GB2276281A - P.c.b. test apparatus - Google Patents

Abstract

A testing apparatus for testing circuit boards comprising a support member supporting at least part of a testing means, the support member having a cross-section of a substantially C-shape along its whole width. The apparatus may include a two-stroke pneumatic test actuator (14) moving a test platen (18) located by guides (20). Actuation is initiated by pressing buttons 24, 26 which are far enough apart as to prevent single-handed operation. <IMAGE>

Description

TESTING APPARATUS FOR PRINTED CIRCUIT BOARDS AND THE LIKE This invention relates to apparatus for the testing of high density bare boards with surface mount technology.

Prior art testing equipment is extremely complicated in design, and can be dangerous and/or difficult to use.

It is an object of the invention to overcome this problem.

In accordance with the invention, a testing apparatus for high density bare boards with surface mount technology (SMT) is substantially C-shaped in cross-section about its whole width.

Such an arrangement allows the operator of the apparatus easy access through the front of the apparatus, and both sides of the apparatus. As a result, bare boards can be tested at much greater speed than prior art arrangements leading to much greater efficiency.

Suitably the apparatus uses a pneumatic system for bringing testing means against an article to be tested, and suitably such is a two-stroke pneumatic system. In particular, the two-stroke pneumatic system comprises moving the testing means quickly upto just before the article is to be tested, and then slowly such that the testing means comes into contact with the article to be tested.

Suitably the pneumatic system is supported by four support members positioned therearound in order to provide accuracy when testing, and in particular to bring the testing means accurately against the article to be tested.

Preferably the apparatus is provided with a two-button means for operating the apparatus, the two buttons being positioned more than a hand width apart from each other so that the operator has to press both buttons, one with each hand, in order to operate the apparatus. This provides a fail-safe safety feature, since the operator's hands cannot be within the apparatus, when the apparatus is operated.

Suitably the mounting plate for the pneumatic system is provided with a sprung brush support system in order to provide a better connection.

Preferably the testing means includes an upper testing plate arrangement comprising at least one (and more preferably two) plate(s) mounted in parallel, and a lower testing plate on which the article to be tested is placed.

The invention will now be described with reference to the accompanying drawings in which: Figure 1 is an exploded view of a first embodiment of testing apparatus in accordance with the invention showing the various pneumatic components of the apparatus; Figure 2 is a further perspective view similar to that of Figure 1 showing the main machine parts of the testing apparatus of Figure 1; Figure 3 is an enlarged side cross-sectional view of a portion of the apparatus of Figures 1 and 2; Figure 4 is a circuit diagram showing the pneumatic control system used with the testing apparatus of Figures 1 to 3; Figure 5 is a perspective view of a second embodiment of testing apparatus in accordance with the invention; and Figure 6 is an enlarged side cross-sectional view of a portion of the apparatus of Figure 5.

A testing apparatus 10 having a testing area 12 for high density bare boards with SMT is shown in Figures 1 to 4.

In particular, Figure 1 shows the outline of the testing apparatus 10 having a substantially C-shaped cross-section (as seen from the left-hand side) along its whole width (see A) such that an operator can place their hand into the front and/or sides of apparatus, thereby achieving easy access to the testing area 12 of the apparatus.

The apparatus 10 can also be described as having a "Clamp-shell profile" as well as C-shaped.

The various pneumatic components of the apparatus 10 are shown in Figure 1 basically comprising a pneumatic cylinder 14 which is mounted on the top of the apparatus at its centre. In particular, the cylinder 10 is mounted to an upper plate 16 which is fixed to the top of the apparatus 10.

In Figure 2, a movable intermediate plate 18 is shown attached to the piston rod 19 (see Figure 1) of the pneumatic cylinder 14, which movable plate 18 is fixed in a vertical sense relative the upper plate 16 by four supporting columns 20 in the form of iron rods positioned about the pneumatic cylinder 14 in order to accurately move the intermediate plate 18 upwards and downwards.

The four columns 20 are movable relative the upper plate 16 within four bronze brushings 21 (two of which are not shown in Figure 2) mounted on the plate 16 and which provide a no-twist downward motion for the plate 18. The intermediate plate 18 comes into contact with a lower plate 22 on which the article to be tested is placed.

The apparatus 10 is operated by two buttons 24 and 26 which are mounted at the front of the apparatus, the buttons being mounted at least a hand distance away from each other.

The button arrangement is such that the intermediate plate 18 and lower plate 22 will only come together when both buttons 24 and 26 are pressed together. Since the two buttons are a hand distance away from each other, the operator has to use both their hands in order to push the two buttons, and thereby operate the apparatus, thus providing a fail-safe safety feature since the operator's hands will not be between the plates 18 and 22 at the time of operation.

The front of the apparatus is also provided with an emergency reset button 27 in addition to the two operating buttons 24 and 26 in order to release the plates 18 and 22 when together.

