JPS6330793B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for connecting the front and back sides of a flexible double-sided wiring board to which a hard board is attached, which is used in electronic equipment.

Structure of conventional example and its problems In the conventional double-sided printed wiring board, as shown in FIG. Either plating 5 around the inner surface of the hole 4, inserting a through hole pin 6 shown in FIG. 2b into the through hole 4 as shown in FIG. 2a, and fixing it with solder 7, or
Alternatively, as shown in FIG. 3a, the through-hole eyelet 8 shown in FIG. 3b is inserted into the through hole 4, caulked, and then fixed with solder 7 to connect the front and back sides.

In a double-sided printed wiring board with front and back connections connected as described above, the insulating substrate 1 expands and contracts due to changes over time due to the influence of heat or temperature, and the expansion and contraction of the insulating substrate 1 in the thickness direction is particularly large. Since the expansion coefficients of the solder 7, through-hole eyelets 8, etc. are smaller than the expansion coefficient of the insulating substrate 1, cracks are likely to occur in the soldered parts of the upper conductive foil layer 2 and the lower conductive foil layer 3, resulting in disconnection of front and back conduction. The drawback is that it often happens.

In addition, as shown in FIG. 4, a double-sided printed wiring board that solves the above-mentioned drawbacks is provided with first and second through holes 4a and 4b in the double-sided printed wiring board, and a through-hole eyelet 8 in the first through hole 4a. There is a method in which the jumper wire 9 is inserted and caulked, and then both ends of the jumper wire 9 are inserted into the first and second through holes 4a and 4b and soldered from the bottom surface of the double-sided printed wiring board. The through-hole eyelet 8 used in this double-sided printed wiring board has the function of guiding the solder from the bottom surface to the top surface of the printed wiring board by flow hand jet pressure during soldering, and also has the function of guiding the solder from the bottom surface to the top surface of the printed wiring board. , 3.

In this double-sided printed wiring board, the upper and lower conductive foil layers 2 and 3 are electrically connected by through-hole eyelets 8 and jumper wires 9, and in particular, the jumper wires 9, the upper conductive foil layer 2, and the lower conductive foil The connection positions of layer 3 are different on the top and bottom surfaces of this printed wiring board, and the jumper wire has elasticity, so even if this double-sided printed wiring board expands and contracts and stress is applied in the board thickness direction, the connection parts will not be damaged. There is no damage, and the reliability of the connection between the front and back sides is high.

However, as the trend toward smaller and lighter electronic devices is increasing, and there is a need to increase packaging density, it is necessary to connect the front and back sides as in the conventional example above.
Providing the first and second through holes has the disadvantage that the board space cannot be used effectively.

Purpose of the Invention In order to solve the above-mentioned drawbacks, the present invention is capable of high-density packaging, has high reliability of front and back electrical connections, and
Moreover, it is an object of the present invention to provide an economical method for connecting the front and back sides of a flexible double-sided wiring board.

Structure of the Invention In order to achieve the above object, the present invention comprises a single-sided flexible printed wiring board and a single-sided copper-clad printed wiring board,
Paste them together with an elastic adhesive with the conductive circuit on the outside, apply cream solder to the conductive land around one side of the through hole through the through hole for connecting the front and back sides, and then insert a pin or eyelet into the through hole. It is inserted and fixed with cream solder, and then the conductive land around the other side of the through hole is soldered with molten solder to fix the pin or eyelet.

Since an elastic adhesive is used between the flexible printed wiring board and the single-sided copper-clad printed wiring board, the conductive lands on the front and back sides are fixed by pins or eyelets, and the board thickness may change due to stress due to heat or temperature or changes over time. Even when stress is applied in the direction, the adhesive exhibits a cushioning effect, the electrical connection portion is not damaged, and the reliability of the front-back connection is high.
Furthermore, since the front and back connections are made through one through hole, the space of the printed wiring board can be used effectively. Furthermore, unlike through-hole plating, a flexible double-sided wiring board with front and back connections can be manufactured at low cost without requiring many manufacturing processes, material consumption, pollution control, etc.

DESCRIPTION OF EMBODIMENTS A method for connecting the front and back sides of a flexible double-sided wiring board according to an embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 5, an insulating base material 11 having a copper foil 10 on one side, a so-called single-sided copper clad laminate 12, an acrylic elastic adhesive film 13,
For example, double-sided adhesive tape (No. 500 manufactured by Nitto Denko, No. 464 manufactured by Sumitomo Three M) is applied. A protective film may be provided on the adhesive film 13 to improve workability. Next, the required shape is punched, and then the protective film is removed, and the copper foil 1
4 is attached to the adhesive film 13. Here, the copper foil pattern may be formed in advance by well-known screen printing or etching methods, or may be formed after being applied to an adhesive. Next, solder resists 16 and 17 are formed by a screen method, leaving the soldered portions. Here, the solder resist 16 may be a flexible coverlay. Next, a flexible double-sided wiring board is obtained by providing through holes 18 at predetermined positions.

