Re: [CAD_CAM_EDM_DRO] Re: Cleaning Circuit Boards

The biggest problem with imbedding bits in a PCB I've found is the small
pulse transformers often used in some servo controller designs. If you get
small bits of metal dust lodged in the transformer winding it can shift the
characteristics of the transformer enough for the high-side of the bridge to
malfunction.

Blow drying shouldn't be a problem though, 40-50psi from a filtered supply,
someone mentioned putting a shop rag over the nozzle?

I've cleaned numerous boards from computer gear, power supplies and one or
two servo amps using phosphate free detergent and warm water then air dried.
The only casualties I've had are a couple of pulse transformers, old mylar
caps which fell apart and one SMD IC that blew off the PCB when drying never
to be seen again... I think it's in orbit now :-).

I've also used "multi" which is a spray-and-wipe type household cleaner with
good success then rinsed under a tap and air dried.

I have never used high-pressure air mind you, only ever 40-50 PSI, accept
for that one SMD incident, which I think was 120psi. A lot of workshop air
nozzles are set at 80-120PSI which is good for blowing chips off a machine
or blow drying solid metal parts. Not so good for a delicate PCB assembly.

Cheers, Chris.

* Design engineer, Assembly worker, Cleaner.
* Ohmark Electronics. PO Box 5302, Christchurch, New Zealand.
* http://www.ohmark.co.nz

----- Original Message -----
From: Smoke <Smoke@...>
To: <CAD_CAM_EDM_DRO@egroups.com>
Sent: Monday, November 27, 2000 8:06 AM
Subject: Re: [CAD_CAM_EDM_DRO] Re: Cleaning Circuit Boards


> I'd recommend vacuumn instead of blast. Way back in '75 when I was
working
> with electronics, I learned....and "relearned" it again recently in
computer
> school...that using an air blast can imbed minute particles in the circuit
> board(s), possibly causing all kinds of problems that you'd never be able
to
> find.
>
> with the advent of today micro electronics, I'd suspect the problem would
be
> even worse now.