Abstract:
An electrode spacing conversion adaptor is formed of a plurality of sheet elements having top and bottom electrodes arrayed at different intervals along upper and lower ends of each sheet element, respectively, wherein the top electrodes are individually connected to their corresponding bottom electrodes by intermediate conductors. The individual sheet elements are angled such that the upper portions of the sheet elements carrying the top electrodes are stacked at intervals different from intervals at which the lower portions carrying the bottom electrodes are stacked. The individual sheet elements may be stacked to form laminated pieces in such a way that the bottom electrodes are concentrated in a small area while the top electrodes are distributed over a larger area at greater intervals in two horizontal directions. In this construction, the geometric arrangement of any two test points selected on a fine-pitch conductor pattern of a printed wiring board is enlarged at the top electrodes and electrical connections from the test points to external test equipment can be easily established.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an electrode spacing conversion adaptor to be used to properly connect test points on a fine-pitch conductor pattern of a printed wiring board to external test equipment for automatic board testing. 
     2. Discussion of the Related Art 
     For automatic testing of a conductor side of a printed wiring board, it has conventionally been required to connect one or more pairs of test points on the conductor side to an external board tester by using a pair of contact probes. 
     Each contact probe includes a sleeve and a contact pin which is slidably housed in the sleeve and forced toward a far end of the sleeve by a spring fitted in the sleeve. A lead connected to the contact pin emerges from inside the sleeve for external connection. A pair of such spring contact probes directed to the conductor side of the printed wiring board are moved to desired test points and brought into contact therewith, and connections between the test points and the external board tester are established. 
     With printed circuit conductor patterns becoming more and more finely pitched nowadays, a problem often encountered with contact probe technique of the prior art has been that the contact pins of two probes tend to contact each other when probing nearby test points, making it impossible to properly perform the board testing. 
     SUMMARY OF THE INVENTION 
     In view of the aforementioned problem of the prior art, it is an object of the invention to provide an electrode spacing conversion adaptor which facilitates automatic testing of a printed wiring board carrying a fine-pitch conductor pattern. It is a more specific object of the invention to provide an electrode spacing conversion adaptor which is formed by laminating a plurality of angled sheet elements and carries electrodes arranged with different spacings on top and bottom surfaces of the adaptor so that electrical connections can be easily established from nearby test points on a fine-pitch conductor pattern of a printed wiring board to external test equipment. 
     According to a main feature of the invention, an electrode spacing conversion adaptor is formed of a plurality of sheet elements having top and bottom electrodes arrayed at different intervals along upper and lower ends of each sheet element, respectively, wherein the top electrodes are individually connected to their corresponding bottom electrodes by conductors, and the individual sheet elements are angled in such a way that the upper portions carrying the top electrodes are stacked in the direction of the thickness of the sheet elements at intervals different from intervals at which the lower portions carrying the bottom electrodes are stacked. 
     Since the top and bottom electrodes are arrayed at different intervals and the sheet elements are angled such that the upper portions carrying the top electrodes and the lower portions carrying the bottom electrodes can be stacked at different intervals in the direction of their thickness in this construction, the top electrodes are arranged at intervals different from the intervals at which the bottom electrodes are arranged in two horizontal directions when the sheet elements are stacked to form a single structure. More specifically, the sheet elements can be stacked in such a way that the bottom electrodes are arrayed at small intervals and the top electrodes are arranged at large intervals, for example. When the bottom electrodes of the electrode spacing conversion adaptor of this example are positioned in close contact with a conductor pattern of a printed wiring board, test points on the conductor pattern electrically connected to the corresponding top electrodes. Even when individual conductors of the conductor pattern are finely pitched, the geometric arrangement of the test points is enlarged at the top electrodes. This electrode spacing conversion feature of the adaptor makes it easier to connect the printed wiring board to external measuring equipment or to matrix circuit devices for electrical testing between specified test points. 
     In one aspect of the invention, the thickness of the upper portion of each sheet element carrying the top electrodes may be made different from the thickness of the lower portion of each sheet element carrying the bottom electrodes. 
