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Johanson Ceramic Capacitors Forward/Backward Process Compatibility
John Maxwell, Director of Product Development
March 1, 2006 |
The standard termination finish for Johanson ceramic capacitors is matte tin over nickel.
Tin lead (SnPb) plating is available on special and is typically supplied for aerospace and
other high reliability industries that require lead (Pb) in the termination finish.
The questions that can arise is can matte tin plated over nickel be soldered with standard
SnPb solder profiles. Matte tin on the termination is rapidly dissolved into either SnPb or
lead free (LF) solder alloys forming a reliable solder joint. The solder joint is formed
between the solder alloy and base metal on the capacitor termination and requires no
change in solder profiles. The following is a set of general soldering guidelines for
termination finishes and solder alloys and is summarized in Table 1. |
| 1) |
Lead free termination finish components are compatible with both LF and Pb
bearing solder |
| 2) |
Components using Pb bearing lead finish are not compatible with LF reflow
solder assemblies and can poison or contaminate LF solder pots. |
| |
| a) |
A thin Pb bearing zone forms near the lead containing Pb during reflow
soldering and freezes later than bulk of the solder joint |
| b) |
At this point all of the shrinkage stress is concentrated in the thin Pb zone
and can result in solder joint cracks |
|
| 3) |
Pb bearing subassemblies are compatible with LF soldering temperatures |
| 4) |
LF subassemblies are usually not compatible with standard Pb based solder
reflow profiles due to degradation of LF solder joints (See ** below) |
|
| Notice: Specifications are subject to change without notice. Contact your nearest Johanson Dielectrics
Sales Office for the latest specifications. All statements, information and data given herein are
believed to be accurate and reliable, but are presented without guarantee, warranty, or responsibility
of any kind, expressed or implied. Statements or suggestions concerning possible use of our products
are made without representation or warranty that any such use is free of patent infringement and are
not recommendations to infringe any patents. The user should not assume that all safety measures are
indicated or that other measures may not be required. Specifications are typical and may not apply to
all applications. |
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