Soldering method
First Claim
1. A soldering method for direct attachment of electronic chips to a flexible circuitized substrate comprising the steps of:
- providing a first solid solder on contacts of said chips;
providing a second solder in which said first solder is miscible on contact pads on said flexible substrate;
placing said chips at corresponding pads on said flexible circuitized substrate;
heating where said first and second solders interface for effecting eutectic bonding therebetween.
1 Assignment
0 Petitions
Accused Products
Abstract
A method is described for attaching circuit chips to a flexible substrate (laminate) using controlled chip collapse connection technology (C-4). The substrate is "tinned" with an alloy of eutectic composition in its contact region with the solder balls on the base of the chip. The alloy and the solder are chosen such that they are miscible. The system temperature is raised above the alloy melting point thus causing the alloy and the solder to mix, the mixture composition moving away from the eutectic composition with time and thus raising its melting point. Eventually the mixture melting point is higher than the temperature at which the system is maintained and the mixture solidifies to form a contact. In this way contact between the chip and the flexible substrate can be effected at a temperature below the melting point of the pure solder and lower than one which would result in degradation of the laminate adhesive.
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Citations
11 Claims
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1. A soldering method for direct attachment of electronic chips to a flexible circuitized substrate comprising the steps of:
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providing a first solid solder on contacts of said chips; providing a second solder in which said first solder is miscible on contact pads on said flexible substrate; placing said chips at corresponding pads on said flexible circuitized substrate; heating where said first and second solders interface for effecting eutectic bonding therebetween. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 11)
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9. A soldering method for direct attachment of electronic chips to a flexible, circuitized laminated substrate comprising the steps of:
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coating contacts on said chips with a tin-lead solder, with tin comprising about 3-10% thereof; covering contact pads on said substrate with 63% tin, 37% lead solder; placing said chips on said substrate so as to align chip contacts and corresponding contact pads on said substrate; and heating said solder covering said contact pads to a temperature for reflowing said solder, while applying uniform pressure, and effecting a eutectic bond between said chip and said substrate. - View Dependent Claims (10)
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Specification