Metal working – Method of mechanical manufacture – Assembling or joining
Patent
1984-12-03
1986-02-04
Hearn, Brian E.
Metal working
Method of mechanical manufacture
Assembling or joining
29589, 29847, 357 80, H01L 2160, H01L 2158, H05K 332, H05K 1304
Patent
active
045676437
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method of replacing an electronic component connected to conducting tracks of a supporting substrate and is applicable more specifically to components of the chip type mounted on circuits manufactured by hybrid technology.
In this technology, electronic components are applied to a supporting substrate which is covered in conducting tracks and connections are made between the connection points of the components and the conducting tracks by means of wires made, for example, of gold or aluminium, which are welded by thermo-compression or by means of ultrasound.
The replacement of a component by another on a substrate is an operation which may be necessary for different reasons, the most common of which is the repair of a circuit which is faulty due to bad functioning of a component.
In view of the small size of the components and of the conducting tracks which serve them, the replacement of a component by another is an operation which is very difficult to perform, in particular because it usually requires the faulty component to be disconnected and removed from the substrate.
It is necessary to remove the connecting wires from the faulty component at substrate level without damaging the substrate and without breaking the wires into several pieces, the wires being in general less than 100 microns and more specifically 25 microns in diameter so that microscopic pieces thereof would create short-circuits in other points of the circuit. Moreover the conductive tracks should not be damaged because this could either interrupt electrical continuity or else prevent adherence of the repair connections.
Removing a faulty component is equally very difficult. The polymerized glue which is generally used yields with difficulty. When trying to remove the component, the substrate may be ruptured making any repair impossible, or the component may break, leaving pieces still adhering which have to be eliminated one by one; in any case, even if the glue yields easily, the state of the surface to be used for re-glueing is of poor quality. As regards the possibility of heating the defective component, although this is very efficient, it causes thermal stress and risks of loosening of nearby components, thus weakening the circuit in an unacceptable manner.
A method which is sometimes used consists in leaving the defective component in place and applying a new component thereon, after removing the initial connections one by one.
Up to now, this method could only be used if the component had a small number of interconnecting wires (not more than about 10, for example) because otherwise the risk would be too great and the time for carrying out the operation too lengthy for this method to be worth using. This method is in any case not practicable when the body of the component, as is the case in many instances, must be connected to a potential by means of a bonding area because in this case there would be no more contact between the back face of the component with the bonding area.
The present invention thus proposes a method of replacing an electronic component which is electrically connected to conducting tracks of a substrate by means of conducting wires, which method overcomes the above-listed drawbacks.
According to a characteristic of the invention the method of replacing the component comprises the following steps: be taken out of service, the zones where the connecting wires are attached to the tracks, service, service, the cuts.
The characteristics and advantages of the invention will be more accurately shown in the course of the following description with reference to the figures given herein below.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 represents an example of a conventional mounting of an electronic component on a substrate;
FIG. 2 represents an example of a mounting obtained after using the method in accordance with the present invention;
FIG. 3 represents a substrate whose conductive strips have been modified in order to permit performance of the method in accordance with the pre
REFERENCES:
patent: 3969813 (1976-07-01), Minetti et al.
patent: 4012832 (1977-05-01), Crane
Anderson et al. "Josephson Package Repair", IBM Tech. Disc. Bull., vol. 26, No. 12, May 1984, pp. 6244-6245.
Patent Abstracts of Japan, vol. 5, No. 167, p. E-79-839 Published Oct. 24, 1981.
IBM Technical Disclosure Bulletin, vol. 24, No. 12, May 1982, p. 6371, M. L. Buller et al., "Back-To-Back Chip Pack".
Droguet Jean-Paul
Teissier Gerard
Vernay Michel
Hearn Brian E.
Hey David A.
Sintra-Alcatel
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