JPS6345015Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a structure for connecting circuits on both sides of a printed circuit board.

Conventionally, the method of connecting circuits on both sides of a printed circuit board was as follows:
As shown in FIG. 1, after forming holes through the substrate 1 for the conductors 2 and 3 on each side to be connected, a conductive film 4 is formed by plating method, and then the conductors 2 and 3 are connected. The so-called through-hole method, in which a predetermined circuit pattern is formed by chemical etching or the like, has generally been used. The lead wires 6 of the components 5 to be mounted on this board are inserted into the through holes and then soldered, and the through holes are filled with solder. However, when forming the conductive film 4, this method of connecting circuits on both sides of the substrate depends on the surface condition of the base material 1, which depends on the hygroscopicity and mechanical properties of the base material 1.
There is a risk that pinholes or cracks may occur in the conductive film 4, or the adhesion between the conductive film 4 and the base material 1 may be poor, causing the conductive film 4 to fall out through the through holes, which may significantly reduce the reliability of the circuit connection. It was hot.

The purpose of the present invention is to eliminate such drawbacks by connecting circuits on both sides of the board using metal tubes, and to provide a connection structure for printed circuit boards that has high mechanical strength and is inexpensive.

This invention provides through holes for connecting circuits on both sides of the board, and the through holes are filled with Ni-Ti alloy, Cu-
It is configured to attach a metal tube made of shape memory alloy such as Ni-Al alloy, and when the lead wire of the component is inserted into the metal tube and soldered, the specific shape is memorized at the soldering temperature. The metal tube is characterized by changing its shape so as to mechanically sandwich the circuit patterns on both sides, thereby firmly connecting the circuit patterns on both sides.

Next, the present invention will be explained with reference to the drawings.

The through hole for connecting the circuits on both the front and back surfaces 2 and 3 of the substrate 1 has a flange 8 at only one end below the transition point, but at a soldering temperature higher than the transition point, the flange 8' is made to protrude from the other end as well. A metal tube made of an alloy that has a shape memory property that forms an eyelet shape and then retains the eyelet shape even if the temperature drops below the soldering temperature is inserted into the through hole, and a lead wire for connecting an electronic component is inserted into the metal tube. This is a printed circuit board in which the circuits on both sides of the board are mechanically sandwiched and connected by soldering.

FIG. 2 shows one configuration diagram of the present invention, in which conductive patterns 2 and 3 are formed on both sides of a printed circuit board 1, and a metal tube 4' made of a shape memory alloy is attached to the through hole. A state in which the lead wire 6 of the component 5 is fixed by the solder 7 is shown.

The shape memory alloy used in this invention is
After molding at a temperature above TTR (Transition Temperature Range), cooling to below TTR, applying strain such as bending to the alloy, and heating it again to a temperature above TTR, it will return to the shape it had when molded above TTR. In general, alloys with the properties of
Ni-Ti alloys, Cu-Ni-Al alloys, etc. are known. FIG. 3 shows a sectional view of a metal tube 4' used in the present invention. Figure 3a shows a shape memory alloy molded at a temperature considerably higher than TTR, having a predetermined composition, and has a so-called eyelet shape. This metal tube was cooled to below TTR and the bent portion on one side (lower side in the figure) was processed into a straight line, as shown in Figure 3b.

The metal tube processed as shown in FIG. 3b is inserted into the through hole of the substrate 1 as shown in FIG. At this time, the conductive patterns 2 and 3 have already been patterned by chemical etching or the like. Insert the lead wire 6 of the component 5 into this metal tube 4', heat it by soldering or soldering dip, etc., and when the temperature reaches TTR or higher, the metal tube 4' will return to the shape shown in FIG. As shown in FIG. 2, the metal tube 4' mechanically firmly holds the conductive patterns 2 and 3, so that circuits on both sides can be connected. Note that it is desirable that the metal tube 4' be subjected to a surface treatment such as solder plating or gold plating in consideration of solderability.

As described above, according to the present invention, the soldering work and the crimping work can be performed at the same time, thereby saving man-hours, and since the circuit connection is made with a pattern on both the front and back sides using metal tubes, the mechanical strength is high. Therefore, a low-cost and highly reliable printed circuit board can be obtained.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view showing the connection structure of circuit patterns on both sides of a conventional printed circuit board, Figure 2 is a cross-sectional view of the structure of an embodiment of the present invention, and Figure 3 is the connecting parts used in the present invention. FIG. 4 is an explanatory diagram showing the connection process of the invention. In the figure, 1: substrate, 2, 3: conductor, 4,
4': Metal tube, 5: Electrical parts, 6: Electrical parts lead wire, 7: Solder.

Claims (1)

[Scope of utility model registration request] A through-hole for connecting circuits on both the front and back sides of the board has a flange at only one end below the transition point, but at a soldering temperature higher than the transition point, the flange protrudes from the other end as well, forming an eyelet-like shape, which then becomes difficult to solder. Inserting into the through hole a metal tube made of an alloy having shape memory properties that maintains the eyelet state even when the temperature drops below the temperature,
A printed circuit board in which lead wires for connecting electronic components are inserted into the metal tubes and soldered to connect the circuits on both sides of the board by mechanically sandwiching them.