i'd be inclined to talk to the faa and boeing about this since a 747 blew up over the atlantic because of a electical failure in the fuel tank. i mean PLEASE talk to the faa and boeing.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Diamond, Pat
Sent: Wednesday, December 08, 2004 5:04 AM
To: [log in to unmask]
Subject: [TN] Poor solder cup plating
Hi Technetters,
we have a potential problem, after our connector manufacturer went out of
business, we tried an alternative approved company who manufactured some
evaluation samples.
The samples we received showed evidence of missing/contaminated plating in
the bottom of the solder cups. After soldering and cross sectioning some of
the cups, there was evidence of non-wetting and flux entrapment in the
bottom of the cup. When we contacted our supplier, they stated that due to
the configuration constraints and the plating method, they cannot guarantee
to produce 100% plated parts every time (we have also had this confirmed by
alternative sources).
We have devised an alternative manufacturing method which will correct the
problem but will not receive part for approximately 3 months!
Some background information on the product:
The unit the connectors are used on, is an aircraft fuel density sensor
which sits in the fuel tank and measures the amount of fuel on board say a
747.
After assembly, the connectors are potted with an epoxy and then electron
beam welded to the sensor which has been previously evacuated to 3 E-4 Mbar.
My question is; given that the solder has wetted fully on the outside (and
most of the inside) of the cup and that the connectors are in a vacuum, will
the flux entrapment cause corrosion etc. with the passage of time?
A few bits of further info:
* The cup is made from 1.02mm Diameter Nilo 50 and the plating is 2.5
microns of electro-tin, flow brightened over a copper undercoat
* The solder used is HMP- 93.5%Pb/5% Sn/1.5%Ag
* The flux used is Ersin 362 Rosin activated
* The operating temperature spec is -55 +125 degrees C
The other unfortunate problem is that we cannot change the cup material or
the plating method!
Any help/advice you can offer would be appreciated.
Pat Diamond
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Pat Diamond
Senior manufacturing Engineer
Weston Aerospace Tel: +44 (0)1252 868122
124 Victoria Road Fax: +44 (0)1252 370298
Farnborough, Hampshire, GU14 7PW Web www.westonaero.com>
England Email mailto:[log in to unmask]
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