Hi hetal,

Maybe they should be asking why they are potting at all? (maybe a conformal
coating with parylene?)

Honestly from your mail the design team seem to be disconnected with
reality.

Used to be that they would take the RF properties of their proposed design
into account and arrange materials/ RF power output (for
transmission)/front end amplification (for receivers) into account.

The absolute last thing they should be doing is asking an assembly house to
specify a potting material in an RF design and then ask the vendor of the
material if it is going to be an issue.....

Suggest that the assembly house might want to push back on this and ask what
exactly the attenuation limits of the materials should be in order for the
design to pass DVT/PVT testing.

On the mechanical issue I have seen assemblies use a 2 part potting process,
the first as a semi-compliant coating, the second as an epoxy coating over
the top of the first.

I am sure others here on TechNet will be able to help on the mechanical
questions.

On the RF performance the designer will need data sheets on the materials
and a mechanical estimation of the depth of potting materials over the
board/transmission component surfaces - he will need data on dielectric
constant of the materials - and to be honest to avoid problems of the
assembly house facing "failed on test yield" issues I would recommend a full
pilot run with DVT and PVT testing on the pilot units. Unless they have a
master plan for re-working potted assemblies?...............8-)

Best regards,

John Burke

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Hetal Shah
Sent: Thursday, August 12, 2010 10:08 AM
To: [log in to unmask]
Subject: [TN] Is Calcined alumina in Epoxy resist tramission signal..?

Our customer  have an RF Transmitter on the PCB. they have a couple of
concerns.
 One that the potting material will damage the components and the other that
the potting material will shield the RF Transmissions of their transmitter.

Their assembly house was going to use our 2 parts Epoxy (which conatains
Calcined alumina) as the potting material.  Will this create any of the
problems mentioned?


Any insight into this matter would greatly be appreciated.



Thank you

Hetal Shah

R & D Chemist

MG Chemicals


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