JPS631094A - Flexible and rigid printed wiring hybrid board - 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] [Table of Contents] - Overview, industrial application field, conventional technology (Fig. 4) - Problems to be solved by the invention, means for solving the problems, actions, and implementation Examples (Figures 1, 2, 3) - Effects of the invention [Summary] A flexible and rigid printed wiring composite board,
A flexible substrate and a rigid substrate are bonded via an insulating adhesive layer, and the through holes of both substrates are connected to each other, or the through holes and the connection pattern are connected to each other. The two substrates are reliably connected by providing a slit groove through which molten solder can enter due to its surface tension, and the through holes of the two substrates are formed to have the same inner diameter.
It is possible to remove solder buildup on the through-hole lands exposed to the outside of both boards, and to make the insides of the through-holes of both boards hollow, and in particular, it is possible to improve the reliability of the connection part. This is what I did.

[Industrial application field]

The present invention relates to a flexible and rigid printed wiring composite board formed by bonding a flexible printed wiring board (flexible board) and a rigid printed wiring board (rigid board) via an insulating adhesive. The present invention relates to a connection structure between a through hole or a connection pattern of a rigid printed wiring board. Note that here, the term "flexible printed wiring board" refers to a flexible printed wiring board, and the term "rigid printed wiring board" refers to a rigid printed wiring board.

In recent years, there has been a strong demand for electronic devices to be lighter, thinner, shorter, and more compact, and to improve productivity.In response to these demands, we have developed rigid substrates that are excellent for component mounting, planar wiring, and planar circuit configurations, and flexible substrates that can be used for three-dimensional wiring configurations. A composite board has been developed that is formed by combining and bonding excellent flexible boards and has the function of a multilayer wiring board and the connection function of a flexible board.

One important point in the construction of this type of composite board is the quality of the electrical connection between the flexible board and the rigid board by soldering.

[Prior Art] FIG. 4 is a side sectional view showing the main parts of a conventional flexible and rigid printed wiring composite board. In the figure, numeral 1 is a flexible printed wiring board (hereinafter referred to as FPC board), 2 is a rigid printed wiring board (hereinafter referred to as RPC board), 3 is an adhesive layer made of insulating adhesive, and 4 is a solder layer. Each is shown below. In this conventional example, through holes 1-1 and 1-2 formed at predetermined positions on an FPC board 1 are RPC
The through holes 2-1 and connection patterns 2-2 formed in the substrate 2 are arranged in alignment with each other, and the FPC substrate 1 and the RPC substrate 2 are bonded via the adhesive layer 3. Holes 1-1 and 1-2 are RP
It is connected to the through hole 2-1 and the connection pattern 2-2 of the C substrate 2, respectively, thereby forming the connection part P.

In this case, the inner end surface 3a of the adhesive layer 3 at the connection part P is connected to the through holes 1-1, 1- of the FPC board 1.
It is formed to have approximately the same inner diameter as the inner circumferential surface of No. 2. Furthermore, code 1
a is the inner surface plating layer applied to the inner surfaces of the through holes 1-1 and 1-2 of the FPC board 1, and 1b is the inner surface plating layer 1.
2a is a through-hole land formed on the upper and lower surfaces of the board 1 by a continuous plating layer, and 2a is an inner plating layer applied to the inner surface of the through hole 2-1 of the RPC board 2;
b indicates a through-hole land formed on the upper and lower surfaces of the substrate 2 by a plating layer continuous with the inner surface plating layer 2a. Furthermore, in this conventional example, the diameter of the through hole of the FPC board 1 connected to the through hole 2-1 of the RPC board 2 is formed larger than the inner diameter of the through hole 2-1 of the RPC board 2, and both There is a step in between.

That is, since the adhesive layer 3 is not wetted by the solder (does not adhere), the solder forms a bridge shape to connect the through hole 1-1 of the FPC board 1 and the through hole 2-1 of the RPC board 2 as shown in the figure. Therefore, the above-mentioned step is required.

[Problem that the invention seeks to solve]

The above conventional example has the following problems.

■ The inner end surface 3a of the adhesive layer 3 at the connection part P is approximately the same as the inner peripheral surface of the through holes 1-1 and 12 of the FPC board 1.
Since the solder 4 is formed on the inner diameter, the solder 4 does not wet the inner end surface 3a of the adhesive layer 3 during soldering, but is instead repelled, so that the through hole 11 forms a bridge shape as described above. 1-2 and the through-hole 2-1 and connection pattern 2-2 of the RPC board Fi2 are connected, and the bonding area to the through-hole land 2b of the RPC board 2 or the connection pattern 2-2 becomes small, and the connection state is changed. There is a problem that the connection becomes unstable and the reliability of the connection is low. In particular, through holes 1-2 of FPC board 1 and RPC board 2
When connecting the connection pattern 2-2, the solder 4 is likely to be repelled by the adhesive layer 3, resulting in poor connection.