     If the upper portion of each sheet element is formed to a thickness larger than that of the lower portion, for example, the top electrodes can be arranged at larger intervals than the bottom electrodes in the stacking direction of the individual sheet elements, without using any specially made spacers. 
     According to the invention, the electrode spacing conversion adaptor may be produced by laminating the sheet elements into a single laminated piece, or by laminating the sheet elements into a plurality of laminated pieces and further laminating the laminated pieces together with spacers to form a plurality of laminar blocks which can be assembled into a single structure. 
     The electrode spacing conversion feature can be achieved with each laminated piece regardless of whether it is produced by laminating the sheet elements alone or by laminating the sheet elements together with the spacers to obtain convenient shapes. If a plurality of laminar blocks produced by laminating a plurality of laminated pieces together with the spacers are assembled to form a large-sized boxlike shape, for example, it is possible gather the bottom electrodes arranged at small intervals in a central area of a bottom surface of the electrode spacing conversion adaptor and distribute the top electrodes arranged at large intervals in a broader top surface area of the electrode spacing conversion adaptor. 
     In another aspect of the invention, the electrodes arrayed at greater intervals may be clustered to form a specified number of electrode groups. 
     In this construction, the electrodes distributed in the individual electrode groups can be arrayed such that the electrode groups correspond to the individual matrix circuit devices without providing an additional fixture between the electrode spacing conversion adaptor and the matrix circuit devices. 
     In a further aspect of the invention, an insulating sheet may placed on one side of each sheet element to cover one side of the conductors which are exposed on both sides of each sheet element. The conductors and the remaining part of each sheet element may be made of an electrically conductive rubber material and an electrically nonconductive rubber material, respectively. 
     In this construction, conductors exposed on one side of the each successive sheet element can be insulated and, therefore, it is not necessary to apply a dielectric coating on each sheet element before laminating the sheet elements. 
     These and other objects, features and advantages of the invention will become more apparent upon reading the following detailed description in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a exploded perspective diagram showing the general construction of an electrode spacing conversion adaptor according to an embodiment of the invention; 
     FIG. 2 is an enlarged exploded perspective diagram showing the construction of a laminar block; 
     FIG. 3 is an enlarged fragmentary perspective view of a laminated piece shown in FIG. 2; 
     FIG. 4 is also an enlarged fragmentary perspective view of the laminated piece of FIG. 2; 
     FIG. 5 is an enlarged exploded perspective diagram showing the construction of another laminar block; 
     FIG. 6 is an enlarged fragmentary perspective view of a laminated piece shown in FIG. 5; 
     FIG. 7 is also an enlarged fragmentary perspective view of the laminated piece of FIG. 5; 
     FIG. 8 is an explanatory diagram showing a method of producing a sheet element shown in FIG. 2; 
     FIGS. 9A-9C are also explanatory diagrams showing the method of producing the sheet element of FIG. 2, in which FIGS. 9A and 9B are enlarged fragmentary cross-sectional diagrams taken along lines X—X of FIG. 8; 
     FIGS. 10A-10B are schematic views of the electrode spacing conversion adaptor of the embodiment; and 
     FIG. 11 is a diagram showing how the electrode spacing conversion adaptor of the embodiment is used for testing a printed wiring board. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Specific embodiments of the invention are now described, by way of example, with reference to the accompanying drawings. 
     Each of the laminar blocks  10  includes a plurality of laminated pieces  10   a  and spacers  15   a ,  15   b ,  15   c  which are assembled into a shape suited for assembly with the laminar blocks  20  to form the single structure. As shown in FIG. 2, each laminated piece  10   a  is made by laminating a plurality of sheet elements  11 , each of which is formed into a steplike angled shape suited for lamination. 
