WO1997011378A1

WO1997011378A1 - Machine for the control of printed circuits

Info

Publication number: WO1997011378A1
Application number: PCT/IT1996/000091
Authority: WO
Inventors: Jozef Vodopivec; Cesare Fumo
Original assignee: New System S.R.L.
Priority date: 1995-09-22
Filing date: 1996-05-03
Publication date: 1997-03-27
Also published as: AU5513596A; IT1282828B1; ITUD950182A1; ITUD950182A0

Abstract

The object of the invention is to provide a machine for the control of printed circuits, of the type comprising a board (1) bearing a plurality of needles (10) that are connectable on their reverse side to means for the analysis of the electric parameters (12) between one and the other needle, having the substantial characteristic that the detection needles are axially movable (11). In such a way, among a plurality of needles can be made to interact only some of them, by centering more easily the desired positions of the printed circuit.

Description

DESCRIPTION MACHINE FOR THE CONTROL OF PRINTED CIRCUITS Technical Field This invention has for object a machine for the opposite control of printed circuits. The invention finds particular even if not exclusive application in the sector of the control of the printed circuit cards. Background Alt In the prior art machines for the control of the printed circuits are kn o w n . These machines generally consist of a board or bed bearing a plurality of electrically conductive needles, on which must be disposed the card with the printed circuit and by activating properly the electric conductivity among the different needles and by making the respective measurings it is possible to check whether the printed circuit has defects. Obviously for such control it is necessary for the needles to contact the printed circuit in the proper position. As the printed circuits are very different, it results necessary to apply over the needle base board, an adaptation board that comprises the same needles but displaced in a different way in conformity with the printed circuit to be controlled. The drawback of this solution is the limitation of the machine and the possibility to control only the printed circuits that have at disposal corresponding adapters or adaptation boards. Needing as many adaptation boards as are the cards with different printed circuits to be controlled. Furthermore it is known that the layers of the circuits are not always coplanar, wherefore a suitable electric conduction for an effective contact is not always ensured. Disclosure of Invention The purpose of the present invention is that to obviate the above- mentioned drawbacks, and in particular to allow the making of a universal machine able to control the printed circuits, that is having a system of conductive detection needles that can be adapted to any type of circuit . This and other purposes as claimed are obtained by means of a machine for the control of printed circuits, of the type comprising a board bearing a plurality of conductive needles that are connectable on their reverse side to means for the analysis of the electric parameters between one and the other needle, characterized in that said needles are axially movable on control. In this way it is obtained the immediate advantage of simplifying all the system by making universal the application of the machine on different printed circuits and by operating in a simplified way making come out only the needles that at the moment concern the specific circuit. In such a way, among a plurality of needles can be made interact only some of them, by centring more easily the desired positions of the printed circuit. A further advantage derives from that by the axial movability of the needles it is possible to have a better contact with the respective desired points of the circuit even if the card or the layer of the circuit is not perfectly coplanar in all its points. Advantageously the machine comprises some means for moving the needle bearing board respect to the card bearing or vice-versa, and this in such a way to place the concerned needles in exact correspondence to the circuit independently of whether the card position is centred. In this way the use versatility of the machine is better structured and more universalized. Advantageously two of the control boards are opposite and one is movable respect to the other, in this way it is possible to determine any position and distance between the needle of one board respect to the needle of the other one. Advantageously the needles are made axially movable by electromagnetic means. In this way the desired needle is operated in a simple and safe way. These and other advantages will be shown by the following description of embodiment preferred solutions with the help of the included drawings whose details are not to be considered limitative but only given as an example. Figure 1 is a perspective schematic view of a detection board (bed); Figure 2 is a cross-sectional schematic view of an axially movable detection needle. Figure 3 is a cross-sectional view of the preferred embodiment with two opposite detection boards movable one respect to the other and with the card to be controlled placed between them. In particular in the figures the two detection testing boards are indicated by 1 and 1'. Each board has a plurality of needles axially movable 10 by electromagnet 1 1. Each needle is electrically connected to a known art electric parameters control system 12. 1 The opposite boards as mentioned are movable one respect to the

2 other for the operative positioning.

3 The card positioned between these is indicated by 2.

4 The system provides a control by a net list "net-list" with relative

5 positions of single points.

6 The connection test is carried out from point to point, so that for

7 testing the connections of a net made of n points, are necessary n-l

8 tests between pairs of points selected in such a way to cover all the

9 connec tions .

I 0 The test on short circuits among different nets, is made by selecting

I I a point out of each pair of nets.

1 2 The maximum number for testing (testing) n nets in this way, is

1 3 calculated with the following formula:

1 4 n * ( n - l ) / 2 .

1 5 This number can be reduced by selecting only alongside nets, that is

1 6 the ones close to each other in a pre-determined distance.

1 7 The positions to be tested are underdivided in sectors corresponding

1 8 to the number of needles in the movable board (bed), so that the

1 9 point to be tested is reachable with the position and with one of the

2 0 testing needles.

2 1 After the points to be tested are reached, it is necessary to check the

2 2 connection or insulation.

2 3 To shorten the time used for the movements, it is possible to optimize

2 4 the paths of the axes, by modifying the frequency of the single tests.

2 5 The machine is made up of a frame on which are fixed two opposite

2 6 boards and independently, movable respect to the two orthogonal

2 7 axes.

2 8 On the boards are fixed the testing sounds (needles) directly operated by electromagnet in their axial movement. At the beginning, the printed circuit is placed on a bearing frame that transports it between the two boards. In this position the card remains fixed. The boards are put close to the card and the test begins. Each board is independently controlled and operated, so that the maximum stroke necessary is defined by the distance among the sounds . In correct position, the electromagnet operates the sound on the surface to be contacted and thus by a pair of sounds simultaneously operated is controlled the functionality of the circuit among the two desired points, the respective continuity and eventual short circuits. The process proceeds by points in repetitive way as desired. Advantageously also the card bearing may be moved respect to one or the other board. In this way is obtained a wider universalization of use .

Claims

Claims 1. Machine for the control of printed circuits, of the type comprising a board bearing (1 ) a plurality of conductive needles (10) that are connectable on their reverse side to analysis means of the electric parameters ( 12) between one and the other needle, characterized in that said needles are movable on control, axially ( 1 1 )

2. Machine for the control of printed circuits, of the type comprising a board bearing a plurality of conductive needles that are connectable on their reverse side to analysis means of the electric parameters between one and the other needle, according to the characteristics of claim 1., characterized in that: - are used two needle boards ( 1 , 1 ')- one opposing the other and between them is placed for the analysis the respective printed circuit board to be controlled (2), and, - one board is made movable respect to the other at least on its plane.

3. Machine according to the previous claim, characterized in that the movability of said needles is obtained by electromagnetic means ( 1 1 ).