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Browse Prior Art Database

Method for a BGA package with improved coplanarity

IP.com Disclosure Number: IPCOM000032216D
Publication Date: 2004-Oct-26
Document File: 3 page(s) / 70K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a BGA package with improved coplanarity. Benefits include improved yield and improved throughput.

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Method for a BGA package with improved coplanarity

Disclosed is a method for a BGA package with improved coplanarity. Benefits include improved yield and improved throughput.

Background

      Yield loss occurs when poor solder ball coplanarity causes product to not meet the required specification. Conventionally, this problem is solved by controlling the substrate package land coplanarity. Techniques include substrate core materials management, mechanical/thermal stress consideration, and tighter land coplanarity specifications.

      Poor coplanarity is typically the result of warpage caused by mechanical or thermal stress during processing.

      Ball coplanarity control is increasingly critical for larger ball grid array (BGA) packages. Coplanarity is determined by the original substrate land coplanarity and process-related parameters (substrate and package processes) before the ball coplanarity test. Because many parameters interact, optimizing and improving each parameter is difficult.

      Because the coplanarity fallout rate is not negligible and the fallout is at the last package assembly test, the yield loss directly results in the unacceptable revenue loss.

      After attaching a die on a substrate, the same size of solder balls (lead/tin eutectic or lead-free composite) are mounted on the land side (the opposite side of a die side) of the substrate. Ball coplanarity is tested for every unit and only the passed units are shipped to customers, who mount chips on the mother boards and reflow them. If the coplanarity is not controlled, customers typically observe open failures due to a gap between the solder paste and BGA balls (see Figure 1).

      Every BGA pa...