     Referring to FIGS. 3 and 4, each sheet element  11  has top and bottom electrodes P, Q and parallel conductors  12   a , and insulating sheets  13  are placed between the successive sheet elements  11 . Each sheet element  11  includes a lower vertical portion  11   a  carrying the bottom electrodes P, an upper vertical portion  11   b  carrying the top electrodes Q, and a horizontal portion  11   c  connecting the lower vertical portion  11   a  and the upper vertical portion  11   b , the bottom electrodes P being electrically connected to their corresponding top electrodes Q via the individual conductors  12   a . The conductors  12   a  including the electrodes P, Q are made of an electrically conductive rubber material and the remaining part of each sheet element  11  is made of an electrically nonconductive rubber material. 
     The lower vertical portion  11   a  and the horizontal portion  11   c  of each sheet element  11  have a thickness t 1  and the upper vertical portion  11   b  has a thickness t 2  which is larger than the thickness t 1  (t 2 &gt;t 1 ). The conductors  12   a  including the bottom electrodes P have a width W 1  and are arranged with a conductor-to-conductor spacing W 3  in the lower vertical portion  11   a  of each sheet element  11 , while the conductors  12   a  including the top electrodes Q have a width W 2  and are arranged with the same conductor-to-conductor spacing W 3  in the horizontal portion  11   c  and the upper vertical portion  11   b  of each sheet element  11 , wherein the width W 2  is made larger than the width W 1  (W 2 &gt;W 1 ). From this, it is understood that the bottom electrodes P are arranged at intervals of d 1 a=W 1 +W 3  and the top electrodes Q are arranged at intervals of d 2 a=W 2 +W 3 , where d 2 a&gt;d 1 a. In this construction, the top electrodes Q are clustered to form a specified number of electrode groups A as illustrated in FIG.  4 . Each insulating sheet  13  has a thickness t 3  and covers one side of the individual conductors  12   a  which are exposed on both sides of each successive sheet element  11 . 
     Each laminated piece  10   a  is formed by laminating the sheet elements  11  in such a way that their lower vertical portions  11   a  are stacked at intervals of d 1 b=t 1 +t 3  and their upper vertical portions  11   b  are stacked at intervals of d 2 b=t 2 +t 3 , where d 2 b&gt;d 1 b. In each laminated piece  10   a  thus constructed, the bottom electrodes P are arranged at intervals of d 1 a and d 1 b in two horizontal directions which are perpendicular to each other, while the top electrodes Q are arranged at intervals of d 2 a(&gt;d 1 a) and d 2 b(&gt;d 1 b) in the two horizontal directions to form the multiple electrode groups A as stated above. 
     The laminated pieces  10   a  are stacked with the spacers  15   c  placed between the successive upper vertical portions  11   b  which carry the top electrodes Q, and each laminar block  10  is completed by attaching the spacers  15   a  and  15   b  on the outside and the inside, respectively, as shown in FIGS. 1 and 2. In each laminar block  10 , the groups A of the top electrodes Q are arranged in a crosshatch configuration as depicted in FIGS. 2 and 4. 
     Referring now to FIGS. 1 and 5, each of the laminar blocks  20  includes a plurality of laminated pieces  20   a  and spacers  25   a ,  25   b ,  25   c  which are assembled into a single structure. As shown in FIGS. 5-7, each laminated piece  20   a  is made by laminating a plurality of sheet elements  21 , each of which is formed into an L-shape in top view that is suited for lamination. Each sheet element  21  includes a first vertical portion  21   a  carrying bottom electrodes P which have the same thickness t 1  as the lower vertical portion  11   a  of the sheet element  11  and a second vertical portion  21   b  carrying top electrodes Q which have the same thickness t 2  as the upper vertical portion  11   b  of the sheet element  11 , where (t 2 &gt;t 1 ). The sheet elements  21  are made of the same materials as the sheet elements  11 , and the bottom electrodes P are connected to their corresponding top electrodes Q via the individual conductors  22   a.    
