Improving the reliability of radar T/R module with precise cleaning technology
Because we adopt high precision microelectronic assembly technologies during the manufacturing of radar T/R modules, these modules are complex and delicate. Common cleaning technologies such as ultrasonic cleaning can't satisfy the requirement of high precision cleaning of these modules. This article introduces some precise cleaning technologies, these cleaning technologies not only can make T/R module achieve a high cleanness, but also does little harm to them, and they will greatly improve the reliability of T/R module.
A new bumping process using lead-free solder paste
In this paper, we report development of a new process for lead-free solder bumping with no flux residues, using stencil printing and hydrogen radicals, which can lessen both the environmental load and the manufacturing cost of solder bumping. In this process the reduction of the hydrogen radicals, instead of the flux, will eliminate the surface oxides of the stencil printed lead-free solder paste. Sn-3.0Ag-0.5Cu lead-free solder paste, which contains no residue flux was printed on an 8-in wafer. Hydrogen plasma was radiated for a minute during the reflow process, and the printed paste formed a bump. Reflow experiments without hydrogen radicals treatment were also carried out for comparison, where no successful reflow could be observed.
Oxidation and reduction kinetics of eutectic SnPb, InSn and AuSn: a knowledge base for fluxless solder bonding applications
For microelectronics and especially for upcoming new packaging technologies in micromechanics and photonics, fluxless, reliable and economic soldering technologies are needed. In this article we consequently focus on the oxidation and reduction kinetics of three commonly used eutectic solder alloys: SnPb, InSn and AuSn. The studies of the oxidation kinetics show that the growth of the native oxide, which covers the solder surfaces from the start of all soldering operations is self-limiting. The rate of oxidation on the molten, metallic solder surfaces is significantly reduced with decreasing O/sub 2/ partial-pressure. Using in-situ Auger Electron Spectroscopy (AES) it could be shown for the first time, that H/sub 2/ can reduce Sn-oxide as well as In-oxide at moderate heating durations and temperatures. In the second part of this study the results, obtained by the investigation of oxidation and reduction kinetics, are applied to flip-chip (FC) bonding experiments in vacuum with and without the injection of H/sub 2/. Wetting in vacuum is excellent but the self-alignment during flip-chip soldering is restricted. The desired, perfectly self-aligned FC-bonds have been only achieved, using evaporated and reflowed AuSn(80/20) and SnPb(60/40) after the introduction of H/sub 2/.