JP2720853B2 - Manufacturing method of printed wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a printed wiring board, and more particularly to a method for manufacturing a printed wiring board having through holes.

[0002]

2. Description of the Related Art As electronic devices have become smaller, lighter, have higher performance, have higher speed, and have lower prices, printed wiring boards have also been required to have higher density wiring and lower cost.

One of the conventional methods for manufacturing a printed wiring board for satisfying these requirements is a through-hole-filled substrate. This is a method in which a conductive paste is buried in a hole after drilling a hole in a copper-clad laminate, and has an advantage that landless formation (no land) is possible.

However, there is a problem that the connection reliability is not sufficient in the above conventional method.

To solve this problem, for example, Japanese Unexamined Patent Publication (Kokai) No. 62-193197 discloses that a conductor pattern is formed on both front and back surfaces, and a through hole for connecting both surfaces and a through hole for mounting components are both provided. In manufacturing a printed wiring board having, first, a hole for double-sided connection is drilled at a predetermined position of the copper-clad laminate, and the double-sided connection hole is filled with a conductive paste. There has been proposed a method of manufacturing a through-hole printed wiring board in which copper plating is applied to the entirety after being provided, and then unnecessary portions are removed by etching to form a conductor pattern.

A method for manufacturing a printed wiring board described in the above-mentioned Japanese Patent Application Laid-Open No. 62-193197 will be described below in detail with reference to the drawings. 3 (a) to 3 (e) are cross-sectional views showing a method of manufacturing a printed wiring board described in Japanese Patent Application Laid-Open No. 62-193197 in the order of steps.

According to the method described in JP-A-62-193197, a printed wiring board having conductor patterns formed on both front and back surfaces and having both through-holes for connecting both sides and through-holes for inserting mounting components is manufactured. First, a copper-clad laminate 1 in which both surfaces of an insulating substrate 1-2 are covered with a copper foil 1-1 is prepared (see FIG. 3A), and both sides are connected to a predetermined position of the copper-clad laminate 1. Holes (Fig. 3
(B)), the conductive paste 2 is filled into the holes for both-side connection (see FIG. 3 (c)), and after the holes for inserting the mounted components are provided, the whole is plated with copper (3). FIG.
Then, unnecessary portions are dissolved and removed by etching to form a conductor pattern (see FIG. 3E).

[0008]

However, in the method of manufacturing a printed wiring board described in Japanese Patent Application Laid-Open No. 62-193197, the connection between the conductive paste and the outer conductor pattern is completed. In addition, copper plating is required, which results in an increase in the thickness of the outer copper body, which limits the formation of a fine pattern (fine pattern).

For example, when a 20 μm plating (copper plating) is applied to a 35 μm copper foil, the overall copper thickness becomes 55 μm, and the yield of 50 μm / 50 μm in circuit width / circuit gap (ie, conductor pattern width / conductor gap) is as follows. About 20-30%
It is as follows.

Further, in the method of manufacturing a printed wiring board described in Japanese Patent Application Laid-Open No. Sho 62-193197, copper plating is required, and equipment and man-hours for the plating are required.

Accordingly, it is an object of the present invention to provide a method of manufacturing a printed wiring board which solves the above-mentioned problems of the prior art, improves connection reliability, and enables inexpensive and high-density wiring.

[0012]

According to the present invention, there is provided a copper-clad laminate, comprising the steps of: preparing a copper-clad laminate; drilling a hole at a desired position; burying a conductive paste at a location of the holes were then forming a conductive pattern by dissolving and removing unnecessary portions by etching, Mu then selectively substituted in the embedded hole surface with a conductive paste of the conductor pattern The method includes a step of forming a solder layer by electrolytic plating and a step of fusing the solder layer.

[0013]

In the present invention, since the outer layer is not plated with copper, the thickness of the copper body is thin and a fine pattern can be formed. A connection with the conductor pattern is obtained by selectively forming a solder layer thereon and fusing, so that the connection reliability of both surfaces is ensured.

In the present invention, a paste such as copper or silver is preferably used as the conductive paste.

