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Packaging | Lead-Free Status | Impact to Customers | Tin Whiskers
European Dir. Compliance | Industry Consortia | Questions & Answers | Literature
Impact to Customers
Forward/Backward Compatibility
Definitions:
- Backward compatibility: A lead-free component is said to be backward compatible if it can be reliably attached to a PCB using tin/lead solder paste with a tin/lead solder profile (typical peak reflow temperatures ranging from 220°C to 235°C).
- Forward Compatibility: A SnPb component is said to be forward compatible if it can be reliably attached to a PCB using lead-free solder paste with a lead-free profile (typical peak reflow temperatures ranging from 240°C to 260°C).
- For leadframe-based surface mount packages1,2
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Lead finish |
Reflow Process and Peak Temperature Range |
|
Tin/Lead Process (220°C - 235°C) |
Lead-Free Process (240°C - 260°C) |
|
Tin/Lead (SnPb) |
OK |
OK if device ordered with suffix 260°C (forward compatible) |
|
Lead-free (matte Sn) |
OK (backward compatible) |
OK | 1. Based on board level evaluations, it is recommended that a reflow temperature of 235°C be used for LLP® backward compatibility (SnPb solder paste/Pb-free components).
2. Through-hole packages have not been evaluated for forward or backward compatibility.
- For micro SMD and BGA packages
|
Solder bump/ball composition |
Reflow Process and Peak Temperature Range |
|
Tin/Lead Process (220°C - 235°C) |
Lead-Free Process (240°C - 260°C) |
|
Tin/Lead (SnPb) |
OK |
NOT RECOMMENDED
(not forward compatible) |
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Lead-free (SnAg [BGA] or SnAgCu [micro SMD]) |
NOT RECOMMENDED
(not backward compatible) |
OK |
Reflow Profile
- Generally, the reflow profile will depend on the melting point of the solder paste and the geometry and layout of the PCB.
- With sufficient engineering characterization, the throughput for the Pb-free profile can be made the same as that of the SnPb profile.
- For lead-free qualification, National used the Pb-free profile given in J-STD-020C. This profile is also acceptable for production, provided that adequate characterization is done by the board level assembler.
Tin Whiskers
- Tin whiskers are recognized as a reliability concern throughout the industry.
- To mitigate whisker growth National has done the following:
- Established the minimum plating thickness of 8 microns, with a nominal thickness of 12 microns.
- Established a post-plate annealing of 1 hour at 150°C within 24 hours of plating.
- Additional information is available on the Tin Whiskers page.
Packaging | Lead-Free Status | Impact to Customers | Tin Whiskers
European Dir. Compliance | Industry Consortia | Questions & Answers | Literature
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