■ Through hole 1-1 of FPC board 1 and RPC board 2
When connecting the through hole 2-1, the inner diameter of the through hole 1-1 needs to be larger than the inner diameter of the through hole 2-1, so the connecting part P becomes large and the wiring of the FPC board 1 Efficiency is reduced.

Furthermore, for the reason stated in item 0 above, it is necessary to sufficiently fill both the through-holes 1-1 and 2-1 with the solder 4 and to solder in a manner that it is raised on the through-hole lands lb and 2b. The amount of 4 used increases,
Furthermore, since there is a bulge of solder 4, it is difficult to make the board multilayered.

■ As mentioned in ■ above, through hole 1-1゜2-1
Since the solder 4 is filled in the solder 4, there is an inconvenience that it is not possible to insert a component lead (not shown) and mount the component there.

The present invention was created in view of the above-mentioned problems, and makes it possible to reliably connect an FPC board and an RPC board, thereby increasing reliability and preventing an increase in the size of the connection part and a decrease in wiring efficiency. Flexible and rigid printing layouts, VL?, which can reduce the amount of solder used, make the board multilayered, and eliminate the inconvenience of mounting components. The purpose is to provide a one-piece board.

[Means for solving problems]

As a means for solving the above problems, in the present invention, as illustrated in FIGS. 1 and 2, a flexible printed wiring board (1) and a rigid printed wiring board (2) are bonded with an adhesive layer ( 3), and both the substrates (1,
2) A flexible and rigid printed wiring composite board formed by connecting the through holes to each other or connecting the through holes to the connection pattern, the flexible printed wiring board (1)
) of the adhesive layer (3) in the connection part (Q) for connecting the through hole (1-1) of the rigid printed wiring board (2) or the connection pattern. The inner end surface is connected to the through hole (1-1 or 2-1).
) is formed by regressing outward in the radial direction from the inner surface of the flexible substrate (1) and the rigid substrate (2) at the connection portion (Q), and allows molten solder to enter between the flexible substrate (1) and the rigid substrate (2) due to its surface tension. A flexible and rigid printed wiring composite board is provided, characterized in that a concave slit groove (5) is provided along the circumferential direction of the inner surface of the through hole (1-1, 2-1).

[Function] By providing a slit groove (5) in the connection part (Q) between the flexible board (1) and the rigid base plate (2), molten solder is prevented from flowing when soldering is performed by a method such as a solder dip. The solder enters the slit 1 (5) due to the action of surface tension, and even if the excess solder is removed by a solder leveler etc. after the solder dip, the solder remains in the slit 1 (5), and this solder causes the If & (1 , 2) through-hole land (
lb.

2b) They can be reliably connected. and,
By providing the slit groove (5), the inner diameter of the through hole (1-1) of the substrate (1) can be formed to be the same as the inner diameter of the through hole (2-1) of the substrate (2). 1, 2) through-hole lands (lb
, 2b) can be removed, and the insides of the through holes (1-1, 2-1) can be made hollow.

〔Example〕

FIG. 1 is a side sectional view showing a main part of an embodiment of the invention, FIG. 2 is an external perspective view of the embodiment of the invention, and FIG. 3 is a diagram showing an experimental example of the invention. In addition, in these figures, the above-mentioned fourth
The same or equivalent parts as those in the figure (conventional example) are denoted by the same reference numerals.

In Figures 1 and 2, reference numeral 1 is a flexible printed wiring board (hereinafter referred to as FPC board), 1-1 is a through hole provided in the board 1, and la and 1b are through holes (1-1).
-1) inner surface plating layer and through hole land, 2 is rigid printed wiring board (hereinafter referred to as RPC board), 2-
1 is a through hole provided in the substrate 2, 2a and 2b are the inner surface plating layer and through hole land of the through hole (2-1), and 3 is interposed between the substrates 1 and 2, and both of these (1, 2) are provided. 3a is the inner end surface of the adhesive layer (3), 4 is solder, and Q is the connection formed according to the present invention. 5 is the connection part Q. Each of the formed slit grooves having a concave cross section is shown.

The external appearance of this example is as shown in FIG.
The entire surface of the FPC board 2 is bonded via an adhesive layer 3, a connection part Q is provided at a predetermined position, a part of the edge of the FPC board 1 is extended and bent, and three-dimensional wiring is possible. As a result, a composite board is formed that has the function of a multilayer wiring board and the function of connecting with other FPC boards.

