On 10 December Bob wrote:
>> Hello tech-netters,
>> Does anyone know of any contract service provider(s) for
>> hydro-squegee processing - a method of solder coating resulting in
>> very thin solder using a high pressure oil spray for "blow-off"?
>> Our previous source has gone away... Vertical or horizontal hasl
>> does not work in our application, even after tweeking....
Bob,
I don't know of a vendor that can do what you're asking, but your
email, and one that was posted yesterday, prompts me to throw out a
question to everyone for discussion if anyone is so inclined...I hope
everyone doesn't mind if I digress a little...
You're asking about a HASL process, and the question from yesterday I
was referring to was asking about exposed copper, which leads me into
some questions about surface finishes and questions about OSP's. I've
been assembling boards with OSP coatings regularly for about 2-years
now. Not every product I've been involved with is using OSP's. Most of
the OSP coated products have been PCMCIA products, but right now I'm
working on a PC motherboard we're building that's OSP coated...BTW,
Entech CU-106 is what I'm most familiar with.
My opinion of OSP's from an assembly point of view, is that I think
they're GREAT! Nice flat pads and no board warpage from the heat of HASL
which makes printing less of a pain, a lead-free PCB fabrication
process, and I've found that during reflow the solder tends stay right
where it's been printed and not bridge as much as a HASL'ed fab does
...one of the PCMCIA products was a MPEG card for laptops that had a
15.7-mil QFP that we had to lay down and we built about 10,000 of them.
The soldering yields were surprisingly good, less than 2% had any
bridges at all! The reason I was surprised was that we were using a
AMISTAR machine...not bad equipment, but not known as one of yer'
high-end machine brands.
Anyways, I just wanted to express my view on OSP's, and ask these
questions;
1. Based on my good experiences with them, why would you want to have
your PCB's HASL'ed?
I'm kinda' familiar why such metals as gold or tin/nickle are used,...
conductivity and/or durability, right? So what I mean by the above
question is why one would choose Tin/Lead or HASL over OSP's.
2. Exposed copper: Fact, or Fiction? Is it a real problem?
I've heard so many conflicting sides to this "pain-in-the-you-know-what"
issue. I've heard that the reason exposed copper is a problem, is it'll
be exposed to the air, and when that happens the copper oxidizes. Yeah
right, like it's gonna' break down the copper into a powder, eat all the
traces up, and cause the board to fail. I've also heard that yes, when
bare copper is exposed to the atmosphere it does oxidize, but after the
surface has been coated with a layer of copper oxides, the rate of
oxidation slows dramatically. That makes sense. Otherwise, how in the
world can a house have functioning copper plumbing in it for 50-years,
or you can go in the midwest and see bare copper telegraph wires on
poles that have been out in the elements for decades? So is it REALLY a
problem?
Now I know soldering to oxidized copper is one thing, but that's a
different story, but how about exposed copper after assembly?
__\/__
. / ^ _ \ .
|\| (o)(o) |/|
#------.OOOo----oo----oOOO.-----#
# Steve Gregory #
# [log in to unmask] #
# #
#________________Oooo.__________#
.oooO ( )
( ) ) /
\ ( (_/
\_)
***************************************************************************
* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
***************************************************************************
* To unsubscribe from this list at any time, send a message to: *
* [log in to unmask] with <subject: unsubscribe> and no text. *
***************************************************************************
* If you are having a problem with the IPC TechNet forum please contact *
* Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] *
***************************************************************************
|
