JP3100689B2 - Method of forming recess for mounting electronic components on printed wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a concave portion for mounting an electronic component on a printed wiring board.

[0002]

2. Description of the Related Art Conventionally, an IC chip has generally been housed in a package such as a dual in-line package and mounted on a printed wiring board. A package can be mounted on a printed wiring board by inserting a large number of leads (pins) provided in the package into through holes in the printed wiring board and soldering, or by connecting the leads to the printed wiring board like a flat package. There is a method of directly soldering to the pad portion of the conductor pattern without inserting it into the through hole. Then, in order to reduce the thickness of the device and improve the packaging density, a concave portion is formed in the printed wiring board, and the IC chip or IC package containing the concave portion is formed therein.
A method of arranging external chip components such as a capacitor and a resistor for setting the operating condition of C has also been performed.

Conventionally, recesses for mounting electronic components such as IC chips have been formed by the procedure shown in FIG. That is, a hole 24 for a through hole is first made in a substrate 23 in which a copper foil 22 is laminated on both sides of a base material 21 (FIG. 4B), and then a concave portion 25 is formed by sitting (gouging) at a predetermined position. After forming and honing (FIG. 4C), a plating process including at least electroless plating and pattern formation are performed (FIG. 4D).

[0004]

However, in the conventional method, only the unevenness due to the honing process is present on the surface of the concave portion 25 on which the electroless plating process is performed. Poor adhesion to 21
When the electronic component is mounted in the concave portion 25, the plating layer 26 may peel off from the base material 21, and there is a problem that the reliability of the printed wiring board is low. It is conceivable to apply an adhesive for electroless plating for an additive printed wiring board on the surface of the concave portion 25 to form an adhesive layer, and to roughen the surface to improve the adhesion to the plating layer 26. 2
It is very difficult to apply the adhesive with a predetermined thickness only to the surface of the concave portion 25 after the formation of the step 5, and if it is performed on a production line, the operation efficiency will be greatly reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object to improve the adhesion to a plating layer formed in a concave portion in which an electronic component is mounted and to provide a state in which the electronic component is mounted. It is an object of the present invention to provide a method for forming a concave portion for mounting an electronic component on a printed wiring board, which can reliably prevent the plating layer from peeling off and improve the reliability of the printed wiring board.

[0006]

In order to achieve the above object, in the present invention, an adhesive layer is formed by applying an electroless plating adhesive to at least a portion of a substrate surface where a concave portion is to be formed. An insulating material layer coated with the adhesive is formed on at least the surface portion except for a predetermined portion where a concave portion is to be formed, and then the surfaces of the adhesive layer and the insulating material layer are roughened. Electroplating was performed.

[0007]

After an adhesive is applied to at least a portion of the base material surface where a concave portion is to be formed to form an adhesive layer, an insulating material layer is formed in a portion other than a predetermined portion where a concave portion is to be formed. The insulating material layer is formed entirely of an adhesive or formed by laminating a prepreg and applying the adhesive to a surface portion thereof. Next, after the surfaces of the adhesive layer and the insulating material layer are roughened, electroless plating is performed. The plating layer is not formed directly on the surface of the base material, but is formed on the roughened adhesive layer with a surface having a large anchor effect, so that the adhesion is improved.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will now be described with reference to FIGS.
This will be described with reference to FIG. 40 parts by weight of a bisphenol A type epoxy resin (manufactured by Yuka Shell, trade name: E-1001), 60 parts by weight of a phenol novolak type epoxy resin (manufactured by Yuka Shell, trade name: E-154), and an imidazole type curing agent 5 parts by weight (manufactured by Shikoku Chemicals, trade name: 2PHZ), 10 parts by weight of epoxy resin fine particles (manufactured by Toray, trade name: Trepearl EP-B, average particle size: 0.5 μm), and epoxy resin fine particles (manufactured by Toray, product: Name: Trepal EP-B,
25 parts by weight of an average particle size (5.5 μm) and 75 parts by weight of butyl cellosolve acetate were stirred and mixed with a three-roller to prepare an adhesive for an additive printed wiring board (hereinafter, simply referred to as an adhesive).