     Like the conductors  12   a  of the sheet elements  11 , the conductors  22   a  including the bottom electrodes P have the width W 1  and are arranged with the conductor-to-conductor spacing W 3  in the first vertical portion  21   a  of each sheet element  21 , while the conductors  22   a  including the top electrodes Q have the width W 2  and are arranged with the conductor-to-conductor spacing W 3  in the second vertical portion  21   b  of each sheet element  21 , where W 2 &gt;W 1 . From this, it is understood that the bottom electrodes P are arranged at intervals of d 1 a=W 1 +W 3  and the top electrodes Q are arranged at intervals of d 2 a=W 2 +W 3 , where d 2 a&gt;d 1 a. In this construction, the top electrodes Q are clustered to form a specified number of electrode groups A as illustrated in FIG.  7 . An insulating sheet  23  having the thickness t 3  is placed on one side of each successive sheet element  21 . 
     Each laminated piece  20   a  is formed by laminating the sheet elements  21  in such a way that their first vertical portions  21   a  are stacked at intervals of d 1 b=t 1 +t 3  and their second vertical portions  21   b  are stacked at intervals of d 2 b=t 2 +t 3 , where d 2 b&gt;d 1 b. In each laminated piece  20   a , the bottom electrodes P are arranged at intervals of d 1 a and d 1 b in two horizontal directions which are perpendicular to each other, while the top electrodes Q are arranged at intervals of d 2 a(&gt;d 1 a) and d 2 b(&gt;d 1 b) in the two horizontal directions to form the multiple electrode groups A as stated above. 
     The laminated pieces  20   a  are stacked with the spacers  25   c  placed between the successive second vertical portions  21   b  which carry the top electrodes Q, and each laminar block  10  is completed by attaching the spacers  25   a  and  25   b  on the outside and the inside, respectively, as shown in FIGS. 1 and 5. In each laminar block  20 , the groups A of the top electrodes Q are arranged in a crosshatch configuration as depicted in FIGS. 5 and 7. 
     The individual sheet elements  11  are produced by using mold blocks  51 ,  52  and mold plates  53   a ,  53   b ,  54   a ,  54   b  which are illustrated in FIGS.  8  and  9 A- 9 C, in which FIGS. 9A and 9B are enlarged fragmentary cross-sectional diagrams taken along lines X—X of FIG.  8 . 
     Referring to FIG. 8, an array of grooves  51   a  corresponding to the conductors  12   a  in the upper vertical portion  11   b  of each sheet element  11  are formed in a front surface of the mold block  51 . There are formed steplike raised stages  51   b ,  51   c  which are used for positioning on both sides of the array of the grooves  51   a . On the other hand, an array of grooves  52   a  corresponding to the conductors  12   a  in the horizontal portion  11   c  and the lower vertical portion  11   a  of each sheet element  11  are formed in top and front surfaces of the mold block  52 , respectively, and raised stages  52   b ,  52   c  to be used for positioning are formed on both sides of the array of the grooves  52   a . When placed on the top surface of the mold block  52 , the mold block  51  can be moved forward or backward for exact propositioning. The mold plate  53   a  is shaped to fit properly between the raised stages  51   c  on the front surface of the mold block  51  and between the raised stages  52   c  on the top surface of the mold block  52 , whereas the mold plate  54   a  is shaped to fit properly between the raised stages  53   c  on the front surface of the mold block  52 . Similarly, the mold plate  53   b  is shaped to fit properly between the raised stages  51   b  on the front surface of the mold block  51  and between the raised stages  52   b  on the top surface of the mold block  52 , whereas the mold plate  54   b  is shaped to fit properly between the raised stages  52   b  on the front surface of the mold block  52 . 