The upper plate 16 is fixed to each of the four bronze brushings 21 by means of a spring mounted shoulder type bolt 28 which is shown in Figure 3. In particular, it will be noted that a spring 30 is provided between the lower surface of the head 32 of the bolt and the upper surface 34 of the upper plate 16, and that the bolt 28 is secured directly to each bronze brushing 21. This securely fixes the upper plate 16 relative to the brushings 21, however, provides for slight tolerances in the bolt 28 itself.

In Figure 4, a pneumatic circuit diagram for operation of the cylinder 14 is shown. In particular, such achieves duel speed stroking, in other words, the pneumatic cylinder 14 moves the intermediate plate 18 quickly upto just before the testing lower plate 22 and the article to be tested, and then there is second slower stroking so that the plates 18 and 22 come into actual contact with each other at much lower speed, thereby preventing damage to the article to be tested. This two-stroke arrangement is simple yet effective, and limits damage during testing.

Such is particularly used for accurately testing small and dense surface mount technology pads. The speed and length of stroking is also adjustable depending on each surface mount technology pad used.

The circuit diagram shown in Figure 4 includes an optional automatic conductive rubber testing facility (ACRT), further details of which will be ascertained from GB Patent Application No.

9206068.0, the contents of which are incorporated herein by way of reference.

In Figure 5 a testing apparatus 50 is shown similar to that shown in Figures 1 to 4, except that instead of the single upper plate 16 of the apparatus 10 shown in Figures 1 to 4, a two fixed upper plate system 51 is provided in order to provide greater accuracy.

In particular, Figure 6 shows that there are two parallel plates 52 and 54, and the four support columns 20 are guided by eight bronze brushings 56 mounted on the plates 52 and 54, instead of the four bronze brushings 21 shown in the apparatus of Figures 1 to 4. The eight bronze brushings 56 co-operate with each other to provide no twist downward motion for the intermediate plate 18, and in particular, more precise motion for the intermediate plate 18. This brings the unexpected displacement of the plates 18 and 22 to virtually zero.

Eight clamping screws 58 (four to connect the plate 52 to the upper plate 16) are also provided for easier release and fastening of the plate system 51, and also the two plates 52 and 54 are mounted together by fixing guide pins 60 with steel brushes 62, which minimises the set-up time for the plate system 51.

The apparatus is suitable to test all types of bare printed circuit boards including single-sided, double-sided, multilayer boards and panels.

Such arrangements provide for simple, yet effective and safe testing.

Claims (18)

CLAIMS:

1. A testing apparatus for testing circuit boards comprising a support member supporting at least part of a testing means, the support member having a cross-section of a substantially C-shape along its whole width.

2. A testing apparatus as claimed in claim 1 wherein the testing means includes a testing plate.

3. A testing apparatus as claimed in claim 2 further comprising abutment means for abutting the testing plate against an article to be tested.

4. A testing apparatus as claimed in claim 3, wherein the abutment means comprises a pneumatic system.

5. A testing apparatus as claimed in claim 3 or claim 4, wherein the abutment means comprises a two-stroke pneumatic system.

6. A testing apparatus as claimed in claim 5 wherein the first stroke of the pneumatic system is at high speed and the second stroke at low speed.

7. A testing apparatus as claimed in claim 5 or claim 6 wherein the first stroke of the pneumatic system brings the testing plate close to the article to be tested and the second stroke abuts the testing plate against article to be tested.

8. A testing apparatus as claimed in any one of claims 2-6, further comprising guide means to guide the testing plate towards the article to be tested.

9. A testing apparatus as claimed in any one of claims 1-8, wherein the support member comprises at least one fixed upper support surface.

10. A testing apparatus as claimed in any one of claims 1-9, wherein the support member comprises two upper support surfaces arranged in substantially parallel planes.

11. A testing apparatus as claimed in any one of claims 1-10, wherein the support member comprises a lower testing surface, on which an article to be tested may be placed.

12. A testing apparatus as claimed in claim 11, wherein the testing surface is in a plane substantially parallel to the support surface or surfaces.

13. A testing apparatus as claimed in any one of claims 8-12 wherein the guide means comprises a plurality of guide rods each engageable with fixed bushings; the guide rods being attached to the testing plate, and the bushings being mounted on the support surface or surfaces.

14. A testing apparatus as claimed in claim 13, wherein the bushings are attached to the support means by an attachment member comprising a head; a shaft; and a spring; the shaft passing through the support member; and the spring being positioned between the support member and the head.

15. A testing apparatus as claimed in claim 14, wherein the shaft of the attachment member further comprises an annular shoulder above which is formed a first section of the shaft and below which is formed a second section of the shaft which is screwthreaded, wherein the first section of the shaft passes through the support member and the second section of the shaft engages with a bushing.

16. A testing apparatus as claimed in any one of claims 8-15, wherein the bushings surround an aperture in the support surface or surfaces.

17. A testing apparatus as claimed in any one of claims 1-16 wherein the apparatus is operable by simultaneously pressing two buttons on the apparatus which are placed more than one hand width apart.

18. A testing apparatus substantially as herein described with reference to any embodiment shown in the accompanying drawings.