Tuesday, 24 September 2013

What are tin whiskers and why are they a problem?

A lot has been talked about the problem of tin-whiskering and the way it could lead to problems in different electronic components. This could especially lead to big problems if the electronic components are deployed in high reliability environments such as avionics, and harsh environments such as oil rigs deployed deep sea; where failure is not an option.

But what are Tin Whiskers?
Tin whiskers are electrically conductive, crystalline structures of tin that sometimes grow from surfaces where tin (especially electroplated tin) is used as a final finish.

Reasons why Tin whisker mitigation is required.

What are the mechanisms by which Tin Whiskers form?
The mechanisms by which tin whiskers grow has been studied for many years. But unfortunately no single, widely accepted explanation of this mechanism has been established. But there are certain agreed factors in tin whisker formation. Tin whisker growth is primarily attributed to stresses in tin plating; the stresses may be from various sources which include :
  • Residual stresses in the tin resulting from the plating process.
  • Electro deposited finishes are considered most susceptible due to stresses built into the finish as a result of the plating process.
  • Formation of intermetallic compounds especially within the tin grain boundaries.
  • Compressive stresses such as those introduced by torquing of a nut or a screw.
  • Bending or stretching of the surface after plating
  • Scratches or nicks in the plating introduced by handling.
What are the commonly reported characteristics of Tin Whiskers?

The vast disparity in the observations reported by different experimenters is evidence of the complications associated with understanding and controlling tin whiskers. The following provide a very basic overview of some of the observed characteristics of tin whiskers.

Whiskers may be straight, kinked, hooked, or forked. Their outer surfaces are often grooved. Some growths may form as nodules or pyramidal structures.

Automated Re-Tinning is the solution.

All of the above characteristics have been known to cause problems, for example causing a short circuit in a satellite leading to blacking out of several important services. Therefore it is very important to understand tin whiskers and work on a solution that leads to tin whisker mitigation. A solution that has worked for mitigation for tin whiskers is re-tinning of components.

E   - info@retronix.com, sales@retronix.com

Tuesday, 3 September 2013

Failed PCB's - What happens to the electronic components mounted on them?

It is a fact that there will always be a certain number of failures when PCB's are manufactured and this is normal due to the nature of manufacturing processes. Typical causes that can cause failures are:

1) Paste issues
2) Raw PCB faults
3) Rogue Solder joints

These faults mentioned above are the first indicator that the components mounted on these PCB's may be good, since they have nothing to do with the faults. Therefore in all probability the ICs may be brand new, unused and in perfect working order.

But sometimes company policy states that these failed PCB's be send straight to landfill and recycled, this leaves a lot of potential threats, as certain people with vested interests may get the opportunity to counterfeit these components by using the scrap material from these landfills, also in some cases be sold faulty or completely degraded to unsuspecting customers who buy and implement them in their supply chain leading to  huge problems later to deal with.

  Picture used for representation purposes only
Companies were taking this risk of sending the failed PCBs straight to landfill since there was no safe way of recovering these perfectly good components from PCBs for re-use. However recently there is a process developed that can recover these components for re-use in a very safe manner and without reflow cycles, and this is certainly a much better and economical way to recycle them than to throw the full unit away.

When new components are scarce, as is often the case, their recovery becomes even more important and even more profitable. The risk of dealing in counterfeit components has increased with the 2012 US National Defence Authorization Act. As this global issue becomes more and more of a problem, the ramifications, sentences and fines are becoming increasingly severe. Therefore the best option is to recover this ICs in a safe manner for re-use.

Here is a small demonstration of the process :


By recovering electronic components, up to 50 times the value can be realised from the scrap. The treated scrap, with components removed, could then be sent to any recycler, thereby also eliminating counterfeiting and the re-circulation of faulty and degraded parts.

E   - info@retronix.com, sales@retronix.com