JPH0383394A - Manufacture of printed circuit board - Google Patents

Abstract

PURPOSE:To interconnect conductor patterns of both side surface of a base material without forming a copper plating film on the inner wall surface of a through hole by electrically connecting the conductor patterns of both side surfaces of the base material to each other by metal rods. CONSTITUTION:After a through hole 3 is formed in a base material 1, a rod 4 made of a conductive material (e.g. brass, etc.) is engaged within the hole 3. After cream solder 6 is melted by an infrared ray, hot blast, etc., in a state that the lead 10a of a component (resistor) 10 is brought into close contact with the solder 6, it is cured to electrically interconnect conductor patterns 2 of both side surfaces of the material 1 to each other by the metal rod 4 and to connect the leads 10 of the component to the patterns 2. According to this method, a surface mounting both-side type printed circuit board can be manufactured without necessity of a plating step.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for manufacturing a printed wiring board, and more particularly to a method for manufacturing a double-sided printed wiring board for surface mounting.

<Prior Art> As a method for mounting electronic components and the like on a printed wiring board, for example, as shown in FIG. There is a so-called flow soldering mounting method in which the lead 40a is inserted and the lead is soldered to the copper plating film 44 in the through hole portion by flow soldering. In this mounting method, conventionally, an IP (dual in line) type IC as shown in FIG. 6(a) is used.
, LSI, and components such as resistors with insertion leads as shown in the same figure) are mounted.

Incidentally, recently, ICs and LSIs have been rapidly becoming denser and larger, and the number of gates has increased significantly. For this reason, it has become impossible to accommodate input/output terminals in conventional DIP types. Therefore, in response to the increasing density of ICs and LSIs, flat package types with leads on all sides as shown in Figure 7(a) and leadless ceramic carriers as shown in Figure 7(a) are available. electronic components with smaller leads and narrower lead pitches have come to be manufactured. Also,
The resistor is also manufactured in a shape as shown in the same figure (C).

To mount such a component on a printed wiring board, for example, as shown in FIG. So-called surface mounting is performed in which the leads loa are connected to the copper plating 34 by reflowing (remelting) the solder 6 while the leads 10a are in contact with each other. Furthermore, by using this type of surface mounting, there is no need to insert component leads into through-holes, and the diameter of through-holes can be made as small as possible, making it possible to increase the density of the printed wiring board itself. becomes.

Now, FIG. 3 shows a manufacturing procedure for a printed wiring board used in surface mounting and a procedure for mounting components on the wiring board.

First, as the basic material of the printed wiring board, as shown in (a), a base material 31 with copper foil 32 uniformly formed on both sides is used. In addition, as the material of the base material 31, -S
For this purpose, polyimide, polyester, phenol, epoxy, composite, glass epoxy, glass imide, etc. are used, and the thickness thereof is usually 0.1 to 1.6 m.
It is about m. Further, the thickness of the copper foil 32 is 18 μm or 35 μm, and the former is used for fine pattern formation.

Next, the base material 31 and the copper foil 32 are drilled, etc.
Open the hole 33 with a diameter of about 0.4 to 0.7 b), then 20 μm on the surface of the copper foil 32 and the inner wall of the hole 33.
After forming the copper plating film 34-like to the extent (C), the base material 3
One side is covered with a negative dry film 37 (
d).

Next, a photo tool 38 such as a glass dry plate or film is placed on the dry film 37.e) In this state, the portions of the copper coating film 34 and the copper foil 32 to be left are exposed to ultraviolet light, and then, Development is performed using a calcium hydroxide solution. At this time, the part irradiated with ultraviolet light is hardened and not dissolved by the calcium hydroxide solution, but the other part is dissolved, and as shown in (f), the copper coating film 3
4 is exposed.

Next, etching is performed using cupric chloride or ferric chloride solution to remove the exposed copper plating film 34 and the underlying copper foil 32, and then the dry film 37 on the copper plating film 34 is hydrated. After peeling off with a sodium solution (g), the exposed surface of the base material 3 is covered with a solder resist 35 to form a base material 3 as shown in (h).
A double-sided printed wiring board is obtained in which a conductor pattern 32 is formed on both sides of the substrate 1 and the conductor patterns 32 on both sides are connected to each other by a hole 33 in a base material, that is, a copper plating film 34 in a through-hole portion.

The mounting of components on such a printed wiring board is
First, adhesive 9 for temporarily fixing the component and cream solder 6 are sequentially applied on the copper plating film 34 of the part where the leads of the component are connected (i), and the component (resistor) 10 is applied to the cream solder 6. With the lead 10a of (j
), the component glue 10a is soldered to the copper plating film 34 by melting and hardening the cream solder 6 using infrared rays, hot air, etc. (k).

