The printed circuit board (PCB) is designed to connect electronic components that are etched in copper layers laminated together. In general, PCBs are the heart of every electronic that surrounds us! But how long do they last? Is there anything that manufacturers do to improve their life span? How can we make sure that the environment of our PCBs is right for an optimal and extended life?
The main factors in PCB lifetime are the type, size, and the conditions that they are operating. (voltage, temperature, etc.). On the other hand, transistors are exceptional and almost a miracle in electronics. They are unlikely to “burnout”, but there is a possibility when the transistors are constantly exposed to certain conditions to die eventually.
The heat resistance has improved significantly in the last few decades so it is early to tell the exact life span of each PCB design, but this is a good guess considering all the tests that are being performed in order to improve the durability and reliability.
In the electronic industry, there are constant changes and custom design manufacturing but the thermal and mechanical reliability of a PCB has to always remain at a high level. A lot of research, testing, and prototyping is required for the manufacturers to maintain these reliability targets when assembling a printed circuit board.
The necessary tests in order to guarantee reliability and longer life are often expensive and time-consuming. The PCBs have to be designed, produced, assembled, and eventually a detailed failure analysis process if necessary to be performed.
In the PCB industry, enhancing the design rules is one of the most targeted scopes. Everything is driven by the growing trend of miniaturization of electronics. There is a major standardized board-level drop test that is well-known and applied by the manufacturers.
The drop test or also called (BLDT) is directly related to the life of the printed circuit boards as any mechanical failures caused by events such as intense vibration, dropping, handling, and transportation can reduce significantly the lifespan of the board. We will review this method in order to acquire the information for the durability and life the PCBs are facing.
Board Level Drop Test
The BLDT test is based on testing the vehicles for solderability and terminal PTHs. In that process, all the tests and events are monitored online for verification. There is specific equipment where the PCBs are mounted with their main side (assembled side) facing down prepared for a drop test.
Nine test drops are performed! The test is immediately stopped after the first failure. Improvements are made in the design in that case and the tests are being held once again until completed. After the board has passed the test, a measurement of all tested components is made and pictures are being made for each.
You are probably starting to realize how time-consuming and difficult it is to perform this series of tests. But this is nothing compared to what’s to come!
In order to do that there is a series of follow-up engineering constants tests. The next step is a basic engineering zone model test that is made to determine and describe the fracture process in the dielectric layers. Later a finite software is used to generate a simulation model that will determine the sub modeling technique and local stress situation.
The results of the sub-model will allow the evaluation of the stress test and determination of the loading situation parameters for the most failure possibilities. In case of a crack or failure during the test, again the manufacturers proceed with innovation and updates until all the tests are complete and successful.
In case, however, of failure, there is a specific operation that is following the failure pattern and a series of observation experiments. The failed board is examined and analyzed by light microscopy. Another interesting thing is that the software that is analyzing the chances of failure is 99% accurate and its prediction is always true.
Basically whenever a model or end design is inserted in the drop test software, and the software concludes that there is a possibility of breaking under certain conditions the physical real-life test always proves it.
And finally, there are more software simulations where the lifetime prediction is taking place. There are a couple of amplitude levels and local loading simulations that are performed in order to generate statistics of failure in the various specific types.
We can conclude this test as a general idea of bringing a concept of simulation to life, testing it, improving and reducing the possibility of failure. Of Course on the market are only boards that are designed the way in which the test software is sure that they are 100% reliable. This is what the guarantee relies on, so don’t worry the PCB you are buying hasn’t been dropped 9 times.
There are still other stringent qualifications that manufacturers have in place when ensuring that the device is robust. One of them is “ High-Temperature Operating Lifetime ” (HTOL). The devices are tested in extreme temperature in order to accelerate any issues with aging and consistent work under higher temperatures.
However, the tests can briefly guarantee the 10 years of operation under circumstances outside the recommendations including safe temperatures. Speaking of aging, there is one major limitation that the manufacturers are still fighting against, and this is the metal used to connect the devices. Over time en “electromigration” can happen (the metal is physically moving), caused by the flowing through these tiny wires.
