Ingemar,
We attempted to attach a thermal couple to the tip and then hook the thermal
couple up to a data logger so we could plot the temperature over time.
Unfortunately the thermal couple wouldn't stay attached to the tip of the
glue nozzle even though we tried every epoxy and tape in our arsenal.
As Paul eluded to in a previous post, the tips did not touch the board but
the stand-off did.
Scott
-----Original Message-----
From: [log in to unmask]
[mailto:[log in to unmask]]
Sent: Monday, August 16, 1999 2:47 AM
To: [log in to unmask]
Subject: Re: [TN] clogging dispensers
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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