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September 22, 2025 - Updated March 3, 2015 - Originally Posted PCBA Inspection Process Causing DamageWe inspect PCBAs on a relatively hard ESD mat surface. QA claims that during inspection, moving of the PCBAs on the mat will scratch and stress the soldered components (bottom side). Are there any studies on this matter? Are there any dedicated tools in the market designed for this purpose? T.S. |
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I am not aware of any specific studies that were done on the movement of a PCB on a"relatively" hard mat causing damage to bottom side components. It stands to reason that the use of a mat, properly grounded, is a benefit to the board. Typically any mat being used will have a softer surface than the laminated work surface of the bench. If your operators are sliding the PCB across the surface then, yes, there is a potential for damage. Just placing a PCB on the surface should not cause any issues. If you have concerns about damage I would suggest switching to a homogeneous vinyl material which is typically a softer surface. Be aware that this type of material cannot be used with a constant monitoring system as there is no conductive layer.
President JSK Associates Based in. Northern California since 1971. Founded JSK Associates in 1979. Actively involved in soldering, cleaning, chemistries. 30 years experience in EOS/ESD control.
True .Moving the PCBA on a hard surface will sometimes scratch components, and stress soldered joints. There are many table-top inspection stations on the market designed to avoid damage to the assemblies. The common setup is a stationary rail that holds the PCBA. Other most advanced fixtures come equipped with a camera in order to display the images on a monitor.
Senior Manufacturing Engineer Northrop Grumman Edithel is a chemical engineer with 20 year experience in manufacturing & process development for electronic contract manufacturers in US as well as some major OEM's. Involved in SMT, Reflow, Wave and other assembly operations entailing conformal coating and robotics.
I'd agree that any time we slide a PCBA across a surface, there is some risk. If the surface is clean and smooth, that risk is absolutely minimal unless very sensitive components are involved. If your QA folks can provide quantifiable evidence that there is a risk, then one approach would be to use a carrier to which the PCBA is affixed and inspect while in the carrier. In this way, all contact with the bench is eliminated. Another benefit is that the PCBA can beheld precisely level and at a known height, which might be important if you are inspecting under stereo microscopes. I'm envisioning an adjustable metal frame with feet to support the board off the table.
Process Engineer Astronautics Fritz's career in electronics manufacturing has included diverse engineering roles including PWB fabrication, thick film print & fire, SMT and wave/selective solder process engineering, and electronics materials development and marketing. Fritz's educational background is in mechanical engineering with an emphasis on materials science. Design of Experiments (DoE) techniques have been an area of independent study. Fritz has published over a dozen papers at various industry conferences.
Reader Comment
I have identified this as a root cause for damage many times over the past 30 years. 1) Never slide boards across any surface. 2) Consider using temporary standoffs 3) The last few years I have used 3d Printed holders to keep boards off surfaces. Use ESD safe PETG.
Alan Woodford, Zentech Mfg LLC
Both hard and soft surfaces present their own issues, including the ability to keep one clean versus the other. The soft surfaces must be smooth, with no bumps or ridges, and the hard surfaces must also be smooth, without any grooves or burrs. But the key here is not the surfaces themselves but the METHODS OF HANDLING THE ASSEMBLY on any given surface. Handling procedures shall be well-documented and require yearly retraining along with a quiz, and should include how to remove the assembly from its packaging and PLACING it on the mat or hard ESD surface, and never allowing it to slide out of an ESD bag or container onto the bench. Assemblies shall never be slid or pushed around on the mat or hard surface during assembly or soldering or any other processing, they SHALL be picked up and carefully turned over and put back down. This document should also spell out how many assemblies can be hand-carried, using only a two-handed carrying method, whether a cart with protective sides should be used when moving assemblies from one room to another, how many assemblies can be stacked on a shelf, provided they are in a Faraday cage (wash basket) or ESD-safe box or whatever container you wish to use, never allowing any assemblies to be stacked above the protective sides of the shelves or carts, use only an ESD-safe cart, plug yourself and the cart into the ESD jacks prior to opening and removing ESD-sensitive product, and so on and so forth. If you do not have such a documented handling procedure, you are using prehistoric methods to move your expensive products! There are no IPC or other standards that cover this because of the great variation of different companies, their personal product needs, and so on and so forth. Therefore it is up to you AND your Quality team to determine what is needed for safe handling in your manufacturing area, and make sure that gets put into place, and audit for compliance on a very regular basis.
Advanced Engineer/Scientist General Dynamics Richard D. Stadem is an advanced engineer/scientist for General Dynamics and is also a consulting engineer for other companies. He has 38 years of engineering experience having worked for Honeywell, ADC, Pemstar (now Benchmark), Analog Technologies, and General Dynamics.
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