The main feature of this example is that, as shown in FIG. ) The inner end surface 3a of the adhesive layer 3 at Q is sufficiently retracted from the inner peripheral surface of the through hole 1-1 (2-1) in the radial direction of the through hole 1-1,
Through holes 1-1 (2- 1) is provided along the circumferential direction. The depth Ds of the slit groove 5 is set sufficiently large relative to the width ts (strictly speaking, the mutual distance between the through-hole lands 1b and 2b), and the slit groove 5 is formed so that the molten solder 4 can enter by the action of its surface tension. Ru. FIG. 3 is a diagram showing the setting ranges of the width ts and depth Ds of the slit groove 5 determined through experiments. As shown in FIG. 3, the area is divided into a good connection area (an area where molten solder can enter the slit groove) and a poor connection area with the connection failure limit line as a boundary. Therefore, for example, the width ts of the slit groove 5 is 40 μm.
m, the depth Ds should be approximately 0.35fl (350μ
(Fig. 1)
is obtained. Note that the connection pattern between the through hole 1-1 of the FPC board 1 and the RPC board 2 (not shown, 2-1 in Fig. 4)
2), a good connection can be obtained by providing the slit groove 5 in the same manner as described above.

In this example, by providing the slit l-a5 as described above, the molten solder enters into the slit groove 5 due to its surface tension when soldering is performed by a method such as a solder dip. Even if the excess solder is removed by blowing hot air onto the connection part Q using a solder leveler or the like, as shown in FIG.
1, on the inner surface of 2-1 and on the top surface of FPC board 1 and RPC
Through-hole land lb exposed on the bottom surface of the board 2,
The solder that remains as a thin solder layer on 2b and enters into the groove 5 is not removed and is removed from the through-hole land lb.
, 2b can be reliably connected to each other.

Therefore, according to this example, the connection between the FPC board 1 and the RPC board 2 can be reliably made, and the inner diameter of the through hole 1-1 of the FPC board 1 can be set to the inner diameter of the through hole 2-1 of the RPC board 2. It is possible to remove the swelling of the solder 4 on the vertically exposed through-hole lands lb, 2b, and to make the inside of the through-hole Ll, 2-1 hollow.

It should be noted that the present invention is of course applicable to the case where the through holes 1-1 and 2-1 do not have the same inner diameter (different diameters) as in the above embodiment. However, in this case, the wiring efficiency decreases.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, a slit groove is formed in the connecting portion (Q) of the flexible printed circuit board (FPC board) (1) and the rigid printed circuit board (RPC board) (2). By creating a structure with (5), the FP
It is possible to reliably prevent the occurrence of connection failures between the C board (1) and the RPC board (2), and to greatly increase the multiplicity of connections. In addition, the through hole (1-1) of the FPC board (1)
) through hole (2-1) of RPC board (2)
Since the inner diameter of the FPCJJ board 1 can be the same as that of the FPCJJ board 1, the wiring efficiency of the FPCJJ board 1 can be improved. Also, half 1) on the through-hole land (lb, 2b) exposed to the outside
4) can be removed and the through hole (1-1
, 2-1) can be made hollow, making it possible to further multilayer the board and reduce the amount of solder (4) used, as well as solving the inconvenience of mounting components. .

[Brief explanation of the drawing]

Fig. 1 is a side sectional view showing the main parts of the embodiment of the present invention, Fig. 2 is an external perspective view of the embodiment of the invention, Fig. 3 is a diagram showing an experimental example of the invention, and Fig. 4 is a diagram of the conventional example. FIG. 3 is a side sectional view showing main parts. In Figure 1.2.3, 1 is a flexible printed wiring board (flexible printed wiring board:
FPC board), 2 is a rigid printed wiring board (rigid printed wiring board: RPC
(substrate), 1-1.2-1 is a through hole, la, 2a is an inner plating layer, lb, 2b is a through hole land, 3 is an adhesive layer made of insulating adhesive, 3a is an inner end surface, 4 is solder, 5 is the slit groove, Q is the connection part (solder connection part), ts is the slit groove width, and Ds is the slit groove depth.

Claims (1)

[Claims] 1. A flexible printed wiring board (1) and a rigid printed wiring board (2) are bonded via an adhesive layer (3) made of an insulating adhesive, and A flexible and rigid printed wiring composite board formed by connecting through holes to each other or connecting through holes to a connection pattern, wherein the through holes of the flexible printed wiring board (1) (
1-1) and the through hole (2-1) or connection pattern of the rigid printed wiring board (2). (1-1 or 2-1) is formed by regressing outward in the radial direction from the inner surface of the flexible substrate (1-1 or 2-1), and the molten solder is formed between the flexible substrate (1) and the rigid substrate (2) at the connection portion (Q). The slit groove (5), which has a concave cross section and can be entered by its surface tension,
2-1) A flexible and rigid printed wiring composite board characterized by being provided along the circumferential direction of the inner surface.