(electro) Ipc 4554 Specification For Immertion Tin Plating For Printed Circuit Boards (final Draft Ii).pdf

IPC-4554
January 2006






Specification for
Immersion Tin Plating
for Printed Circuit Boards

FINAL DRAFT II

[By: 4-14 Plating Processes mittee]
















Proposed by IPC
2215 Sanders Road,
Northbrook, IL 60062
Phone : (847) 509-9700
Fax : (847) 509-9798
URL :
Scope

This specification sets the requirements for the use of Immersion Tin (ISn) as a surface finish for
printed circuit boards. This specification is intended to set requirements for ISn deposit thickness
based on performance criteria. It is intended for use by supplier, manufacturer, contract
manufacturer (CM) and original equipment manufacturer (OEM).

Description

ISn is a metallic finish deposited by a chemical displacement reaction that is applied directly over the
basis metal of the PWB, copper. Primarily used as a solderable surface. It has been used in press
fit connections and as the interface for Zero Insertion Force (ZIF) edge connectors.

The immersion tin protects the underlying copper from oxidation over its intended shelf life. Copper
and tin however have a strong affinity for one another. The diffusion of one species into the other will
occur inevitably, directly impacting the shelf life of the deposit and the performance of the finish.

The latest generation of immersion tin deposits utilize various methods of retarding the diffusion
process, including the use of co-deposition anics, the use of another metal as a diffusion
barrier or the use of grain structure refining. It is mended that the user of the deposit clearly
understand the different methods of copper migration retardation and that the supplier know the
positive and negative impacts of the system chosen.


Objective

This specification sets the requirements specific to ISn as a surface finish. As other finishes require
specifications, they will be addressed by the IPC