<Problems to be Solved by the Invention> However, according to the method for manufacturing a double-sided printed wiring board described above, the following problems remain.

(1) Etching process (side etching occurs on the copper foil in the chain. This is because as the etching progresses, the side part of the copper foil is exposed to the etching solution and a part of it is scraped off. The amount of etching increases as the thickness of the copper foil increases.In other words, as shown in the schematic diagram in Fig. 8, when copper of different thicknesses d, , d are etched under the same conditions, thin copper (a)
The side etch amount is α1 ”” d 1/ja
On the other hand, for thick copper (b), (X z =
d z /tan θ, and therefore, as the thickness of copper increases, the amount of side edges increases in proportion to the thickness. Therefore, in order to reduce the effects of such side etching, a thin copper foil of 18 μm is conventionally used, but during etching,! 20 μm on l1iI foil
Since a copper plating film of approximately 38 μm is formed, in order to pattern the copper foil into the desired shape, it is essentially necessary to perform etching of approximately 38 μm, resulting in a large amount of side etching of the copper foil. . In this way, if the amount of side etching of the copper foil is large, it not only becomes a hindrance to increasing the density of printed wiring boards in response to the increasing density of mounted components, but also deteriorates the accuracy of pattern etching. cause to bring about.

(2) Copper plating and plating films on the inner wall surface of the through-hole and the copper foil are usually formed by electroplating with the base material immersed in a plating bath, so the pore diameter of the through-hole is large. In this case, as shown in FIG. 9(a),
Copper adheres sufficiently to the inner wall surface of the through-hole 33, but when the diameter of the through-hole is made small in order to increase the density, the plating liquid does not enter the through-hole sufficiently. As shown in (b), there is a portion on the inner wall surface of the through hole 33 where copper does not adhere, and there is a possibility that the through hole will be damaged. In addition, in the subsequent etching process, the etching solution may enter the boundary between the copper plating film and the dry film, etching the copper plating film on the inner wall of the through hole, resulting in through hole defects. There is also a possibility that

(3) The plating process takes a lot of time and is expensive.

Here, the interconnection of the conductor patterns on both sides of the base material is performed using the copper plating film formed in the through hole part.
This is because leads need to be inserted into through-holes in components such as quibs.In surface mounting, through-holes simply need to be used to interconnect conductor patterns on both sides of the board; There is no need to use a plating film.

An object of the present invention is to manufacture a double-sided printed wiring board for surface mounting without requiring a plating process.
The purpose is to provide a method.

<Means for Solving the Problems> As shown in FIG. 1 corresponding to an embodiment, the present invention provides that after forming a through hole 3 in a base material 1 (b), a conductive material ( For example, a rod 4 made of brass or the like is fitted (i).

As shown in FIG. 1), it is characterized by electrically connecting the conductive patterns 2 on both sides of the base material 1 with solder 5, for example, using the strips 4.

<Function> It becomes possible to connect the conductor patterns 2 on both sides of the base material 1 to each other without forming a copper plating film on the inner wall surface of the through hole 3 formed in the base material 1, and the plating process can be omitted. .

<Example> FIG. 1 is a diagram illustrating the procedure of the manufacturing method of the present invention and the procedure of mounting components.

First, as shown in (a), as the basic material of a printed wiring board, a base material 1 with copper foils 2 of 18 μm thick uniformly formed on both surfaces is used, as in the conventional case. This base material 1 and copper foil 2 are drilled, etc. to form a diameter of 0.4 to 0.7 mm.
After drilling holes 3 of approximately 100 mL (b), both sides of the base material 1 are covered with a negative dry film 7 (c).

Next, accurately position the photo tool 8 such as a glass dry plate on the dry film 7 (d), and in this state, place the copper foil 2
The portion to be left is exposed to ultraviolet light, and then developed with a calcium hydroxide solution.

At this time, the dry film 7 in the area irradiated with ultraviolet light
is hardened and not dissolved by the calcium hydroxide solution, but other parts are dissolved and the copper foil 2 is exposed as shown in (e).

Next, etching is performed using a cupric chloride or ferric chloride solution to remove the exposed portion of the copper foil 2 and paqueuning the copper foil 2. Next, the dry film 7 on the copper foil 2 is etched with water. After exfoliation with sodium oxide solution (f),
The exposed surface of the base material 1 is covered with solder resist 5 (cloudy).

Next, a fixing adhesive 9 and cream solder 6 are sequentially applied to the copper foil or conductor pattern 2 around the hole 3 (5), and then a metal rod 4 such as brass is inserted into the hole 3 (5).
i) Apply cream solder 6 to the exposed part of the metal rod 4, and then apply cream solder 6 using infrared rays, hot air, etc. while keeping the lead 110a of the component (resistor) 10 in close contact with the cream solder 6 (j). By melting and curing the solder 6, as shown in (2), the conductor patterns 2 on both sides of the base material 1 are electrically connected to each other by the metal rod 4, and the component glue 10a is connected to the conductor pattern. Connect to 2.

