When speaking of reflow time temperature profiles I always am speaking of
measured temperatures on the board at the solder connection.
I don't think you can get an apples to apples comparison of oven air
temperatures for a couple of reasons.
1. The oven temperatures are measured at different locations brand by brand,
model by model.
2. The conditions of convection result in different thermal transfer
performance in different ovens.
We have used, as a our preferred WS paste, a Japanese formula by Tamura.
I agree with what you said below. In some ovens the set point required to
achieve and acceptable TTP is even higher than below, 290°-320°C. It might
be possible to achieve reasonable reflow results on thin boards with easy to
heat parts and oven settings in the 250°C range.
I wonder if there is a communication gap between you and your colleagues in
Japan, unless they are using a Bi fortified alloy.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
Sent: Tuesday, March 24, 2009 9:22 AM
To: [log in to unmask]
Subject: Re: [TN] Low temp RoHS solder paste
Is that 250 the oven set point of the measured PCB Temp?
To get a good "Spike" in the reflow profile you need a fairly hot oven. If
you set the oven anywhere near 250 you get a slow ramp to 250 which burns
off the flux.
I have played with SnPb and just a little with SAC. But I recall 260 or 270
as the oven set point in the "Spike" zone. And this is a real pin for the
fluxes which burn off quickly on hot areas.
I never liked the SAC and hot air reflow, the process window was much
smaller than SnPb. A vapor phase reflow gives you a really tight control
over temp, much more than hot air. But vapor phase is more expensive.
Bob Kondner
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Guy Ramsey
Sent: Tuesday, March 24, 2009 9:08 AM
To: [log in to unmask]
Subject: Re: [TN] Low temp RoHS solder paste
Pretty standard stuff Doug.
SnPb below 220°C and PbFree above 240°
250° is definitely not low temp.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Erb
Sent: Monday, March 23, 2009 11:59 AM
To: [log in to unmask]
Subject: [TN] Low temp RoHS solder paste
In Asia, many CEMs are successfully applying components using RoHS
compliant solder pastes at 250C max temps in their ovens; so I've been
told by my colleagues in Japan. They do not have sourcing info on the
paste suppliers, however. Is anyone out there familiar with the
practice and if, indeed, there are new solder alloys that are capable of
achieving Class 3 wetting integrity at 250C?
Doug Erb,
Senior FAE
Hirose Electric USA
Industrial Segment
Office direct: (949) 218-3445
Fax direct: (949) 218-3425
Mobile: (949) 463-8447
Main office: (805) 522-7958
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