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Solder paste ProFlow issue

Does the problem reduce if you print with less shear stress (reduced pressure, lower head speed) on the DEK? Shear-thinning in the paste could add to the lower viscosity problems caused by elevated temperature.

Leo

-----Original Message-----
From: Henry Rekers [mailto:[log in to unmask]]
Sent: Wednesday, September 25, 2002 9:14 PM
Subject: Re: Viscosity vs Temperature.

Yes you can, our machine came with a proflow and sqeegee head. You just have to power cycle the machine to go from one to the other. (Plus change heads - a couple of bolts and a few connectors.)

-----Original Message-----
From: Steve Gregory [mailto:[log in to unmask]]
Sent: Wednesday, September 25, 2002 5:02 PM
To: [log in to unmask]
Subject: Re: [TN] Viscosity vs Temperature.

Hi Henry!

I don't have any answers to your dilema, but your post does bring up some questions...

Once you have ProFlow installed on the printer, can you go to regular squeegees if you need to? I know I could call DEK and find that out, but I like to hear from us guys...

I have a DEK-288, and I can get it retro-fitted with ProFlow, but I wonder if things go haywire, can I go back to analog=squeegees.

This is something that I've thought about with my new wave solder...I've got an Electrovert Electra...everything is computer controlled...so if my computer crashes on the machine (It's Windows NT, makes me feel a little better...) I'm basically DIW...sorry, Navy term (Dead In the Water).

-Steve Gregory-

We are having some issues with a new solder paste. The evaluations came out
extremely well at first. However, upon using it for some trial runs, we run
into some problems.

In our DEK profolw the prints look very good at about 20 deg C. Throughout
the day, the temp in our facility climbs to 28 or even 30 deg C. The prints
then start to bridge and flux bleeds out onto the board. We can compensate
for it to about 25 deg by reducing the proflow pressure and wiping on every
print, but beyond 25 deg, nothing helps.

By the time the 3rd shift rolls in, the temperature starts to drop again and
the prints become more managable again.

Here's the kicker, we use this same paste on our MPM with squeegee's and the
print works every time. There is never a print problem vs temperature.

Has anybody ever run into this situation? How did you solve it?

Thanks in advance.

Henry J. Rekers
Manufacturing Engineer
Power Measurement.

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