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.
Fluxless solder bumping in flip chip package by plasma reflow
A new fluxless reflow process using Ar+10%H/sub 2/ plasma was investigated for application to solder bump flip chip packaging. The 100 /spl mu/m-diameter Sn-3.5wt%Ag solder balls were bonded to 250 /spl mu/m pitch Cu/Ni under bump metallurgy (UBM) pattern by laser solder ball bumping method. Then, the Sn-Ag solder balls were reflowed in Ar+H/sub 2/ plasma. Without flux, the wetting between solder and UBM occurred in Ar+H/sub 2/ plasma. During plasma reflow, the solder bump reshaped and the crater on the top of bump disappeared. The bump shear strength increased as the Ni/sub 3/Sn/sub 4/ intermetallic compounds formed on initial reflow stage but began to degrease as coarse (Cu,Ni)/sub 6/Sn/sub 5/ grew at solder/UBM interface. As the plasma reflow time increased, the fracture within solder bulk decreased and the fracture along solder/UBM interface increased. The off-centered bumps self-aligned to UBM pattern during plasma reflow. The solder ball defect occurred in high power and a long time plasma reflow.