As a method of forming a solder layer,
Preferably, substitution type electroless solder plating is used. By using the substitution type electroless solder plating, the conductive paste on the copper surface of the hole land and the hole surface is replaced with a solder layer,
By fusing, the hole land and the solder layer on the hole surface are integrated, and connection reliability is improved.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1A to 1F show a first embodiment of the present invention.
FIG. 7 is a cross-sectional view illustrating a method of manufacturing a printed wiring board according to the embodiment in the order of steps.

First, a copper foil thickness of 9 to 35 μm and a plate thickness of 0.1 to
A 1.6 mm copper-clad laminate 1 is prepared (see FIG. 1 (a)), and a hole having a drill diameter of 0.1 to 1.0 mm is formed in a desired location by a predetermined N / C drilling machine (see FIG. 1). 1 (b)),
A mask that can be coated with a conductive paste 2 such as copper or silver at a desired position is prepared in advance, and the conductive paste 2 is buried in a hole portion formed by a screen printing machine using the mask. After drying at a temperature, the surface is polished and smoothed with a belt sander or a buffing machine (see FIG. 1 (c)).

The method of embedding the conductive paste in the holes is as follows.
A method such as a roll coater other than screen printing may be used.

Next, after an etching resist is applied by a photographic method or a screen printing method, as shown in FIG. 1D, an unnecessary portion of the copper foil is dissolved and removed by etching to form a conductor pattern 6. The etching resist is stripped.

As the etching method, a conveyor device is used, and a copper chloride solution or an iron chloride solution is used.
The treatment is performed at a temperature of 60 ° C. for about 1 to 3 minutes.

Next, after performing a pretreatment of degreasing and soft etching, an electroless solder plating process is performed, and 3 to 2 are applied to the surface of the conductive pattern 6 and the conductive paste 2 and the land.
A solder plating having a thickness of 0 μm is deposited to form a solder layer 4 (see FIG. 1E).

Next, the printed wiring board is obtained by fusing (fusing) to secure the connection between the conductive paste 2 and the land (see FIG. 1 (f)).

In this embodiment, since the thickness of the copper body is only the thickness of the copper foil, a circuit width / gap width of 50/50 μm can be easily formed.

In the present embodiment, after the fusing step, a desired portion may be covered with a solder resist (not shown) to form a printed wiring board.

FIGS. 2A to 2G are sectional views showing a method of manufacturing a printed wiring board according to a second embodiment of the present invention in the order of steps.

In this embodiment, the materials used and common steps are performed in the same manner as in the first embodiment. First, a copper-clad laminate 1 is prepared (see FIG. 2A), and N / C
Holes are drilled by a drilling machine (see FIG. 2 (b)), a mask is formed in advance to allow the conductive paste 2 to be applied to a desired location, and using this, a portion of the hole drilled by a screen printing machine is used. Then, the conductive paste 2 is embedded in the substrate, and the surface is polished and smoothed (see FIG. 2C).

Next, after an etching resist is applied by a photographic method or a screen printing method, an unnecessary portion of the copper foil is dissolved and removed by etching as shown in FIG. Is peeled off.

Next, a pad portion (not shown) for mounting the mounted component, a hole filled with the conductive paste 2 and a solder resist 5 having its land portion removed like a window are formed (FIG. 2).
(See (e)), and then a pretreatment of electroless solder plating and an electroless solder plating process are performed to deposit solder plating on the pad portion, the conductive paste 2 and the land, thereby forming a solder layer 4 (FIG. 2). (F)).

Next, the connection between the conductive paste 2 and the land is secured by fusing (FIG. 2).
(G)), thereby producing a printed wiring board. As described above, in this embodiment, the printed wiring board is manufactured by selectively supplying the solder by electroless plating only to the portion requiring solder, that is, the portion in which the conductive paste 2 is embedded and the pad portion. doing.

With respect to the formation of a fine pattern, in the prior art, for example, when a 20 μm plating is applied to a 35 μm copper foil, the entire copper body thickness becomes 55 μm, and the circuit width / circuit gap is 5 μm.
While the yield of 0 μm / 50 μm is, for example, about 20 to 30% or less, in the present embodiment, the copper foil thickness is 35 μm.
m, resulting in the same circuit width / circuit gap (50 μm).
m / 50 μm), a yield of about 70-80% was obtained.

