Arrgghh! Parts without Numbers!
By: Clive, Max
Tags: Hardware, Electronics, Manufacturing, Inspection, Pcb

As you may recall, I recently penned a column, What’s it Mean? Taiwan’s Yageo to buy USA’s Kemet! Between them, Yageo and Kemet create a wide variety of discrete components, including resistors, capacitors (e.g., tantalum, aluminum, multilayer ceramic, film, paper, polymer electrolytic, supercapacitors), AC line filters, EMI cores and filters, flex suppressors, electro-mechanical devices (relays), metal composite inductors, ferrite products, and transformers/magnetics.

If the SMT resistors on your PCBs have no markings, it makes inspection all the more problematical (Image source: Withheld by request of the image owner)

The reason I mention this here is that I just received an email from a friend who we’ll call Kermit. Kermit works at a company we’ll call Hoppier Enterprises (he doesn’t want me to mention his real name or company in fear of reprisals). In his email, Kermit spake as follows:

Hi Max, do you remember writing a column several years ago about the folks at Yageo deciding to stop putting markings on their SMD resistors? Ultimately there was a public outcry and they reversed their decision. Well, I just got word that Vishay has stopped putting markings on their resistors. We recently received several hundred PCB’s with unmarked resistors on them so we can’t fully inspect them. Have you heard anything about this? Is this becoming a trend that we will just have to live with? How are other companies doing quality control (QC) on their PCBs?

I remember that column: Beginning of the End for SMT Component Markings? As I recall, there was quite an outcry at the time (circa 2013 to 2014), not the least of which is that Yageo kept the same part numbers — they simply stopped putting marks on the parts. As Kermit says, there was something of a public outcry about this, and Yageo eventually reversed their decision.

Unfortunately, it looks like we have a game of Whac-A-Mole on our hands, because the folks at Vishay have indeed popped their heads up to say they’ve stopped adding resistance value markings to thick film SMD resistors, from 0603 to 2512 in size.

Even worse, the guys and gals at Vishay are following the same path as the folks at Yageo; i.e., even though they are no longer marking the components, they are keeping the same part numbers. You need a Vishay account to see the product change notice on the Vishay website, but you can access it on the Digi-Key site.

Now, it’s obvious that not having component values marked on parts would be a real pain if you are making hobby projects or one-off prototypes. However, you may think that not having component markings is less of an issue in a full-scale manufacturing and production environment in which automatic machines populate the components on the boards.

In reality, the lack of component markings makes things problematic for everyone. Imagine you’ve just taken delivery of 1,000 PCBs. Not having component markings degrades the value of even a first-pass visual inspection.

Even worse, component values may change with new revisions of the board, in which case troubleshooting bad boards becomes even more of an issue because you can no longer look at a resistor to ensure it has the desired value.

If you are involved in designing, assembling, manufacturing, or distributing boards — and if you purchase your parts from Vishay — I think this would be a really good time to make your feelings on this topic heard. If we cannot persuade Vishay to reverse their decision, then it probably won’t be long before other vendors like Yageo and Kemet (as was) follow suit.

What say you? Do you think this is a problem, or don’t you care one way or the other?