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Control of Solder Sphere Surface Micro-Roughness to Improve the Ball Attach Process

IP.com Disclosure Number: IPCOM000010735D
Publication Date: 2003-Jan-15
Document File: 2 page(s) / 130K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that uses solder spheres with low surface micro-roughness to minimize missing and double balls during the ball attach process. Benefits include an increase in ball attach yield and a reduction in losses due to rejected units.

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Control of Solder Sphere Surface Micro-Roughness to Improve the Ball Attach Process

Disclosed is a method that uses solder spheres with low surface micro-roughness to minimize missing and double balls during the ball attach process. Benefits include an increase in ball attach yield and a reduction in losses due to rejected units.

Background

Currently, the method for checking the sphere surface condition during the ball attach process is using SEM (Scanning Electron Microscope); however, SEM is not able to distinguish differences in surface micro-roughness. Typical SEM photos do not show any difference in surface morphology.

General Description

The disclosed method uses solder spheres with low surface micro-roughness to minimize missing and double balls during the ball attach process. Solder spheres with a higher micro-rough surface will have more interaction with the ball bin surface. These spheres with a rougher surface move less fluidly in the ball bin. Problems, such as missing and double balls, arise as a result of more surface interaction between rough balls and the stencil surface of the ball bin.

AFM (Atomic Force Microscopy) is used to determine micro-roughness of the spheres’ surface. Spheres that have missing or double ball issues are those showing higher micro roughness (see Figure 1).

Advantages

In the disclosed method, missing and double ball issues are anticipated and fixes are put in place before the factory launches into a HVM (High Volume Manufacturing) ru...