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Subject:	Degolding helicopters
From:	"Ingemar Hernefjord (KC/EMW)" <[log in to unmask]>
Reply To:	TechNet E-Mail Forum <[log in to unmask]>, Ingemar Hernefjord (KC/EMW)
Date:	Tue, 25 Jan 2005 11:38:12 +0100
Content-Type:	text/plain
Parts/Attachments:	text/plain (25 lines)

Hi. We call them so. Helicopters. Microwave SOTs with four wings. For teflon boards with hardback. Now, we've found that they are oftenly real gems, with up to 10 microns of gold from toe to knee. If they aren't degolded, you'll get IMCs en masse after soldering. The exteriour of such joints is well known: matte, greyish, prismatic, full of needles and plates. I've etched the surface of a typical one to demonstrate the joints interiour, see Steve's gallery.

MIL and SPACE have stringent requirements for soldering goldplated terminals, e.g. this typical one:

http://xweb.nrl.navy.mil/glast/CALDesign/CDE/CAL%20DPD%20Wire%20Cable%20Soldering%20and%20Staking%20Spec%20Rev%202.doc

Now to the practice. How on earth do you degold the legs on components that are not much bigger than what a fly leaves on your breakfast plate? Solder pot? Solder iron? Njet possible. Instead, we use to handsolder with a somewhat exaggerated amount of solder, then heat each leg separately and suck the solder with a Pace or similar, and then resolder with fresh solder. Thus, we get rid of most of the gold-contaminated solder.

A'm curious about other's tricks. Anyone take the bate? Mr Creswick...ah..knew he couldn't resist...

Ingemar Hernefjord
Ericsson Microwave Systems

PS. Many SOT makers do not specify what gold thickness they have. Will be surprise...

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