I agree with Werner. We've been using an Asscon machine for nearly 4 years now and it has been amazing compared to convection. We are using a SAC solder paste and can keep the ramp below 2C/s with a ramp to spike profile. We couldn't be happier with the results.
Regards,
Larry
BTW - I would also include R&D Tech to the list of capable machines.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: Friday, January 14, 2011 6:53 AM
To: [log in to unmask]
Subject: Re: [TN] Trace Widths Entering SMT
Hi Mike,
The shape of the reflow profile, mostly ramp-soak-spike, comes from the heat transfer needs to minimize T-differences at the spike and peak regions.—and things certainly have gotten worse with Pb-free.
The flux chemistries can be adjusted to these heat-up shapes. To make consistent good quality solder joints it is the peak reflow T that is most important, but it is also this peak T that causes the damage in PCBs and components.
VPR machines have come a long way since early machines gave VPR a bad name—you really need to take a look at these machines with controlled programmed vapor fluid injections and other operating features. The machines from the 3 main VPR machine suppliers (Rehm, IBL, Asscon) are quite amazing and very capable.
And they make it possible to properly solder even very large BGAs with SAC solders at very much lower T's than is possible with multi-zones.
So, I stand by my statement.
Werner
-----Original Message-----
From: Mike Fenner <[log in to unmask]>
To: 'TechNet E-Mail Forum' <[log in to unmask]>; 'Werner Engelmaier' <[log in to unmask]>
Sent: Fri, Jan 14, 2011 5:36 am
Subject: RE: [TN] Trace Widths Entering SMT
Morning Werner
HNY
May I respectfully question your statement below?
I am a big fan of VPR/Condensation reflow and was instrumental/involved in
its European debut installing the first machines and working with 3m HTC
etc. but even I would not have been quite as unequivocal as you below.
The reduced delta T at peak and inherent temperature limitation are
advantageous and stem from the equilibrium nature of the heating process.
The load independent nature of the process is also important.
However IMHO the real key to successful reflow is controlling the profile
shape rather than peak. VPR is poor in this respect, compared to convection
ovens.
VPR is not the only equilibrium process, some of the more efficient
Convection machines can also run in equilibrium (easily demonstrated by
leaving a thermocouple from profiler free floating) and being multi-chamber
are much easier to profile than a single chamber VPR machine.
The natural ramp rate of a saturated VPR process is about 50C/second and
trying to control this to <4C is difficult and compromises some of the VPR
attributes.
I am trying to setup a small investigation on VPR here in UK with the object
of writing an article or possibly a paper and hopefully will have some more
light to shed.
Meanwhile I would appreciate your comments.
Regards
Mike
ü Please consider the environment before printing this e-mail
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: Wednesday, January 12, 2011 8:08 PM
To: [log in to unmask]
Subject: Re: [TN] Trace Widths Entering SMT
Vapor phase is better than any other heating method for two reasons: (1) no
over-temperature possible, (2) more uniform heating.
Werner
-----Original Message-----
From: Ioan Tempea <[log in to unmask]>
To: [log in to unmask]
Sent: Wed, Jan 12, 2011 10:54 am
Subject: Re: [TN] Trace Widths Entering SMT
No do Carl,
IR or convection do not bring everything at temperature at the same time.
Don't
know about vapour phase though.
Imbalance is an important cause for tombstoning.
Regards,
Ioan Tempea, ing.
Ingénieur Principal de Fabrication / Senior Manufacturing Engineer
T | 450.967.7100 ext.244
E | [log in to unmask]
W | www.digico.cc
N'imprimer que si nécessaire - Print only if you must
-----Message d'origine-----
De : Carl VanWormer [mailto:[log in to unmask]]
Envoyé : January-12-11 10:50 AM
À : [log in to unmask]
Objet : Re: [TN] Trace Widths Entering SMT
Novice question . . .
I was told that the heating imbalance "goes away" in the IR reflow
process, since "the whole thing" has been brought up to temperature at
"the same time".
Question: can we "mostly ignore" potential thermal imbalances caused by
asymmetrical traces shape/width for IR reflow process boards? (or have
I been lied to, again . . .)
Thanks,
Carl
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