Cracked a solder joint troubleshooting a radar unit in Tucson

Last Tuesday I was chasing intermittent azimuth errors on a Hawk radar dish and finally saw a cold solder joint crack under thermal cycling, right where the coax meets the IF board. I've done hundreds of these repairs but this one took 4 hours because the crack only showed under a magnifying glass. Has anyone else seen these joints fail after the lead-free transition, or is it just this older unit?

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rowank8321d ago

...and that's exactly why I'm not surprised you had to bust out the magnifying glass. I was reading a tech bulletin from the Navy a while back about lead-free solder cracking in high vibration and thermal swing gear, and they found most failures happen right at the component leads where the stress concentrates. The crack can be hairline thin, almost invisible until you hit it with bright light and a loupe. Your Hawk unit might be older but the solder might've been reworked at some point with the newer stuff, that mixes real bad. I've seen it on avionics where a repair from 2005 with leaded solder gets touched up later with no-lead and it just starts micro-cracking after a few hundred cycles. Sounds like you did the right thing by checking the coax to IF board junction first, that's a classic spot for it.