I have used a similar idea from PCB-video.  It's called the RAID tool and is
basically a molded plexiglass fixture with prisms forming both sides.  Look
down into one and shine the light down into the other.  It's far from the
ERSA scope but it costs only $35.00.  In regards to Richard's idea, Edmund
also has very small glass prisms with a reflective coating on the
hypotenuse.  Someday in my spare time (HA!) I want to fool with these for a
low budget ERSA scope.
John Thorup

> -----Original Message-----
> From: Richard Tilbrook [SMTP:[log in to unmask]]
> Sent: Monday, June 05, 2000 7:12 AM
> To:   [log in to unmask]
> Subject:      Re: [TN] Other visual tests under a BGA possible?
>
> Well, while we're sharing cunning plans, I'll blurt out mine before I
> apply for the
> patent (only kidding).
>
> This one's labour intensive, and I haven't tried it myself yet, so please
> don't
> send me the Blu Peter award for the worst idea, but . . .
>
> - get a 45 degree front coated mirror, Edmund Scientific do one 5x5mm,
> someone else
> might do one smaller
> - place the mirror close to the BGA / heel joint / whatever
> - apply light from that side
> - look down an inspection microscope (perpendicular to the board) at the
> mirror
> - cross fingers and see if there is any visibility
>
> Obviously if you're going to be spending a lot of time looking under
> things this
> isn't the way to do it, but for occasional looks, seeing whats going on,
> someone
> out there might find this a useful and cheap alternative.
>
> Of course, you have to treat front coated mirrors really nicely too, or
> they just
> become prisms.
>
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