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Method for solder mask crack termination grooves for a folded package

IP.com Disclosure Number: IPCOM000033181D
Publication Date: 2004-Nov-30
Document File: 4 page(s) / 61K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for solder mask crack termination grooves for a folded package. Benefits include improved functionality and improved performance.

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Method for solder mask crack termination grooves for a folded package

Disclosed is a method for solder mask crack termination grooves for a folded package. Benefits include improved functionality and improved performance.

Background

      A crack can be stopped if stress relieving holes are applied at the ends of the crack line. The holes relieve the stress in the material.

      Cracks propagate at the edges of a brittle solder mask material applied over a substrate when the substrate is folded. The folded region is a highly stressed area. The cracking can lead to the breaking of the electrical connections in the substrate and device failure (see Figure 1 and 2).

The solder mask cracks can be initiated by the saw singulation processes.  The cracks are further propagated by the folding process and other handling and thermal stresses, particularly at the fold region.

      Conventionally, the cracking problem is solved by using a lower-productivity saw singulation process with a slower feed rate. Cracking is reduced but not completely eliminated. Another method is to completely remove the solder mask from the fold region, which can lead to undesirable shorting between traces due to contamination, leading to the deterioration of the signal/circuit quality (see Figure 3).

Description

      The disclosed method uses grooves on a solder mask at the highly stressed fold region of a folded package to terminate the propagation of solder mask cracks.

              The key elements of the method include (see Figure 4):

•             Solder mask placed at the sides of the folding region to ease saw singulation

•             Crack termination grooves on the solder mask placed on the sides of t...