Steve ; Andy ; this is interesting ( am I glad we don't print paste !) :
Do you (and Andy and Matt ) actually say you need different apertures for
different fluxes (within realistically similar viscosities ; releasability ;
etc.) ?
And the 50% volume flux ; would there be means of playing with paste
composition contents to be able use the
400 at $ 400 ; uhhhh ; that IS A heavy pill to swallow with a painful GRIN
upon hitting the budget bottom !
I believe Steve it made the beancounters do unmentionables .
Andy ; I know Steve will absolutely deny there is any other way to no bath,
bull, and balls due to pending liability for $ 160 gran !!! ( no wonder he
choked on calculations ! ) ;
but ; just between us & The Forum (ex the legend ) ; would there be a no
paste composition allowing same paste stencil ?
This ball business is really so severe out there ?
If you'll keep solidarity cover just in case Steve's ex boss with big memory
watches the Net ; I understand .
The test strips are indeed good and seems versatile as well :
on SIR ; as you said on solderability ; we have a repeatability shear pads
on them as well (interpolated to reliability test) .
On your note " bridged wide gaps are good guys" : one of the cutest things
on the Ind. NC paste is it's wickability :
you can smear continuous line over the QFP and in reflow it all wicks in to
individual pads evenly :
What I'm trying to say : I understand you test the adhesion ; but on the
balance you may toss something very good out with something very bad .
Hey Andy ; lettin' you know what I think just because you asked for it .
Be gentle on me with the lead ball sizing ; I just find it hard to believe
you have to chuck the car if you can change the seats to fit in ?
Thanks ahead for the insights
See you folks
Paul Klasek
http://www.resmed.com
> ----------
> From: Stephen R. Gregory[SMTP:[log in to unmask]]
> Sent: Friday, 29 January 1999 4:14
> To: [log in to unmask]
> Subject: Re: [TN] Design considerations for No-Clean processes
>
> In a message dated 1/27/99 8:41:13 PM Pacific Standard Time,
> [log in to unmask]
> writes:
>
> > Here is one for the Design and Assembly folks.
> > We are a high volume OEM of consumer electronics.
> > My Assembly has converted to a No-Clean process.
> > What are the differences that I should be concerned with at the design
> > level?
> > Should I have concerns about or modify any designs left over from the
> > Aqueous days?
> > Thanks for the help
>
> > FNK
> >
> >
> > Frank N Kimmey, C.I.D.
> > EM Designer
> > C & K Systems, Inc.
> > 916-353-5366
> > [log in to unmask]
>
> Hi Frank!
>
> I was with a memory company when we converted from water soluble to
> no-
> clean, and there were a few suprises for the finance department that
> weren't
> realized when the decision was initially made to change processes.
>
> One of he biggest expenses was stencils. We had over 400 different
> part
> numbers of SIMM's, DIMM's, Cache Modules, & PCMCIA products...you wouldn't
> believe the number of stencils we had. Well, they were all made when we
> washed
> everything. Stencil apertures for all passive components were 1 to 1
> except
> for the industry standard etch factor compensation...and most of you can
> guess
> what happened when we used those stencils with no clean. You got it!
> Squeeze
> ball city! Not a big deal when the boards get a bath before they leave the
> factory, because they normally always wash off...(that's why everybody
> lives
> with this process defect in a cleaning environment) but a very big deal
> when
> you're no-clean. Every last one of the stencils needed to be
> replaced...and at
> a average of $400 a pop at 400 stencils...(that's ummmm...lessee,...zero
> times
> zero equals zero, and then 4 times...oops wait, gotta take off my shoes
> now..)....uhhhh...just TRUST ME, it's a whole lotta moola! (GRIN)
>
> Another thing that drove the costs up was the fact that we couldn't
> buy
> material the way we had in the past. Couldn't give those 100,000 board
> orders
> to fab vendors anymore to keep the prices down, and let the PCB's languish
> around on the stockroom shelves oxidizing and expect to solder em' with
> no-
> clean. Same thing went for the DRAM. Used to buy from anybody and
> everybody,
> but had to be a little more selective when the process changed.
>
> One thing you might do in your designs, if you haven't already, is to
> implement some sort of SIR comb pattern that you put on every one of your
> designs. It's up to you where you want it to be. It could be one like
> what's
> on IPC's B-24 board or as simple as two unmasked traces next to each
> other.
> What we were doing since practically every one of the products we build
> was
> panelized, we put them on the coupons, or skirts of the panel. They went
> along
> in the process just like the SIMM's did so we would test them. That way
> when
> we wanted to to a SIR test we wouldn't tie up any shipable product.
>
> Another thing that I think that's pretty important, is to standardize
> on
> a surface finish and mask type that you use on all your fabs. We used o
> get
> boards from about 5 or 6 main vendors, and to try and get your arms around
> all
> of them so they're all giving you the same thing can be a bear, but it
> really
> makes things easier and more predictable on the production floor.
>
> Good Luck!
>
> -Steve Gregory-
>
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