GB2309834A - Terminal pins for printed circuit boards - Google Patents

Abstract

An electrically conductive sheet 1 eg for use as part of a frame in a device such as a tuner or modulator, is preformed with a plurality of integral pins 10 which are bent outwardly from the sheet and their distal ends secured in through holes 5 of a printed circuit board 2 to electrically interconnect the pins with the board circuit. The other ends of the pins are then severed from the sheet so as to obtain a plurality of free terminal pins on the circuit board. The board can then be inverted and placed into position on the remaining part of the frame so that the terminal pins extend outwardly from the frame cut outs and are useful as terminal pins. The sheet material 1 is precoated with solder before pin formation and, so as to ensure maximum solder coating of the pin surface areas, may be indented with narrowed portions (19, figure 6) between the areas where pins are to be formed, followed by the solder coating.

Description

TERMINAL PINS FOR PRINTED CIRCUIT BOARDS This invention relates to terminal pins for printed circuit boards.

Printed circuit boards are often provided with a plurality of terminal pins which are used to connect the circuit arrangement mounted upon the board with external circuits. These boards are often mounted inside frames when they form part of an apparatus which can form part of another apparatus, for example a tuner or a modulator forming part of a television set or video recorder. As shown in Figure 1, the printed circuit board 2 sits inside a metal frame 1 in such a way that a plurality of terminal pins 3, electrically linked to the circuit on the board, protrude out of the frame through a cut-out 6 so that the unit can be easily attached to other parts of the television set or video recorder. If it is required to replace or service the modulator or tuner for example it is a simple matter to disconnect the terminal pins and remove the frame assembly with circuit board.

Terminal pins are generally individually formed of, for example, tin plate and individually inserted into an insulating block 4 such that the required number of pins extends from the block. An end of each pin extends through the block such that it can be extended through a respective through hole 5 on a board and soldered into place on the board when the block is brought into the vicinity of the board.

Since the number of pins on a terminal block will vary, this approach necessitates the assembly of a number of different sized terminal blocks with different numbers of different pins and also of course involves the manufacture of individual pins. Furthermore, since the pins have to protrude from the side of a box such as frame 1 there is an inevitably a wastage in material when portions 6 are cut out of the frame and these portions are generally discarded. In a large scale operation, the amount of material that is discarded can be significant.

The present invention arose in an attempt to provide an improved method and apparatus of assembling and connecting terminal pins to printed circuit boards and is applicable to terminal pins used on a variety of printed circuit boards.

According to the present invention there is provided a method of forming terminal pins on a printed circuit board, comprising forming a sheet of electrically conductive material with a plurality of elongate integral pin portions, inserting distal ends of the pin portions into corresponding terminal holes on a printed circuit board; securing the pins in the holes to electrically interconnect them with the circuit on the board; and severing the other ends of the pins from the frame.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a previously proposed circuit board and terminal pin design; Figure 2 shows a frame member constructed in accordance with an embodiment of the invention; Figure 3 shows a method of attaching terminal pins to a printed circuit board; Figure 4 shows the apparatus of Figure 3 after the pins have been cut; Figure 5 shows a cross-section of a frame wall; Figure 6 shows a cross-section of a modified frame wall; Figure 7 shows a cross-section through a pin formed from the wall of Figure 5; and Figure 8 shows a cross-section through a pin formed from the wall of Figure 6.

Referring to Figure 2, there is shown one panel of a frame for an electrical unit such as a modulator or tuner. The frame is formed of solder-coated steel and is cut, as shown, to form a plurality of recessed pins 10 in a desired configuration. Each pin comprises a first elongate portion 11 integral with the body of the frame, a second, widened portion 12 and a distal tapered portion 13. The pins may of course be made in other shapes as appropriate. It is important to note, however, that the pins form an integral part of the frame and the spaces between them are cut or otherwise removed from the frame material. The pins sit in the recesses 14,15 which would normally be formed in the frame. They may extend beyond the lower extent of the frame if necessary.

The pins are then bent outwards from the frame, as shown in Figure 3 such that portions 11 and 12 extend at approximately 90" (which angle may be varied) to the plane of the frame and the distal tapered portions 13 extend generally parallel to the plane of the frame.

These angles may be varied depending on circumstance. The pins thereby extend outwardly from the plane of the frame.

