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Method for VFM processing for post-mold curing of semiconductor packages

IP.com Disclosure Number: IPCOM000146401D
Publication Date: 2007-Feb-13
Document File: 2 page(s) / 10K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for variable-frequency microwave (VFM) processing for post-mold curing of semiconductor packages. Benefits include improved functionality, improved reliability, improved throughput, and improved cost effectiveness.

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Method for VFM processing for post-mold curing of semiconductor packages

Disclosed is a method for variable-frequency microwave (VFM) processing for post-mold curing of semiconductor packages. Benefits include improved functionality, improved reliability, improved throughput, and improved cost effectiveness.

Background

      Conventionally, post-mold curing is one of the most time consuming steps in the packaging process. The curing is performed in a convection oven and can take more than 4 hours at ~175°C.

      Overmolding is an important step for encapsulating the die and substrate into a robust unit. The molding compound is typically a mixture of epoxy-based organic material filled with ~60‑90 wt% of SiO2 particles. The molding process occurs at a high temperature for just a few minutes when the mold compound is fluidic. However, post-mold curing takes several hours at the same high temperature to crosslink the epoxy and harden the mold compound, which limits module efficiency and throughput.

      Variable-frequency microwave technology sweeps a bandwidth of frequencies rapidly around a center frequency to increase the uniformity of microwave energy. Variable frequency ranges include C-band at ~5.8-7 GHz and X-band at ~7.3-8.7 GHz, compared to fixed-frequency microwaves, such as home-use ovens, at 2.45 GHz. Variable microwaving is a volumetric and selective heating process with nearly 100% energy conversion efficiency. The variable frequency microwaves do not cause arcing due to microwave energy being deflected off metal materials.

General description

      The disclosed method is VFM processing for packaging post-mold curing of semiconductor packages. The method reduces the post-mold cure time in packaging by using a mold compound with homogenously distributed fine carbon black and a variable-frequency microwave oven.

      The disclosed method applies to both high-density interconnect and low-density interconnect packaging post-mold cure processes where epoxy and carbon-black based mold compound is used.

      The key elements of the disclosed method include:

•     Variable frequency microwav...