, and then dried to remove the solvent. The porosity of the special prepreg thus obtained was 5%. Therefore, we combined five sheets of conventional prepreg made of paper phenolic resin, overlaid the special prepreg on each of the front and back surfaces, and then chemically plated the previously prepared release film on top of the special prepreg. 100 kgf/cm, 165℃, 6
They were heated and pressurized all at once under conditions of 0 minutes to perform integral molding. After molding, the release film is peeled off from the surface of the laminate, and the uniformity of the adhesive layer and the surface roughness (10-point average roughness μm) are measured. After that, a printed wiring board is manufactured by the usual additive method, and the JIS -C6481, various properties such as peel strength (kgf/cm) and soldering heat resistance (number of seconds at 260°C) were investigated, and the results are summarized in a table.

Example 2: The oil-modified phenolic resin varnish used in Table Example 1 was applied to high-density linter paper with a thickness of 10 mil and a density of 0.50 g/Cm3 so that the resin content after drying was 60% and the flow value was 10%. After coating as described above, it was dried to produce a special prepreg (porosity: 6%). A printed wiring board was produced by combining this special prepreg in exactly the same manner as in Example 1, and various properties were measured.The results obtained are also listed in the table.

Comparative Example 1: Instead of special prepreg, ordinary paper phenol prepreg (base paper has a thickness of IQ mil and a density of 0°44 g/cm3)
A printed wiring board was prepared in exactly the same manner as in Example 1, except that kraft paper) was used, and various properties were measured. The obtained results are also listed in the table. As is clear from the table, the interface between the adhesive layer for chemical plating and the left side of the normal prepreg is heavily mixed with each other, and the thickness varies greatly from 0 to 20 μm, and even though the surface is smooth, it is not uniform. is defective;
Both peel strength and solder heat resistance were low.

Comparative Example 2: Instead of special prepreg, ordinary paper phenol prepreg (base paper has a thickness of 10 mil and a density of 0.44 g/cm)
A printed wiring board was prepared in the same manner as in Example 1, except that linter paper (No. 3) was used, and various properties were measured. The performance was significantly inferior, and like Comparative Example 1, it was unfavorable.

Comparative Example 3: 7 sheets of regular paper phenol prepreg stacked, 100k
gE/cm2. A paper phenol laminate was obtained by heating and pressing at 165°C for 10 minutes. This laminate was immersed in the same chemical plating adhesive face solution used in Example 1, pulled out in the vertical direction at a speed of 6 m/min, pre-dried at 100°C for 10 minutes, and then heated at 165°C for approx. It was dried for 1 hour. A printed circuit board was fabricated from this laminate using the usual additive method, and the same properties as in the examples were investigated, and the results were also listed in the table. The layer thickness varied greatly, the uniformity was extremely poor, and the surface roughness of the circuit board was as large as 4 to 10 μm, and the peel strength and soldering heat resistance were far inferior to any of the examples.

〔effect〕

The chemical plating laminate of this invention minimizes mixing of chemical plating adhesive and special prepreg resin,
A layer of uniform thickness is formed without causing any disturbance in the thickness or composition of the adhesive layer for chemical plating. Furthermore, when applying such an adhesive layer for chemical plating, if a transfer method is used on the prepreg surface, productivity will be improved, the surface smoothness of the adhesive layer will be excellent, printability, adhesion of chemical plating, Since the solder heat resistance is greatly improved and the reliability is significantly increased, it can be said that the chemical plating laminate of the present invention is of great significance.

Claims (1)

[Claims] A prepreg based on base paper with a density of 0.5 to 0.9 g/cm^3 and a thickness of 1 to 10 mil is used for the surface layer of the laminate, and an adhesive for chemical plating is further provided on the surface of this prepreg, A laminate for chemical plating that is characterized by being formed by heating and pressurizing these at the same time.