GB2219443A

GB2219443A - Forming mechanical and electrical connections of films to printed circuit boards

Info

Publication number: GB2219443A
Application number: GB8907732A
Authority: GB
Inventors: Richard Brown
Original assignee: PENNWALT PIEZO FILM
Current assignee: PENNWALT PIEZO FILM
Priority date: 1988-04-08
Filing date: 1989-04-06
Publication date: 1989-12-06
Anticipated expiration: 2009-04-06
Also published as: GB2219443B; GB8907732D0; GB8808212D0

Abstract

A metalised piezoelectric polymer film (10, 12, 14) is electrically and mechanically connected to a printed circuit board (pcb) (28). A hole (34, 36) is formed through the pcb so as to pass through a track (46) thereon and a hole is also formed through a metallized portion of the film. The holes are then aligned and the component is secured to the pcb by a conductive fastener (eg bolt (38a, 38b)) passing through the aligned holes. Alternatively, a rivet may be used instead of the bolt. <IMAGE>

Description

"Forming Mechanical and Electrical Connections to Printed Circuit Boards" This invention relates to a method of obtaining both mechanical securement and electrical connection between a printed circuit board (pcb) and an associated component.

The invention is particularly, but not exclusively, relevant to the mounting on a pcb of a film carrying metallized electrodes or conductors on both sides. The film may, for example, be of polymeric piezoelectric material such as polyivinylidene fluoride (PVDF). One application of the present invention is in the manufacture of a vibration (8907733~3 > sensor described in our copending applicationlfiled concurrently herewith, where a PVDF film is secured to a strip of spring material and this assembly is cantilevered from a pcb.

In this and other applications where both a mechanical and an electrical connection is necessary, it would hitherto have been necessary to make the mechanical connection by mechanical fasteners such as screws or rivets and the electrical connection separately. The invention, which is defined in the appended Claims, has as one object the provision of a means of doing both simultaneously.

An embodiment of the invention will now be described, by way of example only, with reference to the drawings, in which: Fig. 1 is an exploded perspective view of a laminar assembly to be secured to a pcb; and Fig. 2 is an enlarged cross-sectional view of the assembly secured to the pcb.

The assembly of Fig. 1 comprises a strip 10 of phosphor bronze to which is secured a PVDF film 12 by means of double-sided adhesive tape 14. The film 12 is provided on its opposed faces with metallized electrodes, the upper being seen at 16. This electrode 16 has a projecting connector portion 16'. The lower electrode has a similar connector portion 18'. The assembly must be secured to a pcb and the portions 16' and 18' electrically connected to separate tracks thereon, preferably on the same side of the pcb.

It will be noted from Fig. 1 that holes 20 and 22 are punched through the film 12 and through the connector portions 16' and 18' respectively; the holes 20, 22 being of equal size. Also, holes 24 and 26 are punched through the strip 10 in such positions that, when assembled, these are in registry with holes 20, 22; the holes 24, 26 in strip 10, however, are of unequal size. An area of tape 14 in alignment with the hole 22, 26 and connector portion 18' is removed.

Turning to Fig. 2, a pcb 28 has tracks 30, 32 on one surface. Holes 34, 36 are drilled through the pcb 28 and tracks 30, 32, the holes 34,36 being of equal diameter to the holes 20,22 and 26. The assembly of Fig. 1 is positioned against the face of the pcb 28 opposite the tracks 30, 32 with the various holes in registry, and secured in position by bolts 38, nuts 40 and washers 42 and 44. This effects mechanical attachment, and also electrical connection. The connector portion 16' is conductively coupled to track 30 via washer 42a, bolt 38a, and washer 44a. Connection between track 32 and connector portion 18' is via washer 44b and bolt 38b. This, may be sufficient, relying on contact between the portion 18' and the side of bolt 38b, alternatively, as shown, a small piece of copper foil 46 may be folded around the edge of pcb 28 to provide a conductive path via strip 10 by virtue of the missing portion of the adhesive tape 14.

Where the copper foil 46 is used, it preferably passes under the heads of both bolts 38, and adjacent bolt 38a is apertured to the same size as hole 24 so as to leave a clearance between these items and bolt 38a.

Instead of bolts and nuts, rivets may be used as the fastners, with or without interposed washers. By using rivets with a suitable jig and rivetting punch, very rapid assembly can be achieved.

Claims

1. A method of electrically and mechanically connecting a component comprising a metallized film to a printed circuit board (pcb), comprising forming a hole through the pcb so as to pass through a track thereon, forming a hole through a metallized portion of the film, aligning said holes, and securing the component to the pcb by a conductive fastener passing through the aligned holes.

2. A method of manufacturing an electrical device, comprising the steps of: forming metallized layers on the opposed faces of a plastics film, the metallized layers including respective connector portions adjacent one edge of the film, the connector portions being out of alignment with each other; forming first and second holes through the film, each passing through a respective connector portion; providing a substrate having third and fourth holes adjacent one edge thereof on the same centres as said first and second holes; securing the film to the substrate with the first and third holes and the second and fourth holes in alignment by adhesive means interposed between the facing surfaces of the film and the strip except in the vicinity of the first and third holes;; providing a pcb having first and second tracks for electrical connection to respective ones of the connector portions; forming fifth and sixth holes passing through the pcb and through the first and second tracks, respectively; positioning the assembly of film and substrate against the face of the pcb remote from the tracks such that the first, third and fifth holes and the second, fourth and sixth holes are in registry; and fastening electrically conductive mechanical fasteners through each set of aligned holes.

3. The method of Claim 2, in which a flexible electrically conductive member is passed around the edge of the pcb so as to be interposed between the substrate and the adjacent face of the pcb, and between the fastener and the second track, the substrate being electrically conductive.

4. The method of Claim 3, in which the flexible conductive member is also interposed between the substrate and the pcb in the vicinity of the fifth hole, the flexible conductive member is formed with a seventh hole in that vicinity, and the third and seventh holes are larger than the diameter of the fastener passing therethrough so as to provide an insulating clearance.