A circuit board 2 is predrilled with a required plurality of through holes 5, corresponding to the number and spacing of pins 10. The holes will normally be through plated with a conductive material and electrically interconnected to the circuits on the board. The board is then placed on top of the tapered ends 13 of the pins such that each of the ends extends through a respective through hole 5 of the board. Each of the pin members can then be secured to the board, eg by heating to allow the solder coating to flow. Each pin is then removed, eg by cutting at its base, from the frame member and this is shown in Figure 4.The resulting board 2 is provided with a plurality of terminal pins which extend outward in the correct disposition from the board, the terminal pins having been cut from the frame which, since it no longer has any pin portion projecting from it, becomes a standard frame member.

Since each of the pin members is integral initially with the frame, they are already supported when the printed circuit board is placed into position and the pins soldered to the board. Thus, it may be simpler and easier to connect a circuit board with embodiments of the present invention then by having to individually locate and secure a number of free pins as in prior art. The required number and spacing of pins is also automatically determined for respective circuit boards and frames.

The circuit board with the pins attached and their ends cut from the frame, can then be placed upon a completed frame and secured into place. This will normally involve inversion of the circuit board with respect to the frame such that each plurality of terminal pins locates into a respective slot on the frame. The resulting component has a frame member with a circuit board sitting inside it, and a plurality of terminal pins extending outwards from the circuit board and is therefore effectively the same as prior art components of this type. Thus, ends 11 of each terminal pin form the distal ends of the pins of the finished component, for connection to external apparatus.

The frame member from which the pins were originally cut can form part of the final component, or the pins may be cut from a different frame member.

The frame members are generally formed of solder-coated steel and therefore the terminals in embodiments of the invention are also formed of this. The frames may alternatively be formed of other materials.

It is simpler to coat a steel blank with solder material before cutting out the frame shape and thereby the pins, rather than trying to apply the solder after cutting. Hence, before the pins are formed, the cross section through the steel blank is as shown in Figure 5 comprising a central planar sheet of steel 14 and an outer coating on each surface of solder 15. A problem may arise, however, in that when the pins are formed by cutting, the resulting pins have the cross-section shown in Figure 7 in which most of the side parts of the pins 16 have no solder coating. The solder coating is substantially only on the front and rear of the pin (although a small amount may seep onto part of the side by the cutting action).Thus, when the pin is soldered to a circuit board, that is, when the pin is inserted and heated to melt the solder, the solder may not extend all the way round each pin and therefore incomplete soldering could occur. This may tend to weaken the solder joint and may result in malfunction or detachment of the pins in extreme examples.

In preferred embodiments of the present invention, this effect may be considerably reduced by shaping the steel blank before solder coating and before cutting. One example of a shaping is shown in Figures 6 and 8. In Figure 6, the blank is narrowed at portions 17 corresponding to spaces between where pins will be formed.

This may be done by applying cooperating dies to the steel plate. A typical dye is shown at 18. The pins are then cut by cutting away these narrowed portions, eg at each pair of lines 19 on the figure. The cutting is of course done after the blank of Figure 6 has been coated with solder. The resulting shape of each pin is as shown in Figure 8. It is clear from this figure that, although the solder does not extend completely around each pin it extends further round then in the pin of Figure 7 and thus better soldering quality should be obtained with less risk of detachment or malfunction. The blank may be shaped to form pins of other shapes, eg arcuate shapes, for example where necessary.

Alternatively the frame with its associated pins preformed may be solder coated after forming the pins.

This is, however, less satisfactory and involves greater expense and effort.

Claims (10)

1. A method of forming terminal pins on a printed circuit board, comprising forming a sheet of electrically conductive material with a plurality of elongate integral pin portions, inserting distal ends of the pin portions into corresponding terminal holes on a printed circuit board; securing the pins in the holes to electrically interconnect them with the circuit on the board; and severing the other ends of the pins from the frame.

2. A method as claimed in Claim 1, wherein the pin portions are bent outwardly from the blank before securing to the holes.

3. A method as claimed in Claim 1 or Claim 2, wherein the sheet forms part of a frame of an electronic module.

4. A method as claimed in Claim 3, wherein the module is a tuner, a modulator, an i.f. unit, a NICAM unit or a combined unit incorporating one or more of these components.

5. A method as claimed in Claim 4, wherein, after severing, the board is inverted with respect to the sheet and secured in place on the frame, with the pins protruding therefrom to act as terminal pins.

6. A method as claimed in any one of preceding claims, wherein the sheet, before formation of the pins, is shaped to have a variable cross-section.

7. A method as claimed in Claim 6, wherein the sheet is shaped to have narrowed portions adjacent to the portions where pins are to be formed.

8. A method as claimed in Claim 7, wherein the sheet is coated with a material before formation of the pins.

9. A method as claimed in Claim 8, wherein the material is solder coating.

10. A method of forming terminal pins substantially as hereinbefore described with reference to, and as illustrated by, the accompanying drawings.