Dear Mr. Le,

We are trying to study some of the process issues here at University of
Massachusetts Lowell. It's too early to conclude something about it as we
are still in the testing phase. however   I can share some of  the profile
details we used in the assembly of test boards .

We used profiles with soak and without soak. the peak temperature is almost
the same as yours, 235 for Sn/Ag/Cu.
but the rise time between 150 and 170  for the soak profile was 90-120sec.

We tried three different time above liquidus: 60 sec, 90 sec and 120 sec.
We still have to complete the tests but It seems to me that only 40 second
above liquidus  may be very low for Sn/Ag/Cu . It has been found that
increasing the liquidus time to certain extent does enhances the wetting
performance of lead free solder.

It may also appear that it's not at all necessary to go with the soak
profile. The linear profiles may be better than the conventional preheat
soak time profiles.

Regards,

Hemant Belbase
26 West Street # 1
Malden, MA 02148
781-322-6557
[log in to unmask]

-----Original Message-----
From:   Le Ai Quoc [SMTP:[log in to unmask]]
Sent:   Thursday, April 27, 2000 12:51 AM
To:     [log in to unmask]
Subject:        [LF] Lead-free solder paste

Dear Sirs,
Thank you very much for your precious information about lead-free solder
paste. We are Fujitsu Vietnam and we are now, facing to temperature profile
of Lead-free solder paste. The most difficulty is that the range of
acceptable peak temperature is 10oC only: Peak temperature must be within
225oC ~235oC.

The lead-free solder paste we are trying on is supplied by 2 Japanese
Makers:
- Senju
- Alphametals
Specification of this solder paste: Sn/3.0Ag/0.7Cu; melting point: 217oC

We still use the same profile spec. to apply this solder paste to our
products:
+ Time within 130~160oC must be from 60~180sec. only
+ Time over 210oC must be within 40sec. only
+ Peak temp. must be within 225oC~ 235oC or in max. 235oC within 5sec. only

For what I have just mentioned above, please teach us the following
queries:
1.We heard that you are using the ANSIJ-STD-020A. Would you be kind enough
to e-mail us that one for our reference?
2. If possible, please give us your opinion about our profile criteria.
(ex: too tight?...)
Very highly appreciate your quick reply. If you need more information,
please inform us.
Thank you very much for your help
Best regards,
Le Ai Quoc
*************************************************************************
Fujitsu Computer Products of Vietnam (FCV)
E-mail: [log in to unmask]
PCBA Engineering section - PCBA Manufacturing Department
Tel: 84-061-836563 ~ 6 / Ext: 214 - Coins: 79691-214
Fax: 84-061-836561 ~ 2 - Coins: 79691- 109 / 209
**************************************************************************

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