GB2041808A

GB2041808A - Soldering Tool for Hybrid Circuits

Info

Publication number: GB2041808A
Application number: GB7904504A
Authority: GB
Original assignee: Standard Telephone and Cables PLC
Current assignee: STC PLC
Priority date: 1979-02-08
Filing date: 1979-02-08
Publication date: 1980-09-17
Also published as: GB2041808B

Abstract

A tool designed to effect simultaneous soldering or desoldering of all the contacts disposed around the four edges of an edge connected substrate carrying a hybrid circuit. The tool comprises a pair of rectangular low impedance electrically conducting pates 20, 21 spaced apart by a sheet 22 of insulating material, two pairs of and high impedance electrical heating elements 27 arranged on one side of the pair of plates, the heating elements being disposed all at the same distance from the nearest plate and defining an area beneath said plate corresponding to the shape of the plate, each adjacent pair of heating elements being electrically connected at their adjacent ends to the corner of one plate and at their other ends to the opposing corners of the other plate, and means for electrically connecting the two plates to the two poles of a source of electric current. <IMAGE>

Description

SPECIFICATION Soldering Tool for Mounting Hybrid Circuits This invention relates to a soldering tool for mounting (and demounting) hybrid circuits, as hereinafter defined, which are to be mounted in a supporting frame by means of soldered joints at the input and output connections to the circuits.

A 'hybird circuit" is defined as a circuit composed of one or a number of monolithic circuits used in combination with discrete electrical or electronic components on an interconnecting thick or thin film circuit or a printed circuit board. Typically a hybird circuit may comprise a number of monolithic circuit modules mounted together with discrete components on a thick film circuit which has been formed on a ceramic substrate with the input and output connections to the hybird circuit being formed on the edges of the ceramic substrate.

Such a hybird circuit can be mounted in a supporting frame having electrical contacts which connect with the edges of the substrate to make electrical connection thereto and these contacts can be soldered when the substrate is in place.

Demounting of such a hybird circuit requires heating of the soldered contacts to melt the soldered joints before the hybird circuit can be removed. In practice a complex hybird circuit will have many edge connections and, due to the need to miniaturise components in much of modern electronic equipment it may be necessary to dispose the connections around all the edges of, say, a rectangular substrate.

According to the invention there is provided a soldering tool for a hybird circuit as hereinbefore defined comprising a pair of electrically conducting members in fixed relationship to and insulated from each other and a plurality of electrically conducting heating elements each of which is electrically connected between the two members, the elements being arranged so as to make contact each with a plurality of electrical contacts which are solderable to the edge connections of the hybird circuit.

According to one embodiment of the invention a soldering tool for a hybird circuit as hereinbefore defined comprises a pair of rectangular low impedance electrically conducting plates spaced apart by a sheet of insulating material, two pairs of high impedance electrical heating elements arranged on one side of the pair of plates, the heating elements being disposed all at the same distance from the nearest plate and defining an area beneath said plate corresponding to the shape of the plate, each adjacent pair of heating elements being electrically connected at their adjacent ends to the corner of one plate and at their other ends to the opposing corners of the other plate, and means for electrically connecting the two plates of the two poles of a source of electric current.

In order that the invention may be more readily understood an embodiment will be described with reference to the accompanying drawings, in which: Fig. 1 illustrates the method of mounting a hybird circuit, and Fig. 2 illustrates a soldering tool.

The hybird circuit 1 (Fig. 1 ) comprises a rectangular substrate, e.g. of ceramic material, bearing on at least one face a circuit pattern (not shown) which terminates in a plurality of solderable edge connections 2 disposed on some or all of the edges of the substrate. The hybird circuit is mounted by locating the substrate on a rectangular frame 3 which carries a corresponding plurality of solderable spring contacts 4. Each contact 4 comprises an inner contact portion 4a, which is to be soldered to the corresponding substrate connection, and an outer contact portion 4b which is designed to transmit both heat and pressure to the inner contact portion 4a during the soldering operation. The frame 3 is carried on a base board 5, through which the stem 4c of the contact protrudes to enable a wiring connection to be made thereto.

The soldering operation is effected with the aid of a soldering tool 6 which applies heat and pressure to all the contacts simultaneously.

The soldering tool shown in Fig. 2 comprises two rectangular metal plates 20, 21, made of copper for example, which are sandwiched together with an intervening layer 22 of an insulating material, e.g. a sheet of plastics material, and secured with nylon screws and nuts 23. As shown both metal plates each have one pair of opposing corners 24 cut off diagonally, the cut corners of one plate being oriented with the uncut corners of the other plate. The uncut corners 25 of each plates have an angle bracket 26 affixed thereto, the brackets being made of copper and all extending in the same direction from the plates. (Although it is necessary to cut the corners of one plate only to provide a clearance for the brackets of the other plate it is easy and convenient to make both plates identical).The pair of brackets on each plate differs in length by the thickness of one plate so that the free ends of all the brackets are in the same plane parallel to that of the plates.

Between each pair of adjacent brackets there is secured a heating element 27 which is a brass or copper bar so shaped to provide a relatively high impedance when compared with that of the plates 20, 21. Each plate has one large hole 28 and one small hole 29, the large hole on one plate being concentric with the small hole on the other plate. Each large hole provides clearance for affixing an electric current conductor to the small hole in the other plate, the two conductors (not shown) being connected to an electric power source. When a high current is passed through the tool the four heating elements become hot simultaneously, due to their relatively high impedance, whereas the plates remain substantially cooler than the heating elements.

In use the hybird circuit is first placed in position on its supporting frame and the soldering tool is then pushed down so that the heating elements make contact with all the outer contact portions 4b simultaneously.

Claims

1. A soldering tool for a hybird circuit as hereinbefore defined comprising a pair of electrically conducting members in fixed relationship to and insulated from each other and a plurality of electrically conducting heating elements each of which is electrically connected between the two members, the elements being arranged so as to make contact each with a plurality of electrical contacts which are solderable to the edge connections of the hybird circuit.

2. A soldering tool for a hybird circuit as hereinbefore defined comprises a pair of rectangular low impedance electrically conducting plates spaced apart by a sheet of insulating material, two pairs of high impedance electrical heating elements arranged on one side of the pair of plates, the heating elements being disposed all at the same distance from the nearest plate and defining an area beneath said plate corresponding to the shape of the plate, each adjacent pair of heating elements being electrically connected at their adjacent ends to the corner of one plate and at their other ends to the opposing corners of the other plate, and means for electrically connecting the two plates to the two poles of a source of electric current.

3. A soldering tool substantially as described with reference to Fig. 2 of the accompanying drawings.