Cream solder 20 is formed by screen printing on the copper foil land 19 around the through hole 18 on the flexible film 15 side of the flexible double-sided wiring board produced by the above method. Next, as shown in FIGS. 6 and 7, the other cream solder 19 has a plurality of notches 21 having a cylindrical shape and exhibiting elasticity with respect to the cylindrical axis.
It has a plurality of notches 22 in the part to which it is fixed,
At the time of insertion, an eyelet 24 is caulked to the chrysanthemum-shaped radial portion 23 on the surface of the copper foil land 19. Here, the notch 21 can be physically fixed to the through hole 18 by utilizing its elasticity when the eyelet 24 is inserted. Moreover, the chrysanthemum-shaped radial portion 23 is used to increase the contact area with the cream solder and to strengthen the soldered connection.

Next, the double-sided wiring board is heated to 180 to 250°C to melt the cream solder 20 and connect and fix the eyelet 24 and the copper foil land portion 19. Next, the single-sided printed wiring board side is soldered using a flow solder, and the eyelet 24 and the copper foil land portion 25 are fixed with the solder 26, thereby making it possible to connect the front and back sides. Here, the cream solder 20 may be fixed by melting and fixing after soldering.

As described above, the front and back sides of the flexible double-sided wiring board are connected, and the one having the above-mentioned eyelet 24 structure is fixed to the through hole 18 and adhered or fixed with the cream solder 20 during the solder dip with the final flow solder. The eyelet 24 does not come up from the through hole, making it possible to perform soldering work with good workability.

As shown in FIG. 8, the copper foil land portion 27 and the copper foil land portion for connecting the chip component 28 around the through hole 18 on the flexible film 15 side of the flexible double-sided wiring board prepared in the above example are shown in FIG. Cream solder 3 on 29a and 29b
0 by screen printing, then insert the pin or eyelet 31 into the through hole 18, and attach the copper foil land part 2.
It is bonded to the terminal portions 33a, 33b of the chip component 28 via cream solder 30 so as to span 9a, 29b. Insertion of pins or eyelets and attachment of chip parts can be performed simultaneously by automatic insertion.

Next, the cream solder 30 is melted and fixed by heating to 180 to 250°C.

Next, copper foil land portions 34a and 34b corresponding to mounting the chip component 32 on the single-sided copper-clad wiring board side are installed.
After applying the adhesive 35 between them by screen printing or dispenser injection, solder dip is performed using a flow solder, and the pin or eyelet 31 is
connection with copper foil land 37 and chip component 32
terminals 38a, 38b and copper foil land portions 34a, 3
4b using solder 36, it is possible to connect the front and back sides of the flexible double-sided wiring board and to connect the chip components by soldering at the same time.

In explaining the embodiments of the present invention, it has been described that cream solder is applied to the copper foil land on the flexible film side and connected to pins or eyelets. Needless to say, it is also possible to apply cream solder to the land portion and connect it with a pin or eyelet.

Effects of the Invention As is clear from the above explanation, the present invention provides a flexible double-sided wiring board made by combining a hard board and a flexible board, which has high electrical connection reliability on the front and back sides, and can be mounted at high density at low cost. It has great utility value.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a conventional double-sided printed wiring board.
Figures 2a and 2b are a cross-sectional view of a conventional double-sided printed wiring board and a perspective view of a through-hole pin, respectively;
FIGS. 3a and 3b are a cross-sectional view and a perspective view of a through-hole eyelet of a conventional double-sided printed wiring board, respectively, FIG. 4 is a cross-sectional view of a conventional double-sided printed wiring board, and FIGS. A cross-sectional view of a wiring board formed by the method for connecting the front and back sides of a flexible double-sided wiring board in an example, FIG. 6 is a perspective view of an eyelet inserted into the wiring board, and FIG. 7 shows a state in which the eyelet is crimped. FIG. 10, 14...Copper foil, 11...Insulating substrate, 12
... Single-sided copper-clad laminate, 13 ... Adhesive film,
15... Flexible film, 18... Through hole, 19, 25, 27, 34a, 34b... Copper foil land portion, 20, 30... Cream solder, 21,
22...Notch, 23...Chrysanthemum-shaped radial part, 2
4, 31...eyelet, 26...solder.

Claims (1)

[Scope of Claims] 1. A single-sided flexible printed wiring board and a single-sided copper-clad printed wiring board are bonded to each other with a resilient adhesive with the conductive circuits on the outside, and the single-sided flexible printed wiring board and the single-sided copper-clad printed wiring board are bonded to each other with an elastic adhesive. A through hole for connecting the front and back sides that penetrates the printed wiring board is provided, cream solder is applied to the conductive land around one opening of the through hole, and the cream solder is used to attach the pin or eyelet to be inserted into the through hole. A method for connecting the front and back sides of a flexible double-sided wiring board, in which the conductive land portion around the other opening of the through hole and the pin or eyelet are soldered. 2. The pin or eyelet has a cylindrical shape, has a notch that shows elasticity with respect to the cylinder axis in the part inserted into the through hole, and has a plurality of notches in the part to be fixed with cream solder, A method for connecting the front and back sides of a flexible double-sided wiring board according to claim 1, wherein the flexible double-sided wiring board is caulked radially in a state inserted into a hole.