To My Readers



If this is the first time you're visiting my blog, thank you. Whether you're interested or just curious to find out about PCB reverse engineering (PCB-RE), I hope you'll find something useful here.

This blog contains many snippets of the content in my books to provide a more detailed overall sampling for my would-be readers to be better informed before making the purchase. Of course, the book contains more photos and nice illustrations, as evidence from its cover page. Hopefully, this online trailer version will whet your appetite enough to want to get a copy for yourself.

Top Review

I started doing component level repair of electronics with (and without) schematics more than 40 years ago, which activity often involves reverse-engineering of printed circuit boards. Although over the years my technical interests have shifted into particle beam instrumentation, electron microscopy, and focused ion beam technology fields, till this day——and more often than not——PCB repairs have returned multiple multi-million-dollar accelerators, FIB, and SEM instruments back to operation, delivering great satisfaction and some profit.

Many of the methods described by Keng Tiong in great details are similar to the approaches I've developed, but some of the techniques are different, and as effective and useful as efficient and practical. Systematic approach and collection of useful information presented in his books are not only invaluable for a novice approaching PCB-level reverse engineering, but also very interesting reading and hands-on reference for professionals.

Focus on reverse engineering instead of original design provides unique perspective into workings of electronics, and in my opinion books by Keng Tiong (I've got all three of them) are must-read for anybody trying to develop good understanding of electronics——together with writings by Paul Horowitz and Winfield Hill, Phil Hobbs, Jim Williams, Bob Pease, Howard Johnson and Martin Graham, Sam Goldwasser, and other world's top electronics experts.

Valery Ray
Particle Beam Systems Technologist

Monday, March 27, 2017

Conformal Coatings

As the term implies, a conformal coating is a thin film (25-75μm) of protective chemical substance (or membrane) that coats over a PCB or electronic assembly by conforming to its contours and components. Conformal coating in effect applies a layer of insulation on the PCB against moisture, dust, heat, fungus, and corrosion, etc.

Not all PCBs are conformal coated—motherboards found on personal computers and laptops usually aren't, including circuit boards that are installed in most mobile phones. In fact, many PCBs found in commercial household products like TV, washing machines, fridges, and hi-fi sound systems seldom are, except in countries where the weather and environment warrant its use. Military circuit boards and PCBs used in aeronautical designs, on the other hand, because of the harsh and often extreme conditions in which they operate in, must of necessity be conformal coated to ensure they continue to be functional and reliable.

PCBs that are conformal coated usually have a glossy shine on both the component and solder sides, and will exhibit a luminous blue glow when placed under ultraviolet (UV) lighting. The table below lists five types of material you will most probably encounter:


Most conformal coated PCBs I worked on so far use some form of acrylic resin as the medium, which is quite easily removed with solvents like the Humiseal 1080, a VOC-compliant, non-ozone depleting
chemical.

There are rare instances where the coating is epoxy or polyurethane, in which case I resorted to running a fine-pitch file gently over the tips of the component legs to lightly scrap off the coating to expose the conductive solder, and then brushing off the flakes using an anti-static brush.
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