[NLRS] Re: LFCSP (was re:power measurement)

[Chris Elmquist]

On Monday (02/13/2006 at 03:43PM -0600), Dr. Gerald N. Johnson wrote:
> Worth looking at some more. I don't find solder paste in Mouser or
> Allied. Haven't checked Digi-key, they won't let me have a full catalog
> and the little is too skinny to bother opening. Dial up slows their web
> page searches. In Mouser there are several hot air soldering stations
> starting at about $500 with several K as the limit, along side Weller
> Soldering Guns that should have never been made.

Digikey has a few options:

http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?Ref=164517&Row=437421&Site=US

$42 for 35G Syringe

SMT rework stations can be found on eBay in the $1xx price range.  Eg,

http://cgi.ebay.com/NEW-SMT-SMD-HOT-AIR-SOLDER-DESOLDER-REWORK-STATION-8205_W0QQitemZ7589114484QQcategoryZ36327QQrdZ1QQcmdZViewItem

although I don't know anything about the quality of such a unit having
never used one.

> The storage life of solder paste is short because of oxidation of the
> fine solder particles in the flux. But I bet stuff that didn't meet NASA
> requirements would still make ham gear.
> 
> Solder masks should be a help, but a lot of tiny work depends on surface
> tension of the molten solder to break or prevent solder bridges. And
> with the small area of the boards, and the relatively low cost of the
> tiny chips, scraping is probably cheaper than trying to do any rework in
> the factory.

I would think the main goal is to save the board and the rest of the
parts on it.  My experience with rework though was always in prototype
and engineering lab situations and so the capability was still important
there.  Production was seldom reworked as you point out.

I don't have much experience making boards either--  and I am not talking
about etching them but rather the layout.  I have sat down countless times
with CAD tools and only become frusterated at the lack of symbols and the
time required to generate them that I have always scuttled the project.
I need to get past this first...  Too many years of being spoiled by
someone else doing layout for me I guess.

Chris N0JCF

-- 
Chris Elmquist
mailto:chrise at pobox.com
http://www.pobox.com/~chrise