A hobby of mine is to take apart discarded electronics -- to see what I can learn. Sometimes, I'm just puzzled.

I've seen this style in name-brand stuff, meaning high quantity, like radios and vcr's. This PCB was I believe removed from an old tv having mini fluorescent tube backlighting, I sure would like to know what to call this style of pcb-design, and is this something only the big guys do (is this totally custom) or is there a pcb mfg house that does this, because I've never seen it (though I admit, I didn't look too hard). I assume this style is to make design and manufacture as cheap as possible. And there's probably software that allows to design this way, though I don't know what it is.

PCB, component side, without flash: PCB, component side, without flash

PCB, component side, with flash: PCB, component side, with flash

PCB, underside, no flash PCB, underside, no flash

It also has this interesting style for MOSFET that I'm curious about (I call these horns -- what are they called?):


SMT MOSFET with solder-"horns"

And here's another (A unicorn?), with teardrop-shaped solder on the middle pin:

TO-220 with center pin having a teardrop-shaped solder-blob


Here is an asymmetrical one:

Two tear-drops, right one straight up, left one bent to the left


3 Answers 3


It's a single-sided punched paper-based phenolic PCB. Extremely cheap per square meter in high quantity compared to FR4, but some tooling costs for the dies.

The features you show are to get high yield without a lot of touch-up after wave soldering. The parts on the bottom are immersed in molten solder as the board moves through one more more "wave(s)" caused by a stirrer in a solder reservoir, subsequent to preheating and fluxing.

Those triangle patterns take up some of the solder on the trailing edge of the wave that would otherwise tend to cause shorts that would have to be manually touched up later.

  • 21
    \$\begingroup\$ Those features are sometimes called "solder thieves". \$\endgroup\$ Aug 20, 2021 at 17:52
  • 1
    \$\begingroup\$ Having not done any wave soldering, I find the TPC8214 photo interesting where one pin has significantly more solder than the other 3 pins (that are on the same side). Is that common (random) result, or is that pin special and the extra deposited solder is on purpose (due to the copper plane)? \$\endgroup\$ Aug 20, 2021 at 17:52
  • \$\begingroup\$ I think that I've noticed that the triangles all go in the same direction. Is that right? \$\endgroup\$ Aug 20, 2021 at 18:04
  • 1
    \$\begingroup\$ @ChrisKnudsen Probably the plane contributes. The thieving pads are common when SMT parts have to be mounted on the bottom. Se also this question. \$\endgroup\$ Aug 20, 2021 at 18:04
  • 2
    \$\begingroup\$ @MicroservicesOnDDD Yes, because of the direction the board goes through the solder wave. \$\endgroup\$ Aug 20, 2021 at 18:10

The comments about solder thieves (the unicorn horns) are spot on. In some cases you'll find two different boards of the same basic design with different orientation of the thieves because of the way multiple boards were panelized.

This is from the era when it was cheaper to cut and place jumpers in the board than have a double sided plated through hole design. The boards were also often punched with a huge die rather than drilled. A lot of non-recurring cost traded for lower unit cost in a high volume product.

The main thing that killed this approach was the transition to surface mounted parts. As long as you were going to wave solder a board anyway, the only cost of the jumpers was inserting them and they were incredibly cheap. The transition to SMD made the boards smaller and used cheaper parts. The jumpers would have been much more expensive that double sided or even multilayer boards in the new environment.


That board could have been laid out in any PCB CAD program. The layout person just has to put most tracks on the bottom side, and ensure that any top side tracks are short and straight.

  • 1
    \$\begingroup\$ I was looking for an automated layout solution that I imagine exists. And how do you do the triangles? \$\endgroup\$ Aug 20, 2021 at 18:02
  • \$\begingroup\$ @MicroservicesOnDDD: the triangles would be part of the component footprint. \$\endgroup\$ Aug 21, 2021 at 19:13

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.