What is PCBA (PCB Assembly)?
PCBA is the abbreviation of PCB assembly, a printed circuit board with various components soldered on the surface.
The PCBA processing process will go through several storage stages: after the SMT processing before transferring to the DIP stage; after the PCBA test is completed and the finished product is assembled, there is a period of storage time.
With the development of science and technology, people are paying more and more attention to the use time of PCBA circuit boards and the reliability of high-frequency operation. More and more attention is paid to the shelf life of PCBA. After the final processing of the PCBA is completed, if the finished product is not assembled in time, the PCBA needs to be stored to prevent the PCBA from being exposed to the air for a long time, which affects the performance and reliability of the PCBA.
Under standard storage conditions, the storage time limit of PCBA is 2~10 years.
What are the main factors that affect the preservation cycle of PCBA?
Below we will introduce the PCBA storage environment and requirements in detail.
1. Storage environment
A humid and dusty environment is not conducive to PCBA preservation. These factors will accelerate the oxidation and dirt of the circuit board and shorten the storage period. It is generally recommended to store in a dry, dust-free space with a constant temperature of 25 degrees Celsius.
For PCBA boards that have not been used for a long time, conformal paint should be applied. The three-proof paint has the functions of moisture-proof, dust-proof, and oxidation-proof, which can effectively extend the PCBA storage time. The storage time of PCBA can be extended by nine months after coating the conformal paint.
2. Reliability of components
The reliability of different components also largely determines the shelf life of PCBA. High-quality materials and SMT process components can withstand harsh environments, with a broader range of capabilities and stronger oxidation resistance, which also provides a guarantee for the stability of PCBA.
3. The material and surface finish process of the printed circuit board
The material of the printed circuit board itself is improbable to be affected by the environment, but its surface finish process is greatly affected by air oxidation. A good surface finish process can extend the shelf life of PCBA.
| Surface Finish | Storage environment | Storage duration |
| HASL | 1. Temperature: 22±4℃ 2. Humidity: 30%-60%RH 3. Vacuum packaging (containing desiccant). | 12 months |
| Immersion Gold | 1. Temperature: 22±4℃ 2. Humidity: 30%-60%RH 3. Vacuum packaging (containing desiccant). | 6 months |
| Immersion Tin | 1. Temperature: 22±4℃ 2. Humidity: 30%-60%RH 3. Vacuum packaging (containing desiccant). | 3 months |
| Immersion Silver | 1. Temperature: 22±4℃ 2. Humidity: 30%-60%RH 3. Vacuum packaging (containing desiccant). | 3 months |
| OSP | 1. Temperature: 22±4℃ 2. Humidity: 30%-60%RH 3. Vacuum packaging (containing desiccant). | 3 months |
4. Packing method
PCBA should not be in contact with air and water when stored. First, use a vacuum bag to pack the PCBA board, and a bubble film needs to be surrounded by the box when packing. The bubble film has better water absorption, which plays a good role in moisture prevention. Of course, moisture-proof beads and drying The agent is also indispensable. After sealing, the box must be stored in a dry and ventilated place with partition walls and off the ground and avoid sunlight.
5. Operating load
The PCBA operating load is the most critical factor in its shelf life. The high frequency and high load itself will have a continuous high impact on the circuit board circuits and components. PCB boards and electronic components are more susceptible to oxidation due to heat, and it will be causing short circuits and open circuits during long-term operation. Therefore, the operating parameters of the PCBA board should preferably be in the middle-value range of the components and avoid near the peak value, which can effectively protect the PCBA and extend its shelf life.
6. Control the temperature and humidity of the warehouse
The temperature of the warehouse where PCBA is stored is best controlled at 23±3℃, 55±10%RH. An excellent PCBA storage environment has a temperature of fewer than 25 degrees, relative humidity of less than 65%, temperature control, and no corrosive gas in the indoor environment.
For the PCB with OSP surface finish, more stringent storage conditions are required for PCBA storage due to its thin protective film.
How to extend the storage time of PCBA?
1. Good storage environment: temperature is less than 25 degrees, relative humidity is less than 65%, with temperature control, no corrosive gas in the indoor environment.
2. General storage conditions: the temperature is not higher than 35 degrees, the relative humidity is less than 75%, and the indoor environment is free of corrosive gas.
3. The temperature of the PCBA warehouse should be controlled at 23±3℃, 55±10%RH. Under such conditions, PCBA boards with surface finish such as immersion gold, electro-gold, HASL, and immersion silver plating can generally be stored for six months. PCBA boards with surface treatments such as immersion silver, immersion tin, OSP, etc., can generally be stored for three months.
The storage period of PCBA is a comprehensive work, which needs to follow scientific design specifications, production process specifications, and operation specifications so that its storage period can be extended to the greatest extent.
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