The adhesive was applied to both surfaces of the substrate 1 with a roll coater to a thickness of 30 μm to form a first adhesive layer 2a (FIG. 1). Then, the adhesive is applied by screen printing to a portion of the base material 1 on which the first adhesive layer 2a is formed except for a predetermined portion where the concave portion 3 is to be formed, and a second material as an insulating material layer is applied. An adhesive layer 2b was formed (FIG. 2
(A)). The application of the adhesive is divided into two steps, and one
Coated to a thickness of 00 μm, 200 μm by two coatings
And the thickness. Next, both adhesive layers 2a and 2b are heated and dried and cured, and then immersed in a chromic acid aqueous solution (800 g / l) at 70 ° C. for 1 hour.
The surfaces of the adhesive layers 2a and 2b were roughened by immersion for 0 minutes. Next, drilling for through holes was performed (FIG. 2).
(B)) After that, a plating resist layer 4 is formed at a predetermined position (FIG. 3A), and electroless copper plating is performed under normal conditions.
A copper plating layer 5 was formed on a portion not covered with the plating resist layer 4 (FIG. 3B).

The entire surface of the concave portion 3 is formed by the adhesive layers 2a and 2b. The roughening treatment with the chromic acid aqueous solution provides a large anchor effect, and the adhesiveness with the copper plating layer 5 is good. . The adhesion strength of the copper plating layer 5 formed in the recess 3 is the same as the adhesion strength of the copper plating layer 5 formed in a portion other than the recess 3, and the peel strength is 1.
It was 7 kg / cm. Then, even when an electronic component was mounted in the recess 3, the copper plating layer 5 did not peel off.

The present invention is not limited to the above embodiment. For example, instead of forming the second adhesive layer 2b constituting the insulating material layer by applying a liquid adhesive, the present invention is not limited thereto. May be formed into a dry film to form a sheet having a predetermined thickness, and a sheet obtained by punching out a portion to be the concave portion 3 may be laminated on the first adhesive layer 2a.
Also, instead of forming the entire insulating material layer with an adhesive, a semi-cured prepreg formed by impregnating a glass cloth with an epoxy resin to have a predetermined thickness and punching a hole serving as a concave portion 3 is a first prepreg. The adhesive may be laminated on the adhesive layer 2a, and the surface of the adhesive may be coated with the adhesive to a thickness of 30 μm to form an adhesive layer. Further, an adhesive for an additive printed wiring board other than the above may be used as the adhesive, or the first adhesive layer 2a may be applied only to the portion where the concave portion 3 is to be formed instead of applying to the entire surface of the substrate 1. .

[0012]

As described above in detail, according to the present invention, at least the bottom surface of the concave portion is formed of an adhesive layer and roughened, and electroless plating is performed. As a result, the peeling of the plating layer when the electronic component is mounted is reliably prevented, and the reliability of the printed wiring board is improved.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a substrate of the present invention and a state where a first adhesive layer is formed on the entire surface thereof.

2A is a schematic sectional view showing a state in which a second adhesive layer is formed, and FIG. 2B is a schematic sectional view showing a state in which the surface of the adhesive layer is roughened and a hole is formed in a base material.

3A is a schematic cross-sectional view showing a state where a plating resist layer is formed, and FIG. 3B is a schematic cross-sectional view showing a state where electroless plating is performed.

FIG. 4 is a schematic sectional view showing a procedure for forming a conventional concave portion.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Base material, 2a ... First adhesive layer, 2b ... Second adhesive layer as insulating material layer, 3 ... Concave part, 4 ... Plating resist layer, 5
... copper plating layer.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H05K 3/10-3/38

Claims (1)

(57) [Claims] An adhesive for electroless plating is applied to at least a portion of a surface of a substrate (1) where a recess is to be formed to form an adhesive layer (2a), and then a predetermined portion to form a recess (3) is formed. An insulating material layer (2b) coated with the adhesive is formed on at least the surface of the portion except for the portion, and then the surfaces of the adhesive layer (2a) and the insulating material layer (2b) are roughened. Forming a concave portion for mounting an electronic component on an additive printed wiring board by electroless plating.