原创 Are SMT component markings becoming obsolete?

When I was starting to get into electronics, it was the heyday of lead through-hole technology. I used to love all the colours associated with various components, such as the coloured bands on the resistors shown below.

It previously wrote: "When I'm building a circuit, if I have a selection of capacitors (for example) of the required type and the same value but of different shapes, sizes, and colours, then I will select the one that best matches, complements, or contrasts the other components on the board."

Of course, quite apart from their aesthetic qualities, the coloured bands on the resistors served to distinguish their values, tolerances, and so forth. This is particularly useful when you are a hobbyist, because you are constantly hunting for parts in your component treasure chest.

I understand that some people think it's less important in a full-scale manufacturing and production environment in which automatic machines populate the components on the boards. However, I cannot imagine a world in which lead through-hole components were all a drab grey colour without any identifying markings to distinguish one from the other. Apart from the blandness of it all, can you conceive how difficult it would be to troubleshoot such a board? All of which leads me to an email I just received from my chum, Rick Curl:

Hi Max, last month I received a bunch of circuit boards that Whitesburg Electronics assembled for me and I was surprised to see that some of the 1206 resistors had no markings on them. We have used Yageo brand resistors (that we purchase through Digi-Key) for several years and have not changed the part numbers that we order. I called Digi-Key about this. They said it was obviously a manufacturing defect and to throw any remaining parts away and they replaced our remaining stock with resistors having proper markings.

Last week I received a new shipment of resistors—about half had no markings. A little searching on the Internet turned up this troubling press release.

I spoke with the people at Digi-Key and this was news to them.

I have always wondered why most surface mount ceramic capacitors were not marked. I would gladly pay double to get capacitors with markings on them. I hope we're not about to see resistors go the same route.

Have you heard anything about other manufacturers removing the markings from surface mount resistors? It really makes it tough to do a proper visual inspection of the board. And what about Yageo's justification for this move? Environmental protection? Sounds like a smoke screen to me. Will IC's be next?

I emailed Curl to ask him about my thought that some people think it's less important to have component markings in a full-scale manufacturing and production environment in which automatic machines populate the components on the boards. He replied:

We are a small company and we have third parties assemble boards for us. Not having markings makes visual inspection very difficult. Troubleshooting bad boards becomes much more difficult because, over time, there may be component value changes, and we will no longer be able to look at a resistor to verify its value.

With regard to Yageo's justification of "environmental protection," it would be wonderful if manufacturers did such things voluntarily. If I were a more cynical man, however, I might be tempted to think this was more of a cost-cutting exercise.

The strange thing to me is that, as big as Digi-Key is and as many Yageo parts as it carries, it is hard to believe that the company was blindsided by this. The fact that it assumed the unmarked parts were defective speaks volume. It's also interesting that Yageo didn't modify the part number when it made this change. And another strange thing is that the specification sheet for these parts on Yageo's website still indicates that they are marked. If a bunch of Yageo customers expressed their concern, it might be possible to nip this in the bud. What do you think about the idea of unmarked surface mount parts?