MACHINE FOR THE ELECTRIC TEST OF PRINTED CIRCUITS WITH ADJUSTABLE POSITION OF THE SOUND NEEDLES

Abstract: Machine for the electric test of printed ciruits, of the type comprising a board which bears (1) a plurality of conductive needles (10) which are connectable on their reverse side with means for the analysis of the electric parameters between one and the other needle, characterized in that: at least two coplanar needle boards and one adjacent to the other (1SS-1SD/1IS-1ID) are used, and one board (1SS/1IS) is made movable with respect to the other (1SD/1ID), and the respective board to be checked (2) is made movable with respect to said boards (1) or vice-versa.

Description: 1 DESCRIPTION 2 MACHINE FOR THE ELECTRIC TEST OF PRINTED CIRCUITS 3 WITH ADJUSTABLE POSITION OF THE SOUND NEEDLES. 4 Technical Field 5 This invention has for object a machine for the electrical test of 6 printed circuits with adjustable position of the sound needles. 7 Background Art 8 In prior art machines for the checking of printed circuits are 9 kn o w n . I 0 These machines generally are endowed of a board or bed that bears I I a plurality of electrically conductive needles, on which is placed 1 2 the printed circuit card and by suitably activating the electric 1 3 conductivity among the different needles and by taking the 1 4 respective measuπngs it is possible to check whether or not the 1 5 printed circuit has some defects. 1 6 Obviously for such check it is necessary for the needles to contact 1 7 the printed circuit in the suitable position 1 8 As the printed circuits are very different, it is necessary to apply 1 9 over the base needle board, an adaptation board that comprises the 2 0 same needles but displaced in a different way according to the 2 1 pπnted circuit to be checked. 2 2 The drawback of this solution is in the limits of the machine and in 2 3 the possibility of checking only the pπnted circuits for which are 2 4 available corresponding adapters or adapting boards. 2 5 Requiring as many adapting boards as are the cards with different 2 6 printed circuits to be checked 2 7 Furthermore it is known that the surfaces of the circuits are not 2 8 always coplanar, wheretore it is not alwavs ensured a suitable electric conduction for an effective contact. Another solution provides to make movable that is adjustable the respective sound needles one respect to the other, but this solution is extremely complex and expensive. The latter solution requires also long checking times because a great number of movable needles cannot be available, wherefore there must practically be a check of each circuit. Disclosure of Invention The purpose of the present invention is that of obviating the above-mentioned drawbacks, and in particular of allowing the making of a machine able to check the universal printed circuits, that is by means of a detection conductive needles system that can be adapted to any circuit type. This and other purposes are reached as claimed by means of a machine for the electrical test of printed circuits, of the type comprising a board which bears a plurality of conductive needles that are connectable on their reverse side to means for the analysis of the electrical parameters between one and the other needle, characterised in that: - are used at least two coplanar needle boards one adjacent to the other, and - one board is made movable respect to the other, and - the respective card to be checked is made movable respect to said at least two boards or vice-versa. In this way there is the immediate advantage of simplifying the whole system by making universal the application of the machine to different printed circuits without need for adapters. In fact by this it is possible to activate one board needle in any position of the circuit leading end and to activate an opposite needle of the opposite board, which thanks to the movability of the same board can reach any determined circuit end point to be tested independently of its position, place and shape. In this way the universalization of the testing system for any card is ensured. In fact: - when the printed circuit opposite points to be checked lie one under the first and the other under the second board, and do not coincide with the sound needles, it is sufficient to move both the first and the second board (or move also the card) to position them in exact correspondence with the opposite points to be checked; - when the two printed circuit opposite points to be checked are so close to be covered by just one board, it is sufficient to move the card to be checked with said circuit to an exactly intermediate position between said two boards (or vice-versa to move both said boards), so that one point of the circuit lies under the first plate and the other lies under the second board, and then by moving both of them it will be possible to make perfectly coincide said two points with one respective needle from each of said two boards. Advantageously the needle boards are set both over and under the card to be checked so that this latter is placed between them. In this way it is obtained a greater universalization of use. Advantageously the machine comprises also the characteristic that the detection needles are axially movable. In this way, out of a plurality of needles in a board it is possible to make interact only some of them, centring with greater ease the wished positions of the printed circuit. Further advantage derives in that by the axial movability of the needles it is possible to contact better the respective wished points of the circuit even if the card or the circuit surface is not perfectly coplanar in all its points. Advantageously the needles are made axially movable by electromagnetic means. In this way the desired needle is made operate in a safe and simple way . These and other advantages will appear from the following description of preferred embodiment solutions with the help of the included drawings whose details are not to be considered limitative but only supplied 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 couples of opposite detection boards movable one respect to the other and having the card to be checked set between them. The detection boards are indicated by 1 while the needles are indicated by 10. In particular in the Figures the two upper respectively right and left couples of testing detection boards are indicated by ISS and ISD and the lower respectively right and left ones by IIS and 1ID. Each board has a plurality of needles axially movable 10 by electromagnet 1 1. Each needle is electrically connected to a prior art system for the electric parameters checking 12. All the boards are as said movable one respect to the other for operative positioning. The card placed between these is indicated by 2 and it is also movable on the plane. The system provides a checking by a net list "net-list" with relative positions of single points. The connections test is carried out from point to point, so that for testing the connections of a net made of n points, are necessary n - 1 tests between couples of selected points in order to cover all the connections . The short circuit test among different nets, is carried out by selecting one point out of each couple of nets. The maximum number for testing (proving) in this way n nets, can be calculated by the following formula: n * ( n - l ) / 2 This number can be decreased by selecting only close nets, namely those that are close one to the other within a predetermined range. The positions to be tested are underdivided in sectors corresponding to the number of needles in the movable board (bed), so that the point to be tested can be reached by the position and by one of the testing needles. After the points to be tested are reached by at least two boards, it is necessary to check the connection or the insulation. To diminish the time used for movements, it is possible to optimize the paths of the axes, modifying the single tests frequency. The machine consists of the frame to which are fixed two couples of opposite boards and independently, movable respect to the two orthogonal axes. On the boards are fixed the testing sounds (needles) directly operated in their axial movement by electromagnet. At first, the printed circuit is placed on a bearing frame that transports it between the two boards. In this position the card remains fixed or in its turn may be furtherly moved. The boards are put close to the card and the test begins. Each board is checked and operated independently, 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 couple of simultaneously operated sounds it is possible to check 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 wished to. As said, besides the movability of one board respect to the other of each couple, it is preferable that also the card bearing is movable respect to one or to the other couple of boards. In this way a greater universalization of use is obtained.

