Browse Prior Art Database

Diagonal Strain Wall

IP.com Disclosure Number: IPCOM000146368D
Publication Date: 2007-Feb-13
Document File: 2 page(s) / 428K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that uses 90° trapezoidal solder joints at the four corners of the ball grid array (BGA); the stronger solder joints act as a "wall" to handle more board flexure forces. Benefits include reducing mechanical stress failures and saving PCBA scrap costs.

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Diagonal Strain Wall

Disclosed is a method that uses 90° trapezoidal solder joints at the four corners of the ball grid array (BGA); the stronger solder joints act as a “wall” to handle more board flexure forces. Benefits include reducing mechanical stress failures and saving PCBA scrap costs.

Background

Currently, mechanical stresses cause “open solders” on the BGA solder joints. This failure occurs when there are solder cracks in the solder joints or the pad crater. Collected board flexure data from the eutectic process shows that mechanical stress failures can easily happen to lead-free products. The lead-free strain limit is ~≤300 - 500ue; however, data collected from the eutectic processes (especially the ICT and System Assembly) show board flexures of more than
 ≥ 600ue. Currently, the only control for board flexure is to have the manufacturing process tuned to achieve a board flexure less than the specified limits. However, this adds costs to the fixture (ICT, FT, manual and mechanical, and system assembly) and reduces process flexibility.

General Description

The disclosed method creates stronger corner solder joints that withstand more stresses in the diagonal direction of the component. Pressure on the current design corner solder joint (see Figure 1) is

Po

= (F1 / Lo); pressure on the disclosed method corner solder jo...