Dear Paul&Jason (sounds like a rock group),
your openminded support and will to do something is something. Now,
gage vs. syringe will be under observance, so will your experience about
hardrunning still without heat build-up. The one who told about it: did
you guess or did you in fact measure the tip's heat? Don't grasp what
you mean with 'simple' men, suspect some sort of double-edge paraphrase.
Your thumb rule 8xflaw size is good. Our auger has a trapetsoid thread,
outer circumference polished, space in between very rough indeed, you
say this roughness doesn't matter, thought opposite. Mentioned silver
filled polymer not same problems as with lead/tin ditos, then what's the
difference: (corn) flakes vs. balls? Are balls less benign to clogging
than flakes?
See you on the CRT glass
Ingemar Hernefjord
Ericsson Microwave Systems
> Jason,
> once you'll go over 24 gauge (25, 26) ; you'll need 400-500 mesh ;
> we use indium nc-smq90 in 200 gms cartridges ; on 644 head ;
> 2x 200 on back (2x 50 on front) .
> eventually (after a year we found the mesh price difference did
justify the
> yields ; about 1-2 blocked needles a week with nonstop three shifts)
we
> dropped the 325 all together ;
> dispensing 400-500 only across all gauges .
> The pressure running up to auger is 25 psi (on 200 cartridge); 10 (on
50
> cartridge).
> We run second year on it ; it's proven , no problems ; ask indium guys
for
> 200gr ResMed's package and give it a shot (you need to make yourself
custom
> clamp ; to counter the G's generated)
>
> And > Inge did cry about silver loaded polymer, not solder/flux paste:
not
> quite the same .
>
> Scott,
> never experienced the increased temps even after 8 hour literally non
stop ;
> on Gemini's validations all went in (paste, silver, glue, thermal
transfer
> compounds) ;
> and the needle never touches the board (the foot does) .
>
> Tim decided to stay incognito ; which is a pity ; not what the net is
about
> .
>
> So finally , dear nett(?)er Inge :
> When you look onto those suspended silver particles under your trusted
scope
> ;
> you find that those ain't particularly balls (camelot says for example
the
> inner needle dia should be minimum of 8x the ball [solder]size)
> I particularly do not think you need a rocket; morphology; fluid
dyno's;
> rheologies and polishing compounds and tolerancing sciences to give
you a
> hint you're applying wrong needle gauge for the job . The auger's side
walls
> (twiddling in ceramic shaft I presume) are precision ground ; the
inner of
> needles is good enough .
> By the sound of it you just started this applications ; therefore you
have
> in front of you a lot of trials and validations, and the simple men
from
> manufacturer (not paste supplier) would do you good as they did
(should) a
> lot of it .
>
> Being simple man myself ; I'd (perhaps naively) presume to push down
up to
> 50(!)um silver boulders through 100(!)um inner orifice may cause you a
> mighty pain :
> this being caused by sheer wishful thinking .
>
> Familiar indeed
>
> Anyhow, wish you luck ; keep in touch if you're still stuck ;
> and let me know what you thought (don't hold back ; I can take it)
about my
> reflection on the thermal transfer = how did your bubbles go ???
> Werner said he prefers steaks to snitzels ; and I have to admit I
always saw
> the breadcrumbs "extension" as poor culinary pretences .
> Sorry Norman , done now
>
>
> Paul Klasek
> http://www.resmed.com
>
>
>
>
>
>
>
>
>
>
>
>
>
> -----Original Message-----
> From: jason gregory [mailto:[log in to unmask]]
> Sent: Saturday, 14 August 1999 0:20
> To: [log in to unmask]
> Subject: Re: [TN] clogging dispensers
>
>
> I had the same problem and addressed it on the smtnet.com site. I was
using
> a paste mesh that is suitable for screening, not dispensing (325/500
mesh).
> I figured the only bad thing that would occur would be that the paste
> wouldn't flow as easily through my nozzle. After purging the pump to
remove
> all air bubbles, the flow would stop and I would disassemble the pump
and
> find a hard, shiny chunk of solder at the end of the pump, before the
> nozzle, impeding the flow, that appeared reflowed. My guess, coupled
with
> knowledgeable persons agreeing, was that the mesh indicates a larger
ball
> size and the "resistance" of the balls to flow through the nozzle was
> causing great friction inside the pump, compounding the balls together
and
> possibly the constant friction was causing the backing-up solder to,
in
> essence, "flow". Check your paste mesh. BTW, I am using a Camalot 5000
with
> an Archimedes-style pump. Hope some of this helps.
>
> > -----Original Message-----
> > From: [log in to unmask]
> > [SMTP:[log in to unmask]]
> > Sent: Friday, August 13, 1999 8:41 AM
> > To: [log in to unmask]
> > Subject: [TN] clogging dispensers
> >
> > Out of 1,700 netters, someone should have an idea about this:
> >
> > We need expertise advice immediately to solve a mystery with
clogging
> > high speed automatic dispensers. Three silver epoxy pastes give same
> > clogging. Fresh pastes are bought. Same. Dispenser screws, tubes,
pumps,
> > all details are cleaned thoroughly. Same. New dispenser parts
installed.
> > Same. Whatever we do. Same. After running some minutes-hours:
clogging
> > in the needle. Some say that the room humidity must be very exact in
> > order to make the dispenser epedize well. Others talk about local
curing
> > inside the paste. And some think sedimentation can be the plague.
> > Experts from the paste manufacturer will be here in one or two days,
but
> > according to my experience, they seldom have that kind of knowhow,
> > machine makers can have, this one not. Most oftenly, the knowhowers
are
> > people like you, dear nett(l)ers.
> >
> > I have my own theory, but can't prove it yet. Namely, that this
> > "conglomerate" or mix of fluids and silver flaws (1-50um) can be
> > PRESSURE DEPENDENT, i.e. at certain constant or momentary pressure,
> > there will be a separation in the narrowest part, the needle, fluids
> > will drop out and separate, leaving the coarser silver flaws without
> > fluency, they will clog. Also, I have seen that the inside of the
needle
> > (inner dia 100um) is not polished, but has a rather grainy stucture,
> > likwise the rotating helix that feeds paste. Both should be
polished, I
> > suppose. There is a science that use morphology and fluiding
dynamics
> > that possibly can give a clue, but I'm rather far from that art,
maybe
> > some of you have education of the sort.
> >
> > Familiar to someone?
> >
> > Remo@Alenia, if you read this, please contact me, I have lost your
> > adress.
> >
> > Thanks in advance/
> > Ingemar Hernefjord
> > Ericsson Microwaves Systems
> >
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