Reliability Issues Caused by Bending HDI Flexible CircuitsAuthors: John Dzarnoski and Kexia Sun
Company: Starkey Laboratories
Date Published: 10/24/2010 Conference: SMTA International
There is little published information regarding bendability of multilayer HDI flexible circuits for medical device applications. This paper will examine bending and folding effects on a Polyimide/Adhesive/Copper/Polyimide/Copper/Adhesive/ Polyimide structural stack-up on test coupons and a HDI flexible circuit intended for production use. A forming tool that controls all aspects of the bend process will be discussed. A variety of factors were investigated including bend angle, thickness of the circuit, bend radius, foil weight, copper materials, construction, and frequency of bending. Circuit electrical resistance, substrate microstructure and crack initiation were monitored and will be examined. Failure mechanisms will be discussed as well as their impact on design.
Folding, Reliability, Bending and Radius
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