About this document
Attempts to replace silver with copper in power semiconductor die attach go back a long way. What has blocked the switch is a copper oxide film a few nanometres thick. This technical note sets out an approach that addresses that barrier with a PDA functional layer combining reduction and oxidation resistance in a single surface layer, together with the supporting evidence.
Download
An English edition is not available yet. The Korean document is below.
Summary
Silver is not one layer of bonding material; it creates an entire process system. Silver paste brings double-sided silver plating with it, so this is not only a raw material cost question. Switching from Ag to Cu lowers cost and raises bond reliability, but the thin oxide film on the copper surface has stood in the way. Instead of making the reducing agent stronger, Cools integrated the reduction function into the same surface layer that provides oxidation resistance. The PDA functional layer performs dispersion, oxidation resistance and interfacial reduction at once, and works so that pressure selects where bonding happens and heat selects when. Particles and electrodes bond by the same principle, so double-sided silver plating is unnecessary. Eighteen appendix items carry the mechanism, the calculations and the PoC test design.
Conclusion
Oxide removal through to Cu neck formation proceeds as one continuous event, and the growing Cu neck pushes the PDA and organic residues out of the conduction path. Silver paste and double-sided silver plating disappear together. The transition does not call for a new plant. It removes the Ag-dependent steps from an existing sintering line, and first commercialization begins by changing a single component, the Cu particle, in an existing Cu paste. Application starts in power semiconductors and extends to thermal die attach for high-power logic chips under high-temperature, high-current and large-area conditions. The appendix defines the first PoC test design, the required analyses, and the observable signals that should appear if the mechanism holds. The method is to state in advance what must be visible if the hypothesis is true.
Topics
- Power semiconductors
- Bonding materials
