SMTA China Conference Proceedings

The Special Hot Bar Soldering with Copper Balls Process Development for Mixed Signal Module Application

Authors: Louis Lv, Isaias Daguio, Jumbo Huang, Henley Zhou, RSivam VRajoo, Engsiang Khor, JoJo Vigo, Dragon Chin, and Murad Kurwa
Company: Flextronics
Date Published: 4/22/2014   Conference: SMTA China

Abstract: This paper is in English and Chinese languages.

Mixed Signal Module (MSM) is special application which requires a complicated manufacturing process such as Underfill, Three Layer POP Assembly, Cleaning and Hot Bar soldering. The low stand-off attributes of the three layers Package on Package (POP) brought challenges to underfill and cleaning processes. As an integral part of the MSM manufacturing assembly, hot bar soldering of FPC into the ceramic substrate material contributed a lot of challenges to the process and material selection.

Hot bar soldering challenges are primarily due to the low stand-off height, avoid secondary reflow for POP, susceptibility of ceramic crack, and stringent cleanliness requirement.

In this paper, we introduced the special hot bar soldering with copper balls process development for Mix Signal Module application, attaching the Flexible Printed Circuit (FPC) to the ceramic board. A low temperature lead free solder paste mixed with copper balls were carefully selected through a various evaluations in order to meet the customer's requirement. Process optimization and validation were run through a tremendous Design of Experiments (DOE). Furthermore, hot bar soldering comparative study of the laboratory results between with copper balls and without copper balls will be also discussed in this paper.

Key Words: 

Copper Ball, MSM, Hot Bar, FPC, Ceramic Board, DOE, Low Temperature Lead Free Solder Paste, Peel Strength, Cross Section, Scanning Electron Microscope (SEM) and Intermetallic Compound (IMC)

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