JOHANSON DIELECTRICS INC.

15191 Bledsoe Street, Sylmar, Ca. 91342 Phone (818) 364-9800 Fax (818) 364-6100

1 March 2006 Rev 1.01

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Johanson Ceramic Capacitors Forward/Backward Process Compatibility

John Maxwell, Director of Product Development

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)

Table 1. Lead Finish Solder Process Compatibility

Component Lead Finish SnPb Reflow Process LF Reflow Process

(Tin Lead) (Lead Free)

Pb Bearing Component

Leads or SnPb Soldered Yes Yes*

Subassembly

Lead Free Finish Yes Yes

Lead Free Sub Assembly No** Yes

* Depending on reflow solder time and peak temperatures tin lead solder will

mix with lead free solder resulting in an intermediate lower temperature alloy

near the Pb bearing lead or termination.

** Lead free solder joints may reach the solders melting point resulting in very

weak joints, complex heat sinking and or shields will be required. This is due

to different phases forming that can have slightly different melting/freezing

points that can form small cracks within the solder joint during cool down.

JOHANSON DIELECTRICS INC.

15191 Bledsoe Street, Sylmar, Ca. 91342 Phone (818) 364-9800 Fax (818) 364-6100

1 March 2006 Rev 1.01

1/2

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.