Shelf life has always been complicated when it comes to electronic components. Back when different materials were used “solderability” was a great concern and shelf life was more common on datasheets. However, in modern times, you hardly see the information stated in datasheets anymore (this depends on the manufacturer, but it is far less common across most manufacturers based on the number of questions we get on shelf life).
Why Did it Used to Be More Common?
Before the 1980s, parts didn’t have newer materials, which caused solderability problems. Different materials were discovered to reduce corrosion or “whiskering” due to components having tin contacts with no protection: https://nepp.nasa.gov/whisker/ (here is good governmental documentation of what used to be common on older electronic parts). Whiskering can cause a variety of problems in components like shorts or cause soldering issues.
What Has Been Done to Increase Shelf Life?
You do see tin as a common material, but chemical and/or material engineers found other alloys and materials to reduce this problem. Some components can have indefinite shelf lives since they will most likely surpass average human life spans, typically these components will only be replaced at the time they look to be “spent” or current behavior is no longer meeting specifications when used.
Is There a General Consensus on Average Shelf Life?
There actually is a general “rule of thumb” for most components. For a long time, the average time has been two years from purchase. However, since there have been advancements, many components behave just as well after four years compared to the two-year threshold. Texas Instruments completed a study about this and concluded that standard moisture barrier storage would protect up to thirty-two months. “Long Term” storage could be valid up to five years, however, they found no impact on MSL performance or solderability on product stored for two to seventeen years when compared to product that had been recently manufactured. Here is a link to the study: https://www.ti.com/lit/wp/slva304/slva304.pdf
Is Date-Code Tied to Shelf Life?
Date-Code is a traceability piece of information for when a component was created. Customers tend to believe that newer product has more potential to be improved. They also believe that a new product is less susceptible to issues seen in transportation and handling. A final belief that seems common is that an older part has more potential to see more ownership transfers and potentially lose uninterrupted traceability to the original manufacturer. In this case, it’s less about shelf-life and more about if a product becomes obsolete.
What Components are Most Affected?
Discrete parts like transistors, LEDs, resistors, capacitors, and other similar parts are susceptible to aging via corrosion and “whiskering”, but not as much as integrated circuits. Discrete parts will have a very long shelf life. Integrated circuits are far more susceptible to whiskering and corrosion. There are specific components where shelf life must be stated: thermal pads, certain adhesives, batteries, certain chemicals. Anything chemical in nature in the electronics world will degrade in quality over time, (usually faster than a typical component). Here are some other related posts.
- Ceramic Capacitor Aging: Some chip capacitors, particularly those 1µF or higher, do experience aging that can cause the capacitance value to be out of tolerance upon receipt, or after storage, but are still perfectly viable.
- Shelf Life of Bourns Resistors: Some resistor manufacturers do include shelf-life in datasheets. It is generally recommended that you do a sample solderability test on a product that was stored for at least two years.
What Should I Do if Components Are Corroded or Have Whiskers?
The suggestion is to try to use some electronic cleaner on these items or even rub regular printer paper on leads to remove the corrosion layer. Here is a good YouTube video showing this:
Most components like ICs and discrete products can be washed before soldering (most switches cannot unless they have a proper IP rating).
How Do I Prevent This?
There are recommended storage temperatures usually mentioned in the datasheets. It’s always a good idea to have most parts stored in a low humidity environment regardless of MSL. The presence of more water in the air allows more corrosion to occur. Tin whiskers are tied to the manufacturing process and material but can be cleaned (see this NASA article for more in-depth information on tin whiskers: Basic Info on Tin Whiskers. ) If you are storing PCBs, vacuum sealing is recommended. You may even use desiccant for components and PCBs to reduce moisture. The best-case scenario is to solder the part before that two to four-year recommendation. The final note would be to check your product before soldering for any degradation on terminals.