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Browse Prior Art Database

Method for a removable solder preform

IP.com Disclosure Number: IPCOM000011846D
Publication Date: 2003-Mar-19
Document File: 3 page(s) / 56K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a removable solder perform. Benefits include improved reliability.

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Method for a removable solder preform

Disclosed is a method for a removable solder perform. Benefits include improved reliability.

Background

        � � � � � A nonuniform separation distance between two packages and/or substrates to the die results in several problems:

•        � � � � Poor solder joint geometry (see Figure 1)

•        � � � � Process-related solder joint failure

•        � � � � Warpage during reflow

•        � � � � Inconsistant standoff

        � � � � � Conventionally, these problems are addressed through time-consuming process characterization and process control. No solder preform is used.

General description

        � � � � � The disclosed method is a removable solder preform. It ensures the required standoff height and solder-joint geometry during reflow. By using this removable solder joint preform, better solder joint geometries can be created to ensure proper aspect ratio. After reflow, the preform can be removed by heat, water, chemical or mechanical methods.

        � � � � � The key elements of the method include:

•        � � � � Removable preform material

•        � � � � Solid-solder spheres or solder paste

•        � � � � Composite copper core, solder coated spheres

Advantages

        � � � � � The disclosed method provides advantages, including:

•        � � � � Improved reliability due to improved solder joint geometries

Detailed description

        � � � � �         � � � � � The disclosed method is a removable solder preform. A polymeric material is formed with the solder balls incorporated (see Figure 2). An example may be low MW polyethylene/flux composite. During the solder ball reflow, the flux that is incorporated into the polymer matrix will reduce oxides on the ball pad surface. The solder metallurgically bonds with the solder ball pad. The polymer matrix that held the solder balls acts...