Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
2000-10-16
2002-04-30
Paladini, Albert W. (Department: 2841)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C174S259000, C029S832000, C257S737000
Reexamination Certificate
active
06380492
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a contact film used for devices having a ball grid array structure which uses solder balls as external terminals and to a mounting structure for such devices, and particularly to a contact film and a device mounting structure wherewith verification of the electrical contact with the solder balls constituting the external terminals can be easily made, and wherewith more stable contacts are provided.
2. Description of the Related Art
There is an increasingly strong demand for super-miniaturization in semiconductor devices built into such very small and lightweight information instruments as portable terminals, portable telephones, and digital cameras. In response to such demand, semiconductor devices having a ball grid array (BGA) structure, wherein solder balls are deployed in a lattice configuration as the external terminals of the package, are being widely used. Large LSIs such as microprocessors and ASICs require a very large number of input/output terminals, and the BGA package structure is becoming indispensable in order to make that necessity compatible with the demands for super-miniaturization.
With such BGA type devices, how to perform accelerated tests and performance tests is a very important issue. With a BGA type device which uses solder balls as the external terminals, in tests prior to shipment, it is not possible to melt (reflow) the solder balls and effect mounting on a test board. It is the device customer who ultimately melts the solder balls and effects mounting by mounting on a print board, and what is demanded of the device manufacturers is that they perform accelerated tests and performance tests, effecting mounting on a test board without causing a deterioration in the shape and so forth of the solder balls.
Of the test sockets for BGA type devices conventionally proposed, such as in Japanese Patent Application Laid-Open No. H8-37255, for example, the structure thereof is such that openings are provided in the socket electrodes, the BGA solder balls are caused to make contact such that they are accommodated in those openings, and a socket cover is pressed down from above. This test socket only succeeds in improving the sureness of the electrical contacts, and cannot actually verify the electrical contacts.
Also proposed, in Japanese Patent Application Laid-Open No. H11-26128, is a contact film wherewith, in order both to make electrical contact with external terminals possible and to eliminate damage to the solder balls, a conductive connection pad and conducting pattern are formed between flexible multi-layer insulating layers, the connection pad is exposed through a window formed in the outermost insulating layer, and the solder balls of the device are pressed against the connection pad to make contact therewith. However, although it is possible, by employing flexible multi-layer insulating layers, to prevent damage to the solder balls in the testing process, and to more surely effect contact even with solder balls exhibiting variation in diameter, it is not possible with the contact film proposed here to verify the electrical contact with the solder balls.
In yet another proposal, in Japanese Patent Application No. H-10-365591 filed (on Dec. 22, 1998) by this patent applicant, a new test socket is proposed wherewith attaching a contact film that contacts a BGA type device is made possible, and the use of a common test socket for various models of BGA device is made possible. Nevertheless, even this contact film cannot verify electrical contact with the solder balls.
SUMMARY OF THE INVENTION
That being so, an object of the present invention is to provide a contact film for use with BGA type devices, and a mounting structure using that contact film, wherewith electrical contact with the solder balls can be verified.
Another object of the present invention is to provide a contact film for use with BGA type devices, and a mounting structure using that contact film, wherewith electrical contact with the solder balls can be stabilized.
Yet another object of the present invention is to provide a contact film for use with BGA type devices, and a mounting structure using that contact film, wherewith electrical contact with the solder balls is effected without damaging them.
In order to attain the objects stated above, a first aspect of the present invention is a contact film for making electrical contact with a ball grid array device in which a plurality of solder balls is deployed in a lattice configuration as external terminals, comprising: a first elastic insulating film having multiple contact openings provided at positions corresponding to the solder balls, and first contact patterns for making first contact with the solder balls about the peripheries of the openings; and a second elastic insulating film, laminated to the first elastic insulating film, having second contact patterns for making second contact with the solder balls through the openings at positions corresponding to the openings; wherein it is possible to verify the electrical contact of the solder balls by whether or not there is electrical continuity between the first and the second contact patterns.
According to the invention described above, the diameter of the openings provided in the first flexible insulating film is smaller than the diameter of the solder balls, but those holes are formed in such size as that the bottommost points of the solder balls just make contact with the second contact pattern. Then, by providing the first contact patterns at the peripheries of the openings and mounting such that the solder balls are pressed thereagainst, the solder balls can contact the first contact patterns more surely without being damaged. Furthermore, because the second contact patterns with which the bottommost points of the solder balls make contact are deployed below the openings, it is easy to verify whether or not the solder balls are in contact with the first contact patterns by verifying the electrical contact between the first and the second contact patterns.
In a preferable embodiment of the present invention, the first flexible insulating film has a multi-layer structure. Also, the first flexible insulating film is configured in N layers for a BGA device having N rows of solder balls. In the case where N=3, for example, first contact patterns and contact openings for the outermost row of solder balls are formed in a first layer film. The first layer film has through holes for respectively passing the solder balls from the second row in.
First contact patterns and contact openings for the second row of solder balls are formed in a second layer film laminated to the first layer film. In the second layer film are provided, furthermore, lower-layer openings at positions corresponding to the outermost row of solder balls and lower-layer contact pads about the peripheries thereof, and through holes for respectively passing the solder balls from the third row in. The first contact patterns of the first layer film and the lower-layer contact pads of the second layer film are in mutual contact, and the one or the other makes contact with the outermost row of solder balls.
First contact patterns and contact openings for the third row of solder balls are formed in a third layer film. In the third layer film are provided, furthermore, lower-layer openings at positions corresponding to the outermost row and the second row of solder balls and lower-layer contact pads about the peripheries thereof. The first contact patterns of the first layer film and the lower-layer contact pads of the second and third layer films are in mutual contact, and one or other thereof makes contact with the outermost row of solder balls. Also, the first contact patterns of the second layer film and the lower-level contact pads of the third layer film are in mutual contact, and the one or the other makes contact with the second row of solder balls.
In cases where the BGA has four or more rows of solder balls, first contact pattern
Armstrong Westerman & Hattori, LLP
Fujitsu Limited
Paladini Albert W.
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