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Compliant Pad for Solder Attached BGA Devices

IP.com Disclosure Number: IPCOM000249315D
Publication Date: 2017-Feb-16
Document File: 3 page(s) / 182K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method to reduce stress on solder balls in attached Ball Grid Array (BGA) devices. The novel solution utilizes a uniquely designed compliant or flexible pad, to which a solder ball attaches, that allows the board and device to expand and contract.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 52% of the total text.

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Compliant Pad for Solder Attached BGA Devices

Currently, many Ball Grid Array (BGA) attached modules are highly sensitive to mismatches in the coefficient of thermal expansion (CTE) between the board and the module. This causes hot tears and fatigue cracking of solder balls during manufacturing, power cycling, and rework operations. Fluctuations and uneven heating of the component and board results in stress being driven into the solder ball. Failures (e.g., cracking, tears, etc.) can occur either in the solder ball itself, or at the solder ball/solder pad interface. This results in constant or intermittent signal failures.

The novel solution utilizes a uniquely designed compliant or flexible pad to which a solder ball attaches. The compliant pad can exist on either the BGA device and/or the Printed Circuit Board (PCB). This compliant pad allows the board and device to expand and contract during thermal cycling, without putting additional stress on the solder ball. This pad element can be produced utilizing Trace/Via Hybrid (TVH) technology.

Compliant Pad Structure A pad with some flexibility to accommodate CTE mismatch extends off the BGA package or PCB to which a solder ball is attached. The flexible/compliant pad could be formed in a curved shape, z-shape, spring coil, helix, or other geometry that would give the same benefit. Two potential compliant pad structures are shown in Figure 1.

Figure 1: Potential compliant pad structures 1. Illustration of chip package with curved compliant pads with solder balls attached

2. Illustration of chip package with z-shaped compliant pads with solder balls attached

Description of Compliant Pad Manufacturing This disclosure leverages the TVH process to fabricate a compliant pad (such as those shown in Figure 1). The pad is continuous with the internal package copper traces or vias and extends past the top of the package for the solder balls to attach. This can be accomplished in two approaches:

· The entire BGA package or PCB is produced using the TVH technology ·...