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Subject: Re: 0.5mm pitch breakout board?

From: "Andrew" <andrewm1973@...>
Date: 2007-08-18

> Leon wrote:
> I've done one or two single-sided QFN boards for
> accelerometers, I find it best to make one at a
> time.

Leon,

How do you hold your boards one at a time ?

I just use the clips that came with the etch tank
(Which BTW are over twice the size of the PCB).
If I try use them with a board that is too small
and can float around they end up one side up and
one down in the bubble flow and one side gets
over etched.

I use 4 sided leadless packages all the time for
the AVR CPUs and normally dont have an issue
because they normally have a 0.5mm lead pitch.
With the 0.5mm lead pitch I can use 8-10 thou
tracks.

The one I am using for a current project is a
QFN28-4 that has a 0.45mm lead pitch. I have
droped down to 6-8 thou tracks which seems to
be my etching limit with CuCl.