Hi Wade,
We are using a Camalot Gemini dispensing system. I being the most sceptical
out of Paul Klasek and myself am now very much sold on dispensing systems
for Sodder Paste as you guys call it. It has totally blown away my theories
a had about screen printing. To give you some of the Benefits,

The good Points

1: Solder Paste Wastage calculated at 4% (Call me inefficient but we had
approx 30% with screen printing in past lives).
2: Safety, operators prefer handling the tubes and is very clean with no
mess.
3: Deposition Control. Ever had the problem where you wanted to control the
amount paste using stencils but could not or were limited due to fine pitch
constraints and aspect ratios (Stepped stencils can be a nightmare). It is
interesting to note that coplaniarity issues with finer pitch devices and
other IC's are negated dut to the dot height which eliminates dry joints due
to coplaniarity issues.
4: Flexibility with regards to frequent design changes, no need to buy
multiple stencils through alpha, beta and production stages.
5: No cleaning of stencils or blocked apertures.
6: Paste rheology does not play a large role in dispensing negating the need
to constantly work the paste during screen printing to achieve a consistant
deposit (Mainly concerned with fine pitch)
7: Change over time between one product and another is as quick as loading
another program and changing the Conveyor width (Again no need for stencil
maintenance).

The Not so Good Points

1: The solder paste is more expensive for -400 to +500 Mesh (Negated
somewhat buy the wastage and waste handling but unfortunately the
accountants do not see this, I suspect it has something to do with the
personality bypass operation they have after certification)
2: Programming can take a couple of hours to do depending on how many
components there are but compared to stencils if you take into account the
time taken to do aperture reductions and adjustements creating gerbers
emailing them to stencil suppliers liasing with stencil suppliers creating
purchase orders la di da etc etc programming time is not as bad as you first
imagine.
3: You do sometimes get a missing dot here and there but nothing of major
concern a little process control fixes this.
4: It is slower than screen printing, you can not put them in front of fast
chip shooters and utilise SMT machines effectively. We are on our boards
getting approximately 70% of tact. So please note it depends on your
production requirements, we are currently looking at buying the fastest
dispenser on the market to take up this issue.

These are some of the more obvious things which may be food for thought and
help in the decision making process.

Regards

Zoran Raich
ResMed Ltd
www.resmed.com.au

> ----------
> From:         Wade Oberle[SMTP:[log in to unmask]]
> Sent:         Wednesday, February 03, 1999 3:13 AM
> To:   [log in to unmask]
> Subject:      [TN] SMT dispensing systems
>
> Dear Technetters,
>         I'm interested in who are the 'major players' in the SMT
> dispensing business.  In my opinion, Camalot and Asymtek are on the top
> tier.  I'd be interested to here other opinions and experience.
>
> Regards,
>
> Wade Oberle
> 414-947-3477
> [log in to unmask]
>
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