Building on our 25 years of proprietary and patented innovation for the global electronics packaging industry, Air Products has developed a novel flux-free soldering technology that uses activated hydrogen at ambient pressure with a starting temperature as low as 100° C to remove metal oxides from electroplated solder bumps on semiconductor wafers and permit reflow of these bumps to obtain the proper shape and size for interconnection onto a package or substrate.
Left: As Received: SEM micrograph of electroplated solder bump
Right: EA-DD: SEM micrograph of solder bumps reflowed by
applying the EA process
The electron attachment (EA) technology for hydrogen activation is a novel flux-free technology, which can be operated at ambient pressure and normal solder reflow temperatures using non-flammable mixtures of hydrogen (<4 vol%) in nitrogen. This technology, invented by Air Products, involves generating a large quantity of low-energy electrons. Some of the electrons attach to hydrogen molecules, forming active species for effective oxide removal.
Air Products has partnered with Sikama International to introduce an electron attachment fluxless reflow system (EAUP1200) to the electronics wafer level packaging segment. The furnace is designed to remove metal oxides from solder bumps on UBM wafers and solder caps from copper pillar wafers via the EA technology. The activated hydrogen produces hydrogen anions, which induces reflow of the solder to a final shape in the absence of traditional flux processes.
Air Products-Sikama EA Technology Furnace
Fluxless soldering using Electron Attachment (EA) technology overview
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Fluxless Soldering in Activated Hydrogen Atmosphere
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Production-Scale Flux-free Bump Reflow Using Electron Attachment
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