Guenter:
What is the coating that you will use to coat your solder pot?
Thanks,
Tom Woodrow
The Boeing Company
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-----Original Message-----
From: Guenter Grossmann [mailto:[log in to unmask]]
Sent: Wednesday, July 10, 2002 1:56 AM
To: [log in to unmask]
Subject: [LF] Antw: [LF] Lead-free Issues
Yea Joe
- Well I do agree that the ecologic sense of abandoning lead is in question.
From our colleagues in the IZM Berlin who do life cycle analysis I heard
that the lead free issue is at the minimum environmentally neutral but more
on the beneficial side. But, as we all know, each model lives from its
inputs. However, we have to start somewhere.
- With recapitalization I believe you talk about new equipment. I hope my
project members don't mind too much if I tell you that when it comes to
reflow you don't necessarily need new equipment. With the process parameters
we tried successfully we where in the process windows used in industry for
PCB's with a high thermal demand. Some points are:
. You need a good process control, since the process window gets smaller
this implies that pure IR- equipment will make problems
. Sealings in N2 equipment will need more frequent replacement
. Ball bearings of the motors without a cooling fan will break down (seems
to be a lubrication problem)
. Some convection ovens have the electronics close to the process chamber.
This will lead to overheating
Generally one can say that you can use old convection equipment with an
enhanced need of service.
. Wave soldering equipment does need replacement due to tin corrosion. Or
you can cover all parts that are in contact with the solder with an
appropriate paint that should do the job for 2-3 years we will try that
soon.
- Recycling of a ternary system (SnPgAg) is already possible and to my
knowledge also done . I believe we will find a process that enables the
reclaim of Tin, Copper and Silver. The crux is that we have to start rather
than lamenting about sense and nonsense of leadfree. I see it whenever I am
about to start a project in any field of lead free soldering. There is more
discussion about when will the European legislation come, how log can one
wait until the legislation is in force what are the exceptions etc etc. To
come to the technical problems is quite hard and to find any financing even
more (surely also, as you mentioned ,due to the present economic condition
of industry)
- Regarding components I must say that we did wave soldering with 250 deg.C
solderpot temperature and convection soldering with 235 deg.C measured at
the pin of a SOP. As you see, quite close to liquidus. Again this calls for
good process control. However, I have to admit, that we didn't work with
LED's since this makes only sense with an estimation of the failure rate
after soldering. And, even if I stress this too much: Who pays for that?
- Yes, I do think LF is the place to discuss sense or not of lead free
soldering. and it was never my intension to question that.
Cordially
Guenter
EMPA
Swiss Federal Institute for Materials Testing and Research
Centre for Reliability
Guenter Grossmann, Senior Engineer
8600 Duebendorf
Switzerland
Phone: xx41 1 823 4279
Fax : xx41 1823 4054
mail: [log in to unmask]
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