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Rework of PbFree Interconnect on Organic Substrate

IP.com Disclosure Number: IPCOM000240089D
Publication Date: 2014-Dec-30
Document File: 1 page(s) / 26K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method to create temporary chip-attach solutions that can be reworked. The approach creates a temporary interconnect that does not create white bumps.

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Rework of PbFree Interconnect on Organic Substrate

Multi-chip Modules (MCMs) on organic substrate are a key technology for future Silicon integration on a package. Since all components are exposed as useless at module final test if there is even just one defective component on the module, a rework process for MCMs that are identified as being defective is required.

A solution to this problem is to temporarily attach chips that can be reworked. The approach creates a temporary interconnect that does not create other defects, such as

white bumps.

A temporary interconnect structure including a solder interconnect with a soldering hierarchy may be formed by:

1. create a weak interconnect with a low-temperature solder tip on top of C4, or on substrate pad; and


2. after test, remove the the low temperature solder (e.g., with copper (Cu) block,

wet etch, or other process), then reflow the remaining standard (high temperature) solder at full temperature.

Figure: Novel structure

The innovation with this approach is the removal of the low temperature solder. Solder systems go through extensive and longtime reliability stressing. It is desired to maintain a known and well-defined solder alloy. For that reason, it is preferred to remove the low-temperature solder prior to high-temperature reflow.

As an example, a hot-shear may be performed to remove the known "good" chip from the substrate, perform solder removal of the low temperature solder (e.g. with a Cu block or an etc...