[0032]

As described above, in order to obtain the connection reliability between the conductive pattern and the filled conductive paste,
Whereas in the prior art, copper plating is performed, whereas in the method for manufacturing a printed wiring board according to the present invention, a solder layer is formed by electroless solder plating, and connection reliability is secured by fusing. Therefore, the thickness of the surface conductor can be reduced, a fine pattern can be formed, and equipment and man-hours for catalyst treatment and copper plating treatment are not required, and an effect of obtaining a high-density wiring and an inexpensive printed wiring board can be obtained. is there.

With respect to the fine pattern formability, in the prior art, for example, when a 35 .mu.m copper foil is plated with 20 .mu.m, the total copper body thickness becomes 55 .mu.m, and the yield of 50 .mu.m / 50 .mu.m in circuit width / circuit gap becomes 20 to 30% or less. In contrast, the present invention has an effect that the copper foil thickness is only 35 μm and the yield reaches about 70 to 80% with the same circuit width / circuit gap.

The copper plating process is generally performed by
Degreasing, soft etching, catalyst application, electroless copper plating,
Electroless copper plating will be used, but the electroless solder plating process will be degreasing, soft etching, and electroless solder plating. According to the present invention, the number of steps can be reduced, thus reducing equipment costs and man-hours. It has the effect that can be done.

[Brief description of the drawings]

FIG. 1 is a sectional view illustrating a method for manufacturing a printed wiring board according to a first embodiment of the present invention in the order of steps. (A) is a cross-sectional view showing a copper-clad laminate, (b) is a cross-sectional view showing a state where holes are drilled, (c) is a cross-sectional view showing a state where holes are filled with a conductive paste, and (d) is a conductor pattern. FIG. 4E is a cross-sectional view showing a state after the formation of the electroless solder plating, FIG. 4E is a cross-sectional view showing a state after the electroless solder plating, and FIG.

FIG. 2 is a sectional view illustrating a method for manufacturing a printed wiring board according to a second embodiment of the present invention in the order of steps. (A) is a cross-sectional view showing a copper-clad laminate, (b) is a cross-sectional view showing a state where holes are drilled, (c) is a cross-sectional view showing a state where holes are filled with a conductive paste, and (d) is a conductor pattern. FIG. 4E is a cross-sectional view showing a state after forming a solder resist, and FIG. 4E is a cross-sectional view showing a state after forming a solder resist. (F) is a sectional view showing a state after electroless solder plating, and (g) is a sectional view showing a state after fusing.

FIG. 3 is a cross-sectional view illustrating a method of manufacturing a printed wiring board described in JP-A-62-193197 in the order of steps. (A)
Is a cross-sectional view showing a copper-clad laminate, (b) is a cross-sectional view showing a state where holes are drilled, (c) is a cross-sectional view showing a state where holes are filled with a conductive paste, and (d) is plated with copper. FIG. 4E is a cross-sectional view showing a state, and FIG. 4E is a cross-sectional view showing a state after a conductor pattern is formed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Copper-clad laminate 2 Conductive paste 3 Copper plating 4 Solder layer 5 Solder resist

Claims (3)

(57) [Claims] 1. A step of: (a) drilling a hole in a desired location of a copper clad laminate; and (b) a step of embedding a conductive paste in a location of the drilled hole of the copper clad laminate. (c) then forming a conductor pattern by dissolving and removing unnecessary portions by etching the copper clad laminate, Mu optionally substituted in (d) of the conductive paste embedded bore surface of the conductor pattern A method for manufacturing a printed wiring board, comprising: a step of forming a solder layer by electrolytic plating; and (e) a step of fusing the solder layer. 2. A hole filled with a conductive paste for duplex drilled in the copper-clad laminate connection at substitutional electroless plating at least a conductive paste filled holes surfaces thereof a land portion A method for manufacturing a printed wiring board, comprising: forming a solder layer; and fusing the solder layer to connect the conductive paste and the land. 3. A process according to claim 2 printed wiring board, wherein the formation of the solder layer in said substituted electroless plating is selectively performed.