Bill, I am sorry to hear that you have had problems with dispensing solder
paste.
I hope that there are some netters out there who will relate their
successful experiences, this will possibly be more relevant to you than my
reiterating that it can be done - "he would say that wouldn't he".
Nevertheless I will reiterate that high speed dispense of solder paste
(X0,000 dots per hour) is practical provided that attention is paid to
specifying the right paste criteria.
It sounds as though you might have been badly advised in this respect, the
most common fault is to get the particle size wrong, this is set by the
smallest geometry in the dispense path, not just the needle ID. In addition
changes in the dispense path geometry may need to be reviewed as shear
characteristics of some pastes to adhesives may also be different. This
whole area is much more critical in solder paste applications than with
adhesives, due to the generally larger size of the solder balls compared to
adhesive fillers.
To oversimplify moderately: solder pastes have to be a compromise in this
method of application, the crucial difference between solders and adhesives
is that on heating to make a bond the solder particles are expected to join
back together to make a single fillet, [in adhesives they remain unchanged].
The smaller the particle the harder this is to do, there comes a time when
the paste won't work. This size has shrunk over the years but still remains
larger than typical adhesive filler particles.
Now I don't want to get into a commercial here. Perhaps we can talk offline?
Or better, one of my US colleagues - [log in to unmask] - can talk with you
on this, define with you your requirements and process and make an
appropriate recommendation to proceed or not, maybe what you want can't be
done.
Mike Fenner
Indium Corporation of Europe
www.indium.com
-----Original Message-----
From: Kasprzak, Bill (sys) USX [mailto:[log in to unmask]]
Sent: Tuesday, June 12, 2001 12:36 PM
To: [log in to unmask]; 'IPC-Tech Net'
Subject: RE: [TN] Looking for a "special" solder paste dispenser
Hello all,
I've been watching this thread for a few days now hearing about how solder
paste can be dispensed from an automated system.
My experience has not turned out very well with only very limited success.
We have a Camalot 1414, even bought the special displacement pump designed
for this application and attempted to dispense solder paste. I just could
not get the system to be repeatable. Once I had a set up, repeating the next
day or even the next hour was impossible. I tried different pastes,
different particle sizes, needle sizes, etc. etc. One of the biggest
problems that I had was coining. This is where the particles compressed to
form a solid plug where the paste entered the dispensing needle.
I gave up on this method, settling instead on using microstencils to apply
paste.
I would like to know of anyone who has had success with dispensing solder
paste. I would like to know some particulars about the process. (paste,
needle size, pump pressures, etc) I would not mind trying this again if I
could just get some help with this.
However, if you've never done this and you're thinking that this is a viable
process, I am advising to be very careful about sales pitches that claim
that solder paste dispensing can be done. I don't think that it is a
repeatable process.
Bill Kasprzak
Moog Inc., Electronic Assembly Engineering
> -----Original Message-----
> From: Mike Fenner [SMTP:[log in to unmask]]
> Sent: Tuesday, June 12, 2001 3:47 AM
> To: [log in to unmask]
> Subject: Re: [TN] Looking for a "special" solder paste dispenser
>
> Solder paste can be dispensed quite well from these systems provided that
> proper attention is paid to correctly specifying the material. Solder
> pastes
> are inherently more difficult to dispense than adhesives but if particle
> size range [and distribution in the specified range] is correctly done
> with
> the right vehicle rheology, consistent dispense at quite high rates is
> achievable.
>
> Mike Fenner
> Indium Corporation of Europe
>
> Hi, Craig,
>
> You could try Asymtek, part of the Nordsen group, which specialises in
> fluid dispensing technology. They seem to be the market leaders. They do
> underfill, adhesive and flux dispensers, and though I haven't seen a
> solder
> paste dispenser in their list, they may do one. Or try EFD - they do have
> a paste dispenser, but you'll need to decide its accuracy for yourself.
>
> Pete Duncan
> Hello Technetters,
>
> For research and development purposes, I am looking for a machine that
> dispenses solder
> onto a board WITHOUT the use of a solder stencil. The speed is not as
> important as accuracy and
> quality of work.
>
> Do you know of a machine like this? If so, how can I find one?
>
> Thanks for your help,
> Craig
>
---------------------------------------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
---------------------------------------------------------------------------------
|