     The sheet elements  11  are produced by the following procedure. First, the mold block  51  is set at a specified position on the mold block  52  and the mold plates  53   a ,  54   a  are fitted to the mold blocks  51 ,  52 . The electrically conductive rubber material is poured in a molten form into empty spaces between the mold blocks  51 ,  52  and the mold plates  53   a ,  54   a  to form the conductors  12   a  as shown in FIG.  9 A. Next, the mold plates  53   a ,  54   a  are replaced with the mold plates  53   b ,  54   b  and the electrically nonconductive rubber material is poured in a molten form into an empty space between the mold blocks  51 ,  52  and the mold plates  53   b ,  54   b  to form the insulating sheet  13  as shown in FIG.  9 B. Subsequently, an intermediate product including the insulating sheet  13  and the conductors  12   a  is placed in unillustrated male and female molds and the electrically nonconductive rubber material is poured in a molten form into empty spaces between the male and female molds to complete a sheet element  11  shown in FIG.  9 C. Since the mold block  51  can be moved forward or backward along the top surface of the mold block  52 , it is possible to form the horizontal portion  11   c  of the sheet element  11  to a desired length. The sheet elements  21  can be produced using the same technique as described above with reference to the sheet elements  11 . 
     As already stated, the laminar blocks  10 ,  20  produced in the aforementioned fashion are joined together to form the electrode spacing conversion adaptor shown in FIGS.  1  and  10 A- 10 B. In the electrode spacing conversion adaptor thus constructed, all of the bottom electrodes P are gathered in a central area B of a bottom surface of the electrode spacing conversion adaptor as shown in FIG. 10B, while the top electrodes Q are divided into the multiple electrode groups A as shown in FIG.  10 A. 
     Referring now to FIG. 11, the electrode spacing conversion adaptor of the embodiment is used for automatic testing of a printed wiring board Pba in combination with a test unit  30 . 
     The test unit  30  includes a baseboard (substrate)  31  on which a plurality of matrix circuit devices  32  are arranged to the match the individual top electrodes Q of the electrode spacing conversion adaptor. Unillustrated contact terminals are formed on the bottom of the individual matrix circuit devices  32  to make electrical connections between the matrix circuit devices  32  and the corresponding top electrodes Q in the relevant electrode groups A of the electrode spacing conversion adaptor. To exchange input and output signals, the matrix circuit devices  32  are connected to an unillustrated external control circuit via flexible flat cables C which are attached to the baseboard  31 . 
     The contact terminals of the individual matrix circuit devices  32  can be automatically connected to all the corresponding top electrodes Q of the electrode spacing conversion adaptor by placing the test unit  30  in close contact with a top surface of the electrode spacing conversion adaptor. With this arrangement, signals from a pair of top electrodes Q to which a pair of contact terminals that belong to one or two matrix circuit devices  32  are connected can be selectively led to the external control circuit based on address signals fed from the external control circuit via the flat cables C. All the bottom electrodes P in the central area B of the bottom surface of the electrode spacing conversion adaptor can be connected to test points on a conductor side of the printed wiring board Pba by placing the electrode spacing conversion adaptor on the printed wiring board Pba so that the printed wiring board Pba comes into close contact with the central area B. 
     The test unit  30  sequentially selects a pair of top electrodes Q of the electrode spacing conversion adaptor via a pair of contact terminals that belong to one or two matrix circuit devices  32  based on the address signals fed from the external control circuit, and signals from desired two test points on the conductor side of the printed wiring board Pba are led to the external control circuit via the bottom electrodes P corresponding to the selected top electrodes Q. Consequently, the external control circuit can judge whether conductor pattern of the printed wiring board Pba is satisfactory or faulty by measuring the resistance across the selected top electrodes Q. This is because a judgment on compliance or non-compliance to requirements of the conductor pattern of the printed wiring board Pba can be made based on a collection of data on electric conduction between specified pairs of two tests points. 
     According to the invention, the laminar blocks  10 ,  20  need not necessarily have the above-described angled shapes but may be formed into simple boxlike shapes. Such boxlike laminar blocks may joined to together form an electrode spacing conversion adaptor or used singly as one-block electrode spacing conversion adaptors. In another variation of the invention, the conductors  12   a ,  22   a  may be formed by printing an electrically conductive paint on a surface of each sheet element  11 ,  21  or by using generally known conductor pattern forming techniques used in producing printed wiring boards. The laminar blocks  10 ,  20  are not limited in their structure to the illustrated examples but may be formed by combining any desired numbers of laminated pieces  10   a ,  20   a.