According to the above procedure, since there is no etching step after the metal rod 4 is attached, there is no risk of corrosion of the metal rod 4, and the conductor patterns 2 on both sides of the base material 1 can be reliably connected. Moreover, the components 10 can be mounted simultaneously with the interconnection of the conductive patterns 2 by the metal rods 4, and the process can be simplified.

FIG. 2 is a diagram illustrating the procedure of another manufacturing method of the present invention and the component mounting procedure.

First, as in the previous example, a base material 1 with copper foil 2 formed on both sides of the base material 1 as shown in (a) is used as the basic material of the printed wiring board. Hole 3 is drilled in (b).

Next, after inserting the brass-shaped metal rod 4 into 7L3 (C),
Solder both ends of the metal rod 4 to the copper foil 2 (d)
. At this time, both ends of the metal rod 4 exposed to the outside are completely covered with the solder 26.

Next, after covering both sides of the base material 1 with a negative dry film 27 (e), the photo tool 28 is accurately positioned on the dry film 27 (f), and in this state, the copper foil 2 is left behind. The unnecessary portions of the copper foil 2 are exposed by exposing the desired portions to ultraviolet light and then developing in a calcium hydroxide solution (chains).

Next, etching is performed using cupric chloride or ferric chloride solution to remove the exposed portion of the copper foil 2 and patterning the copper foil 2. Next, the dry film 27 on the copper foil 2 is etched with water. Q'1 after peeling with sodium oxide solution
), by covering the exposed surface of the base material 1 with a solder resist 5, a double-sided printed wiring board in which the conductor patterns 2 on both sides of the base material 1 are connected to each other by metal rods 4 as shown in (i) is fabricated. obtain. To mount the components on the wiring board, adhesive 9 for temporarily fixing the components and cream solder 6 are sequentially applied on the conductor pattern 2 at the part where the leads of the component are connected, and then the cream solder 6 is With the leads 10a of the component 10 in close contact with each other (j), the cream solder 6 is melted using infrared rays or the like, and then hardened to connect the component F 10 a to the conductor pattern 2.
(k).

According to the above procedure, after the metal rod 4 is soldered to the copper foil 2, the copper foil 2 is etched, and during etching, both ends of the metal rod 4 are completely etched with the etching-resistant solder 26. Since the metal rod 4 is coated with the metal rod 4, there is no fear that the metal rod 4 will corrode, and the conductor patterns 2 on both sides of the base material 1 can be reliably connected by the metal rod 4.

<Effects of the Invention> As explained above, according to the present invention, since the conductor patterns on both sides of the base material are electrically connected by a metal rod, the plating process that was conventionally performed can be omitted, and the manufacturing time can be shortened. ,
-In turn, it is possible to reduce product costs.

In addition, since the metal rod is not exposed during machining and etching during a series of processes, there is no risk of through-hole damage caused by the etching solution, and even if the through-hole diameter is made small, the Since the conductor patterns on both sides of the material can be reliably connected using metal rods, there is no risk of through-hole defects even when increasing the density of printed wiring boards in response to the increasing density of mounted components. do not have.

Furthermore, when patterning the copper foil on the base material, it becomes possible to directly etch the copper foil, and as a result, the influence of side etching can be reduced compared to the conventional method, resulting in improved patterning accuracy.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating the steps of the manufacturing method of the present invention and the steps of mounting components. FIG. 2 is a diagram illustrating the procedure of another manufacturing method of the present invention and the component mounting procedure. FIG. 3 is a diagram illustrating a conventional manufacturing procedure for a double-sided printed wiring board for surface mounting and a procedure for mounting components on the wiring board. FIG. 4 is a sectional view showing a structure in which components are mounted on a printed wiring board using a flow soldering mounting method, and FIG. 5 is a longitudinal sectional view showing a structure in which components are mounted on a printed wiring board using a surface mounting method. FIG. 6 is an external view of parts for flow soldering mounting, and FIG. 7 is an external view of parts for surface mounting. 8 and 9 are diagrams for explaining problems in the manufacturing procedure shown in FIG. 3. FIG. 1... Base material 2... Copper foil 3... Hole 4... Metal rod 5... Solder resist 6... Cream solder 10... Mounted component (resistor) 10a... Lead

Claims (1)

[Claims] In a method for manufacturing a double-sided printed wiring board, a through hole is formed in a base material, and then a rod made of a conductive material is fitted into the through hole, and the rod is used to electrically connect the conductive patterns on both sides of the base material. 1. A method for manufacturing a printed wiring board, characterized in that the printed wiring board is connected to.