What is Bare PCB Shelf Life?
In general, after a printed circuit board is manufactured, it has a default shelf life. Whenever this shelf life is exceeded, the PCB has to be baked. If the board baking is done right there is a high potential for the delamination to be reduced but it does not restore the shelf life.
The printed circuit board developer shall mark the PCBs with a four-digit code representing a date. The code includes a two-digit “week” number that could range from 01 (the first week of the first month in the year January) to 52 (The last week in the year, December). The next two digits are the year that for example can be: 98 for the year 1998 or 05 for the year 2005.
Here is an example: 0302 is the third week in January for the year 2002. And this is how to determine the shelf life of a printed circuit board.
As a result, the board baking will destroy solderability, and the intermetallic compounds’ growth will be accelerated. In most cases, baked boards end up with an exposed intermetallic layer that no longer has solderability. This is why the coating durability is essential here, and the reasons why manufacturers are following a variety of requirements when developing printed circuit boards design.
Many people are wondering how often can a board be baked? And there is no specific answer here. Many boards have to be baked during the assembly process, so this is the point in time for that operation.
The continuous baking of the boards is not recommended as the ability of the laminate material to absorb the moisture is very high. It is extremely important for the boards to be soldered immediately after the baking process. This way the laminate material will absorb all the moisture that is removed during the baking cycle in the following 7-11 hours.
So now we have a better understanding of the PCB's life and what the manufacturers are doing to prevent failures. Now let’s take a look at some common causes for failure modes.
Printed Circuit Board Failures
As the core of all electronics, the printed circuit boards are of course vulnerable mostly to wreak havoc, causing an immediate power failure. We will now review some of the common failures found in the PCBs.
- Poorly Manufactured Components
Even though the manufacturers are following all these tests and experiments to guarantee a long and healthy lifespan, there is a possibility of acquiring a poorly manufactured PCB. In that case, some of the components could have symptoms including connection issues, lack of solderability, and even leftover flux . It is a substance that is mainly used to aid during the soldering process and it can harm your components as it causes corrosion on the printed boards.
- Environment Factors
The common problem here is temperature. It can cause a malfunction in the printed circuit board. This problem can be observed mainly in Spa and Pool equipment due to the high electrical currents. With that kind of extreme temperature change, a curving or wrapping is possible, which on its own can damage the soldering joints. In wet environments, moisture is another threat due to the location that may allow water to enter, causing oxidations, rusting, and corrosion.
Another environmental issue is the problem of building up dust, dirt, and even living or dead insects. It is happening mainly on technology such as computers, laptops if they are not cleaned for long periods of time, eventually causing an overheat.
- Burnt Pieces
This one is a well-known and common issue. Sometimes PCBs components burn due to the consistent work under higher temperatures than recommended. Dust as we already mentioned can lead to overheating. Each of the components has its own amount of heat that it can absorb, which depends on the structure and size.
And of course, we have aged as one of the known limitations that the manufacturers are still fighting against. For example, a failed capacitor will 100% guarantee immediate power issues. The same goes for almost all the components in the printed circuit boards. But you can always replace the old parts with the new ones so there is no need to worry.
Have in mind that there is always a concern of high pricing for a brand new circuit board. However, more of the PCB issues can be resolved for a price that is not nearly the manufactured price and it is completely affordable.
There are a few issues that we already mentioned that do not require a general inspection and can be fixed fast and easy. On the other hand, there are deep-rooted general issues where diagnosis by a trained technician is necessary. But a repair is almost always your better alternative.
We now know that the manufacturers are doing their job for the high prices that PCB designing goes for. However, we also know that sometimes there are exceptions, which are extremely rare occasions. The only thing that you need to do is carefully choose a manufacturer that can design a PCB as per your requirements and there is nothing to worry about. We wish you good luck with your printed board purchase in the future!