Ingemar,
Just kind of curious as to how your diving friends might make or answer that
call!
Blub...glub lol...and it's not quite Friday yet
Regards,
Colin McVean
Circuit Manufacture Ltd
Unit 9-12
Rowleys Green Lane
Longford
Coventry
CV6 6AG
Tel: 02476 666168
Fax: 02476 637089
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Ingemar Hernefjord
(KC/EMW)
Sent: 18 November 2004 09:41
To: [log in to unmask]
Subject: Re: [TN] Alternatives to Conformal Coating?
John,
We studied some units from the car industry. Cheap but efficient way of
making tough electronics.
Seems as your product fits into your category. I would buy thinwall
stainless steel open boxes,
bring that card in and pot with silicon and use a silicon rubber protected
cable to communicate with the
outside. Omit the thought of connectors. The power transistors can be
mounted directly to steel box.
And mount them with open side down. I have a friend who designs the
electronics for handheld motorsaws,
his units can be drowned in petrol, water, oil..anything. Same idea as I
mentioned above.
Simple and cheap..no? Then I have the cheapest of all, used by diving
friends: http://phoneus.ronniebou.net/phone/waterproofelectroniccase.html
Ingemar Hernefjord
Ericsson Microwave Systems
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of John Parsons
Sent: den 17 november 2004 20:08
To: [log in to unmask]
Subject: [TN] Alternatives to Conformal Coating?
Greetings all,
We are a fab shop and are looking for a solution to a problem being
experienced by one of our customers. They have a board which resides in a
somewhat hostile environment
- steam/salt water vapour
- board carries 20Amp current
- susceptible to multiple thermal excursions which put further
stress on
the unit
The problem, as one might expect, is that the soldermask is not man enough
for the job. Some units have exhibited significant solder mask flaking from
the conductors after as little as 4 hours of operation. FYI, board is
double sided with 3oz base Cu.
The product is currently only in the prototype stage but production volumes
are expected to be in the 100,000-250,000 units annually. We have proposed
the obvious solution of utilizing a conformal coating post assy but that is
an option they would initially prefer to avoid due to the inherent costs
involved. They would like us to first exhaust any possibility that the
problem can be averted from the pcb fabrication level. I should also
mention that the expected lifespan of the unit is a maximum of 1000hrs and
likely only several hundred hours.
Some options that have been discussed are; (in no particular order of
likelihood to succeed of fail!)
- multiple coating of soldermask
- micro etch of copper prior to mask application (currently pumice
scrub)
- conductor pacification with oxide alternative. If this does not
provide
additional bite for the mask it may provide additional protection from
corrosion once the mask has pealed off.
Any ideas from the lot of you? Are there properties to specialty solder
masks which might be beneficial in this application? Any options to
conformal coating??
Regards
John Parsons
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