Hi Gary - a couple of comments: (1) IPC -JSTD-002 is a solderability test 
specification and is not relevant to your reflow questions in terms of 
temperature range; (2) You will find there a two industry camps  - the 
camp that says "don't subject" tin/lead components to a leadfree reflow 
profile because the components are not qualified for that process exposure 
and the camp that says "do subject" tin/lead components to a leadfree 
reflow profile but keep the temperature exposure as limited as possible in 
terms of maximum temperature and duration. A product design team, in 
conjunction with the component engineering team, need to determine if the 
Camp 2 option is viable for their product. Good Luck.

Dave Hillman
Rockwell Collins 
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Gary Koven <[log in to unmask]> 
Sent by: Leadfree <[log in to unmask]>
06/26/2009 11:08 AM
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Gary Koven <[log in to unmask]>


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Subject
[LF] Reflow profiles for mixed Pb status boards






For those of you who subscribe to the IPC DesignerCouncil email forum, 
this will be a duplicate topic...

We have a number of PCBAs with both leaded and lead-free parts on them.

Looking over the J-STD-020 reflow profiles on one of the leaded part 
datasheets, we saw that its range seemed too restrictive for the lead-free 
profile.

Basically the two parameters that interest us are:

(1) Preheat temperature, 100 oC-150 oC for leaded and 150 oC-200 oC for 
lead-free

(2) Liquidous temperature, 183 oC for leaded and 217 oC for lead-free.

On our assembly drawings we call out IPC-A-610 Class 2.  I understand that 
J-STD-002 can also be used together with IPC-A-610 as a note callout.

Since there is not a RoHS-compliant requirement for these boards, we don't 
call out what type of solder process needs to be used.

We're curious about how assembly shops adjust their soldering process for 
boards that have both types of parts on them.

We're also wondering whether we need to begin calling out specific solder 
processes, but we don't want to add cost to the assembly.

Give me a solution that doesn't add cost to the assembly, but at the same 
time satisfies the curious, please.

TIA and Best Regards,

Gary M. Koven, C.I.D.
Dynazign, Inc.
Charlotte, NC, USA
Veteran of the Marsh School

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