Electronics Assembly Knowledge, Vision & Wisdom
High Reliability, Stress-free Copper Deposit
High Reliability, Stress-free Copper Deposit
To overcome the challenge of metallizing smooth surfaces, a new stress-free electroless copper was developed to serve this important sector.
Materials Tech

Materials Tech programs cover topics including:
Adhesives, Chemicals, Cleaning Solutions, Coatings, Components, Design, Embedded Technology, Fasteners, Finishes, Flex Circuits, Flip Chip, Fluxes, PC Fab, Solders, Solder Masks, Solder Paste and more.
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Authored By:
Jason Carver
Alvin Kucera
OM Group Electronic Chemicals Maple Plain, MN

Summary
Today's wide variety of laminate materials and specialized dielectric choices pose a challenge for process engineering. In particular, smooth surfaces, such as polyimide, flex circuit substrates and rigid-flex constructions with window cut-outs, can be a challenge for electroless copper and plating processes. Conventional electroless copper systems often required pre-treatments with hazardous chemicals or have a small process window to achieve a uniform coverage without blistering. To overcome the challenge of metallizing smooth surfaces, a new stress-free electroless copper was developed to serve this important sector of the printed circuit industry.

Conclusions
Select additives can be added to an electroless copper solution which decrease the stress of an electroless copper deposit. The reduced stress allows for a blister free copper deposit on smooth, difficult to metallize substrates such as PI. These additives showed no adverse effects on the interconnect reliability of the resulting copper deposit when exposed to thermal stress as evaluated by solder shock and IST.

Initially Published in the IPC Proceedings

Comments
Can you supply continuous resistance measurement of daisy chains using an actual assembly reflow profile instead of a simulated reflow thermal stress that does not match a real cycle? Also, please provide the cross-section view of the daisy chain stitch. Was the chain powered directly or indirectly. Following simulated reflow, claim is chains passed around 1000 cycles. How many coupon were produced and were there any as fabricated failure?
Jerry Magera, Motorola Solutions
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