Electronics Assembly Knowledge, Vision & Wisdom
Human-Induced Contamination on PCB Assembly
Human-Induced Contamination on PCB Assembly
This paper will discuss an experiment that was performed to investigate the effects of "contaminants" that could be measured with SIR testing.
Analysis Lab

Authored By:
Eric Bastow
Indium Corporation
Clinton, New York
,{url:'http://www.circuitinsight.com/videos/programs_final.mp4'}], clip:{autoBuffering:true, autoPlay:true, scaling:'scale' } }).ipad();
With the ever-present pressure toward miniaturization in electronic devices, smaller distances between traces and component terminations are likely to increase the devices' sensitivity to contamination scenarios that may cause current leakage. Traditionally, with "no-clean" processes, the focus has been on the conductivity of flux residues, which can be measured with industry accepted techniques such as IPC J-STD-004B SIR (Surface Insulation Resistance) testing (IPC-TM-650

However, the manufacturing environment, especially in low-cost labor markets, and even on otherwise well-controlled shop floors, may be far from representative of the "perfect world." Other materials may find their way on to the surface of the PCB, often introduced through negligent human activity and handling that may or may not have a negative impact on the electrical reliability of the device.

This paper will discuss an experiment that was performed to investigate the effects of "contaminants" that could be measured with SIR testing. The contaminants were tested by themselves as well as in conjunction with a halogen-free, Pb-free, no-clean solder paste. The materials investigated as contaminants were: human skin oil/perspiration, high temperature reflow oven chain oil, pepperoni pizza grease, hand cream/lotion, and tap water.
The message that these experiments provide is that contamination has the potential to reduce the surface insulation resistance (SIR) of an assembly. The level of reduction may or may not create a reliability issue. However, it is important to note that the test vehicle has 0.4 mm lines and 0.5 mm spaces and tested at 5 VDC. One has to ask the question, if contamination produces a measurable reduction in SIR performance in these test conditions, what is the impact if the spacing is smaller and/or the voltage is higher? In such cases, the level of tolerance toward contamination could be, and should be, much less.
Initially Published in the IPC Proceedings
Submit A Comment

Comments are reviewed prior to posting. Please avoid discussion of pricing or recommendations for specific products. You must include your full name to have your comments posted. We will not post your email address.

Your Name






Please type the number displayed into the box. If you receive an error, you may need to refresh the page and resubmit the information.

Related Programs
bullet What Causes Board Delamination?
bullet Sticky Residue Under Low Clearance Parts
bullet Head in Pillow Explained
bullet Surface Mount Warpage Case Study
bullet Tin Whisker Testing and Modeling
bullet LED Component Shift During Reflow
bullet Innovative BGA Defect Detection Method for Transient Discontinuity
bullet Contaminated Joints Cause an Assembly to Fail RoHS Compliance
bullet Risk and Solution for No-Clean Flux Not Dried Under Components
bullet Dust contamination after selective soldering
More Related Programs