JPS59144194A - Terminal for soldering ceramic substrate - 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 [Field of Application of the Invention] The present invention relates to a terminal for soldering a ceramic substrate, which prevents the terminal from peeling off from the substrate due to the force applied when connecting lead wires.

[Prior art]

Figure 1 is a side sectional view showing lead wires soldered to terminals of a printed circuit or the like on a conventional ceramic substrate, where 1 is the board, 2 is a metal layer terminal, 3 is a solder layer, and 4 is a lead wire. It is. In such applications, flexible cables are generally used as lead wires. Flexible cables consist of copper foil bonded to plastic film strips and may be considered to have no resistance to bending stresses. Further, in this case, the metal layer terminal is coated with a solder layer in advance, and the flexible cable is welded by a so-called reflow method. The welding between the metal layer of the terminal and the solder layer and between the solder layer and the cable is relatively strong, and the adhesion between the metal layer terminal and the ceramic substrate is stronger than that of the combination of dissimilar materials such as metal and porcelain. Therefore, migration is not performed and it is relatively weak. Furthermore, the adhesive force strength distribution varies widely and is unstable.

Lead wires may be pulled during assembly. In that case, if the tensile force is parallel to the surface of the ceramic substrate, no problem will occur between the metal layer terminal and the surface of the ceramic substrate because the shear stress is widely dispersed over the adhesion surface between the two and is weak. However, when the lead wire is pulled upward as shown in FIG. 1, this tensile force is concentrated at the weakest point, part B, and breakage begins from there. In this case, the tensile force A becomes a so-called peel load, which causes the lead wire to bend easily, causing the metal layers of the terminal to be peeled off one after another from the surface of the ceramic substrate.

[Purpose of the invention]

An object of the present invention is to provide a terminal for soldering a ceramic substrate, which prevents the terminal from peeling off from the surface of the ceramic substrate even if some tensile force is applied to the lead wire.

[Summary of the invention]

In order to achieve the above object, in the present invention, a metal layer terminal that is well welded with solder is adhered on the surface of a ceramic substrate, the terminal layer is covered with a solder layer, and the surface of this solder layer is further coated with these metal layer terminals. It was decided to provide means for preventing welding by solder from approximately the center to nearly half of the surface of the metal layer. In other words, even if a force that pulls the lead wire perpendicular to the board surface is applied, it will not cause a beer load, and in this case, the solder N (and the metal layers above and below it welded together), which can be considered a relatively strong rigid body, This is done so that tensile stress acts on the entire terminal surface.

[Embodiments of the invention]

FIG. 2 is a side sectional view for explaining the principle of the present invention, and shows that the tensile force A does not act as a beer load, but is dispersed over the entire surface of the metal layer terminal (and solder layer) and acts as a tensile stress. become. If this happens, the force acting per unit area will be weak, so no peeling will occur.

FIG. 3 is a plan view of essential parts of an embodiment of the present invention, where 5 is the flexible cable and 6 is its copper foil. The metal layer terminal is provided over a length L/2, but the surface of the solder layer thereon is such that only a length 2 section can be connected to #l'tfJ and N'4 of the flexible cable. Take the length! Since the solder layer is covered with a cover film or solder resist in the area where there is a difference,
The copper foil and solder layer do not weld together. Further, as shown in FIG. 4, the flexible cable may be covered with a cover film 7. Note that L3 is the width of the copper foil.

According to the present invention, the peel failure mode between the board 1 and the terminal 2 is changed to the failure mode between the solder layer 3 and the lead wire 4.
Peel breakage occurs only due to the shape effect of the lead wire, and the influence due to instability of the adhesive force between the board and the terminal is removed, and a constant peel breakage strength distribution determined by the constant width L3 force ζ is obtained. Furthermore, since the shape of the lead portion of the flexible cable can be made constant and the positioning with respect to the electrode terminal portion can be easily performed, it is also possible to correlate the peel breakage strength distribution between the lead and the terminal with the design target strength. In addition, although the case where a flexible cable is used was described in the said Example, when using a single wire, the mff1 can be substituted for a cover film or a solder resist.

C. Effects of the Invention] As explained above, according to the present invention, peeling of the terminal from the ceramic substrate can be prevented by extremely simple means.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view showing a state in which a lead wire is soldered to a terminal for soldering of a conventional ceramic substrate, Fig. 2 is a side sectional view for explaining the principle of the present invention, and Fig. 3 is a side sectional view showing a state in which a lead wire is soldered to a terminal for soldering of a conventional ceramic substrate. FIG. 4 is a plan view of the main part of one embodiment, and FIG. 4 is a plan view showing near the end of the flexible cable of the embodiment. 1. Board, 2. Metal layer terminal, 3.-Solder layer, 4.- Lead wire, 5. Flexible cable, 6. Copper foil, 7. Cover film. Irg Tsuno // No. 20 ↑A

Claims (1)

[Claims] A metal layer terminal that welds well with solder is attached on the surface of the ceramic substrate, the terminal layer is covered with a solder layer, and further, on the surface of this solder layer, from approximately the center to nearly half of the surface of these metal layers, A terminal for soldering ceramic substrates characterized by having a means to prevent welding by solder.