Gary, you've already received several good comments, including a clarification from Werner regarding temperatures. I'm providing an additional clarification.
You reference reflow profiles from J-STD-020, the MSD classification test method/standard. J-STD-020 clearly states that the profiles provides are specific to the component MSD classification process. The listed profiles are NOT intended for and in many cases will NOT WORK for assembly reflow.
IPC-7530 Guidelines for Temperature Profiling for Mass Soldering Processes (Reflow & Wave) is a good support document to help you through the profiling process. (Werner is leader of the committee that maintains this document.)
Jack Crawford
IPC Director Certification and Assembly Technology
________________________________________
From: Leadfree [[log in to unmask]] On Behalf Of Gary Koven [[log in to unmask]]
Sent: Friday, June 26, 2009 11:08 AM
To: Listserv Leadfree
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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