The evolution of organic solderability preservatives (OSP) from a temporary protectant to a leadership position in surface finishing chemistry

Abstract

Purpose

The purpose of this paper is to present an overview of the evolution of organic solderability preservatives (OSP) technology from a temporary anti‐tarnish to an approved process for the lead‐free assembly of high‐reliability printed circuit boards (PCBs).

Design/methodology/approach

As this is an informational paper, the main approach was to compare and contrast various types of OSP molecules and their fitness for use.

Findings

The active ingredient of an OSP is one of the most important ingredients that can help to improve the heat resistance, which becomes much more important in conjunction with lead‐free solder. The latest OSP shows excellent stability, even at more than the peak reflow temperatures used with lead‐free solders. The success of any OSP process is highly correlated to process control and maintenance and OSP formulations are not created equal. The thickness of the film is only one difference. However, the key differentiators for OSP coatings are the overall ability of the organic film to resist oxygen penetration and humidity; and withstand the higher temperatures of lead‐free assembly. The author suggests that original equipment manufacturer (OEMs), contract manufacturers and PCB fabricators perform testing and qualification of OSPs using industry‐accepted reliability and solderability testing methods.

Research limitations/implications

This work represents the author's extensive experience with OSP technology, as well as the results of a collective collaboration with Shikoku Chemical Corporation. The findings represent reliability and solderability testing carried out in various manufacturing sites including cooperation with certain OEMs that are users of circuits fabricated with OSP technology.

Originality/value

This paper details how critical advances in OSP technology have enabled improvements in solderability and reliability over earlier commercial generations and have further enhanced the solderability of lead‐free assemblies.

Citation

Carano, M. (2011), "The evolution of organic solderability preservatives (OSP) from a temporary protectant to a leadership position in surface finishing chemistry", Circuit World, Vol. 37 No. 2, pp. 12-19. https://doi.org/10.1108/03056121111128279