Jeffrey C. Suhling, H.S. Gale, R. Wayne Johnson, M. Nokibul Islam, Tushar Shete, Pradeep Lall, Michael J. Bozack, John L. Evans, Ping Seto, Tarun Gupta and James R. Thompson
The solder joint reliability of ceramic chip resistors assembled to laminate substrates has been a long time concern for systems exposed to harsh environments. In this work, the…
Abstract
The solder joint reliability of ceramic chip resistors assembled to laminate substrates has been a long time concern for systems exposed to harsh environments. In this work, the thermal cycling reliability of several 2512 chip resistor lead‐free solder joint configurations has been investigated. In an initial study, a comparison has been made between the solder joint reliabilities obtained with components fabricated with both tin‐lead and pure tin solder terminations. In the main portion of the reliability testing, two temperature ranges (−40‐125°C and −40‐150°C) and five different solder alloys have been examined. The investigated solders include the normal eutectic Sn‐Ag‐Cu (SAC) alloy recommended by earlier studies (95.5Sn‐3.8Ag‐0.7Cu), and three variations of the lead‐free ternary SAC alloy that include small quaternary additions of bismuth and indium to enhance fatigue resistance.
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Andrew J. Hobson, Linda J. Searby, Lorraine Harrison and Pam Firth
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…
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.