Tin Whiskers in a Wireless Thermostat Receiver

Introduction

Tin Whiskers are a crystalline growth made of the element tin. They are in the form of a very thin straight hair with one end attached to the tin from which they are formed.

They often form on lead free solder used to fix components to circuit boards now that lead is banned.

The Tin Whiskers I Found

In my case they have grown on a piece of tin plated steel used to screen electronic components which are part of a central heating wireless thermostat radio receiver. This receiver has developed an intermittent problem and doesn’t switch on my central heating when it should.

I suspect a tin whisker growing inside the component screening can is the cause of the electrical fault, and over time it grew large enough to touch some electrical connection and make a short circuit.

Since I have not completely dismantled the item to find out for sure I don’t know if that is correct. However as you can see from the pictures below, the Tin Whiskers that I have found on the outside of the screening can are up to 2mm long. Although I already knew of their existence these are the first I have seen in 50 years of handling electrical or electronic devices.

I have used a USB microscope connected to my computer to photograph them, but I have had a lot of difficulty. They are so thin they are hardly visible with a watchmakers eyeglass with 10x magnification.

the largest tin whisker 2mm long
The largest Tin Whisker I have found is 2mm long.
more tin whiskers
More Tin Whiskers

The tin plate shown here is covered in minor scratches which I think has opened the surface to their formation. There are many small but visible stumps along these scratches which seem to be the beginning of whiskers. See below:

tin whiskers growing on a tin-plate screening can
Tin Whiskers growing all over a tin-plate screening can.

References:

Author: Helpful Colin

I have a background in telecommunications and a fascination with all things scientific and technical - from physics to electronics, and computing to DIY.

2 thoughts on “Tin Whiskers in a Wireless Thermostat Receiver”

  1. That’s why I don’t like lead-free electronics. I expect manufacturers may not be too upset at the shortened life of consumer electronics, necessitating replacement, but in safety-critical equipment I think it should be banned.

    1. I see lead free solder as being the cause of many problems. It amounts to built in obsolescence. Tin whiskers could cause the worst type of faults and the most costly and difficult to fix. The item I had to replace cost around £90 and failed after about 6 or 7 years.
      I still have nearly full reels of 0.7mm and 1.2mm 60/40 solder fortunately, and it might still be possible to get it from R. F. Potts.

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