Due to environmental factors and usage conditions, PCB boards may suffer from certain losses and aging. The shelf life of PCB boards depends on multiple factors, including material properties, usage conditions, quality and manufacturing processes, as well as maintenance and upkeep.
Based on the material characteristics of the PCB board, it can be preliminarily estimated that its shelf life is around 5 to 10 years. By reasonable design, manufacturing, and maintenance, the service life of PCB boards can be extended, and the reliability and stability of electronic devices can be improved.
What are the hazards of using expired PCB circuit boards?
1. Expired PCBs may cause oxidation of surface solder pads
The antioxidant effect of different surface treatments on circuit boards may vary, and ENIG requires that they be used up within 12 months; OSP requires it to be used up within six months.
2. The bonding ability of expired PCBs may degrade and deteriorate
After the production of circuit boards, the bonding ability between layers will gradually degrade or even deteriorate over time. When subjected to high temperatures in the reflow oven, it may cause delamination and surface bubbles on the circuit board, seriously affecting its reliability.
3. Expired PCBs may absorb moisture and cause board explosions
When the circuit board absorbs moisture and undergoes reflow, it may cause problems such as popcorn effect, board bursting, or delamination. Although this problem can be solved by baking, baking may cause other quality issues.
How to extend the shelf life of PCB?
PCB assembly can effectively extend the shelf life of PCBs. When manufacturers deliver PCBs to their respective customers, an important thing to do is to perform IQC on PCB assembly. However, in some cases, if there are problems with PCB assembly or if the manufacturer delays assembly for some reason, it is recommended to fix the PCB in a small package. For this reason, vacuum packaging has been proven to be convenient as they can prevent moisture from infiltrating the PCB and causing it to gradually deteriorate. We cannot forget that PCBA storage is an important factor in the health of industrial PCBs. Therefore, in order to extend the shelf life of PCBs, we need to avoid improper handling of PCBs from all aspects. In addition, protecting them from the effects of excessively humid weather conditions can also be helpful in this regard.
What is the handling method after expiration?
After the PCB expires and exceeds its shelf life, it must be baked first before SMT can be passed through the reflow oven. The main purpose of PCB baking is to remove moisture and moisture, to remove the water vapor inside or absorbed from the outside of the PCB, as some materials used in the PCB itself are prone to forming water molecules. In addition, after being produced and placed for a period of time, PCBs also have the opportunity to absorb moisture from the environment, and water is one of the main culprits causing PCB popping or delamination. When water vapor cannot escape from the PCB in a timely manner, there is a high chance of swelling the PCB, causing phenomena such as bubbling, expansion, and board bursting.
Considering the differences in PCBA production process and storage conditions, pre drying should be carried out before PCB (recommended within 24 hours) use. For chemically impregnated tin or silver products, it is recommended to unpack within 12 hours and repackage them.
If it exceeds the effective shelf life, it can be dried after trial use: some properties need to be retested, and if necessary, they can still be used after inspection.
For PCB boards, they are usually stored for more than 3 months before being placed on the machine to avoid the risk of moisture. It is recommended to bake them at 105 ± 5 ℃ (generally not exceeding 125 ℃) for 2 hours. Because the boiling point of water is 100 ℃, once it exceeds its boiling point, water will turn into water vapor. There are not too many water molecules inside the PCB, so it does not require too high a temperature to increase its gasification rate.
Undoubtedly, the shelf life of PCB is an important factor for the health and improvement of circuit boards. In order to enable them to perform well in our consumer electronics products.
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