Claims: Claims 1. Machine for the electric test of printed circuits, of the type including a board which bears (1 ) a plurality of conductive needles ( 10) that are connectable on their reverse side to means for the analysis of the electric parameters between one and the other needle, characterised in that: - are used at least two coplanar needle boards and one adjacent to the other ( ISS- ISD / 1IS-1ID) and, - one board (1 SS/1 IS) is made movable respect to the other ( 1SD/1ID), and - the respective card to be checked (2) is made movable respect to said boards (1 ) or vice-versa. 2. Machine for the electric test of printed circuits according to claim 1 , characterised in that it utilizes two coplanar adjacent test boards (1 ) movable one respect to the other. 3. Machine for the electric test of printed circuits according to claim 1 , characterised in that it utilizes two couples of opposite test boards ((ISS- ISD / 1IS-1ID). 4. Machine for the electric test of printed circuits according to claim 1 , characterised in that said needles (10) are made axially movable . 5. Machine according to previous claim, characterised in that the movability of said needles is obtained by electromagnetic means ( 1 1 ). 6. Machine according to any one of the previous claims, characterised in that it is made so to operate in the testing between two points of a circuit acting with one needle of a board on one side and with one needle of another board on the other, after having carried out a respective centring movement of the one respect to the other and/or of both of them respect to the card circuit or vice- versa.

Inventors: FUMO CESARE, VODOPIVEC JOZEF, FUMO, CESARE, VODOPIVEC, JOZEF
Applicants: FUMO CESARE, NEW SYSTEM SRL, VODOPIVEC JOZEF, FUMO, CESARE, NEW SYSTEM S.R.L., VODOPIVEC, JOZEF
Application year: 1996
Main classification: G01R1
IPC codes: G01R1, G01R31, H05K1, H05K13