SMT RF shield Dewetting & Misalignment

Q1) How to identify on good or bad RF shield that could contribute to dewetting? A1) We use Alloy 770 and 752 [German silver] for our RF shields. We have never seen a solderability issue, even aged stock solders well.

* Nickel Alloy 752, Nickel Silver 65 - 18 [65% Cu / 17% Zn / 18% Ni] * Nickel Alloy 770, Nickel Silver 55 - 18 [55% Cu / 27% Zn / 18% Ni]

Frame considerations: Shield frame design also involves a number of important considerations, including: * Must have pick-up spot for automated installation * Must have termination lip area * Larger the termination footprint, the better the shield * More metal-to-metal contact, the better the shield

Q2) What counter measure that must be taken when facing dewetting issue? A2) Purchase materials that solder well. If you don't do that, screen parts at incoming inspection. If you don't do that, rework parts on the line.

Q3) What counter measure that must be taken when facing misalignment issue after reflow process? (Before reflow oven the alignment is good/center) A3) Properly solderable terminals on the shield float on the melted solder and self-align. When the terminals don't solder well, the poorly soldering terminals create a imbalance in the self-alignment of the terminals and the the shield torques from the desired position.

When using terminals that you know are going to cause misalignment problems, you might consider gluing them in-place with chip bonder.

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