Pan Pacific Symposium Conference Proceedings


Author: Steve Sytsma & Dan Lynch
Company: Hamilton Sundstrand
Date Published: 2/25/2005   Conference: Pan Pacific Symposium

Abstract: Chip-on-Board (COB) manufacturing using the combination of Die Bonding and Wire Bonding has been a common process in the thick film hybrid industry for 30+ years for a wide variety of applications, with the most common being electronics for Automotive, electronic watches, calculators, large capacity portable memory devices, satellites and limited military applications.

The space and cost savings of going to bare die is well documented in the industry. In an effort to reduce cost, reduce weight and increase performance, efforts are being made to replace the standard thick film alumina substrate with low cost, high temperature organic substrates for COB applications. There are three key challenges in transitioning to COB: process integration for power electronics applications, thermal management, and long-term product reliability validation.

The core manufacturing technologies necessary to successfully implement an integrated COB/SMT capability include utilization of a rigorous RFP process and full understanding of the key SMT and hybrid assembly manufacturing equipment, assembly materials and processes. Mechanical and thermal-mechanical considerations for high power, high heat generating applications common in Automotive and Aerospace products and require creative use of existing thermal and mechanical simulation and testing tools to predict Mechanical integrity and Functional reliability.

Unique failure modes based on the use of epoxy die attach, lead-bearing solder, and lead-free solders in combination with naked die and low-cost organic substrates are driven by a wide variety of process and material factors. Comprehensive understanding of common defects and defect mechanisms for die attachment materials and the rework & repair trade-offs associated with each material can go a long way to facilitating material selection, process deployment, mechanical integrity and functional reliability.

Key words: Hybrid, Chip on Board, COB, Reliability.

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