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Post-Reflow Plating of Solder Bumps for Repair and for Redundant Conductor Disclosure Number: IPCOM000181688D
Original Publication Date: 2009-Apr-09
Included in the Prior Art Database: 2009-Apr-09
Document File: 2 page(s) / 34K

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Solder bumps are used to join chip-to-package or chip-to-chip attachment. However, there are a number of problems with solder bump yield and reliability, especially at small dimensions: (1). cracking or dewetting of solder during die attach and (2) electromigration of solder. Hence, what is described in this article is a process and structure for improved solder ball yield and reliability.

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Post-Reflow Plating of Solder Bumps for Repair and for Redundant Conductor

The proposed process uses plating (either electroless or electroplating) after solder ball reflow to repair defective solder balls and adds a redundant conductor for improved electromigration reliability.

The process flow is as follows:
a. Join chip to package using conventional solder reflow
b. Repair damaged solder balls using electroless plating or electroplating of solder or Cu
c. Use channels to aid flow of plating solution
d. Remove disposable metal from backside of package using wet etch, dry etch, or grinding.

Fig. 1. Chip joined to package. Additional plating is performed after chip join to improve reliability. Channels are provided for enhanced flow of plating bath between chip and package. A disposable metal film is provided on backside of package as an electrode during electroplating.

Channels for plating bath

            Disposable Metal plate for electroplating (optional) Fig. 2. Repair C4 that cracks during chip join.

Bond pad


Before repair





Chip 2 package

Bond pad


Additional solder by electroless or electroplatiing

Fig. 3. Provide redundant conductor C4 solder ball to improve electromigration lifetime.

after repair


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Bond pad


Bond pad Additional solder by electroless

or electroplatiing
Redundant conductor for longer EM lifetime; Cu, Ni, or Cu/NI
Cu = 0.1-0.5 um, Ni = 1.0-20 um


Before plating

after repair