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Method of Package Saw Partial Cut on QFN

IP.com Disclosure Number: IPCOM000235655D
Publication Date: 2014-Mar-18
Document File: 2 page(s) / 141K

Publishing Venue

The IP.com Prior Art Database

Abstract

With the industry trend moving towards reducing the test costs in final manufacturing, strip testing offers the most savings for small QFN devices. Before testing, the devices must be isolated, yet remain physically attached to the strip. Use of a first partial cut as an isolation poses challenges in the subsequent testing process due to strip warpage. This paper describes a method to perform the first partial cut with reduced chance of warpage.

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Method of Package Saw Partial Cut on QFN

Abstract

With the industry trend moving towards reducing the test costs in final manufacturing, strip testing offers the most savings for small QFN devices. Before testing, the devices must be isolated, yet remain physically attached to the strip.  Use of a first partial cut as an isolation poses challenges in the subsequent testing process due to strip warpage.  This paper describes a method to perform the first partial cut with reduced chance of warpage.

Introduction

Strip test offers an opportunity to reduce test costs significantly. However, it requires the strip to have minimum warpage post first partial cut in order to ensure it is indexed and aligned with the array of test contacts during testing. Any strip warpage may cause high yield loss at test due to contact issues and offset/incomplete cut at second full cut due to misalignment of lead frame fiducial.  In this paper we present a method to perform the partial cut by dispensing an epoxy gel along the first partial cut saw street prior to the second full cut to address the warpage concern.

Design and Implementation

Figure 1 shows the process flow for the proposed method. We perform the first cut using a thinner blade and then fill the partial cut saw street with epoxy gel.  Epoxy cure is optional and depends on the material selection.  The second cut (full cut) after testing is done using a thicker blade to ensure all of the epoxy gel is removed after device singulation...