Hi Mark,
This is a tough question to answer. The emittance depends on a number
of factors. The oxide treatment used on the inner layers, the reflectivity ogf
the soldermask, whether there is a ground plane near the surface, etc. We have
boards with ground planes near the surface, with a black oxide treatment as an
adhesion treatment and no soldermask. I would guess that this approaches a
"Black Body" emissivitty or about 0.9 emissivitty, however this is a guess. I
don't know how others have shown that FR-4 has an emissivitty of 1 ( which
would be a perfect "Black Body"). I have made emissivitty measurements in the
past, and it requires some pretty sophisticated equipment. I would think that
the glossy nature of the soldermasks, that I have worked with, would cause a
good bit of reflectivity rendering the emissivitty, or emitticance if you will,
closer to the mid range or about 0.5 (again this is merely a guess) I know of
no tables that you could look up to inform you. If there is enough interest, I
can tell You the Procedure to make the measurement and the equipment required,
off line.
I'm sure that this does not answer the question, but I hope it helps.
Regards,
Les Connally
[log in to unmask]
> From: Mark Harrand <[log in to unmask]>, on 7/6/98 5:33 PM:
> Technetters,
>
> I'm working on a project that involves radiant heating of a circuit board.
> I need to know the emmitance value for a standard FR-4 board with solder
> mask.
>
> None of my handbooks gives this value, and several internet searches turned
> up nothing. Can anyone help?
>
>
>
> Mark Harrand
> SRC Computers, Inc.
>
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