PCBA Tech - PCBA cleaning steps and test description

After PCBA has been used for a period of time, it needs to be cleaned, because each product has a different level and the cleaning process is also different, and each device has its own cleaning plan. After purchasing PCBA, you need to test the product to see if it is aging. This kind of test is necessary. Let's take a closer look at "PCBA cleaning steps and test descriptions".

[PCBA cleaning steps]

Brief introduction of several advanced PCBA cleaning processes At present, many PCBA production and manufacturing use cleaning processes. For products with different levels of requirements, the fluxes used, and the differences in the processes, the cleaning agents that need to be used, the required equipment, The crafts are all different. Most of the equipment supply has introduced the cleaning machine equipment and its cleaning program, and firstly detects and analyzes the residues after welding in the manufacturing plant, and then provides a targeted system cleaning solution.

There are fully automated online cleaning machines, semi-automated offline cleaning machines, manual cleaning machines, etc., suitable for all water-based (cleaning with ionized water), semi-aqueous (cleaning with aqueous chemical substances, such as saponification liquid) and All chemical solvent cleaning. Many companies tend to adopt water-based cleaning agents and develop in an environmentally friendly direction.

1. Fully automated online cleaning machine

A fully automated online cleaning machine, which is thoroughly effective against organic and inorganic contaminants such as rosin flux, water-soluble flux, no-clean flux/solder paste, etc. on the surface after SMT/THT PCBA soldering Of cleaning. It is suitable for large-scale PCBA cleaning. It uses safe and automated cleaning equipment to be placed on the Denso production line, and completes the chemical cleaning (or water-based cleaning), water-based rinsing, and drying processes online through different cavities.

During the cleaning process, PCBA is cleaned in different solvents through the conveyor belt of the cleaning machine. The cleaning fluid must be compatible with components, PCB surface, metal coating, aluminum coating, labels, writing and other materials. Special parts need to consider whether they can withstand cleaning.

The cleaning process is: board loading - chemical pre-washing - chemical cleaning - chemical isolation - pre-rinsing - rinsing - spraying - air cutting drying - drying

2. Semi-automated offline cleaning machine

A semi-automated off-line type, the cleaning machine thoroughly and effectively cleans the residual rosin flux, water-soluble flux, no-clean flux/solder paste and other organic and inorganic contaminants on the surface after SMT/THT PCBA soldering. . It is suitable for small batch and multi-variety PCBA cleaning. It can be set anywhere on the production line through manual handling. It can complete chemical cleaning (or water-based cleaning), water-based rinsing, and drying in a cavity offline.

During the cleaning process, PCBA usually needs to be fixed by a fixture or placed in a basket. The cleaning solution must be compatible with components, PCB surface, metal coating, aluminum coating, labels, writing and other materials. Special parts need to be considered whether they can withstand Clean.

The placement density and placement angle of PCBA in the cleaning basket have certain requirements, and these two factors have a direct impact on the cleaning effect.

3. Manual cleaning machine

A manual cleaning machine (also called constant temperature cleaning tank), which is aimed at the residual rosin flux, water-soluble flux, rosin flux, no-clean flux/solder paste, etc. on the surface of SMT/THT PCBA after soldering., Inorganic pollutants are thoroughly and effectively cleaned. It is suitable for the cleaning of small batch samples of PCBA. Through temperature control, it is adapted to the manual cleaning process of MPC micro-phase cleaning agent and completes the chemical cleaning in a constant temperature bath.

Note: Ultrasonic cleaning, as a low-investment and easy-to-implement solution, is also adopted by some PCBA manufacturers. However, the aerospace military industry limited (prohibited) the use of ultrasonic cleaning technology. Ultrasonic cleaning should not be used to clean electrical or electronic parts, components or parts equipped with electronic components. Protective measures should be taken during cleaning to prevent damage to the components (US military Standard DOD-STD-2000-4A "General Welding Technical Requirements for Electrical and Electronic Equipment");

The IPC-A-610E-2010 Level 3 standard also generally prohibits ultrasonic cleaning processes.

[PCBA test description]

There is such a problem. We often find in PCBA processing that the various functional indicators of the PCBA board are normal at the time of shipment, but after a short period of use, customers will find that various undesirable situations will occur. Investigate the reasons and find out, so In fact, it is necessary to carry out the aging test of PCBA processing products.

The aging test generally simulates the external environment to test the finished PCBA, so that the functional board is subjected to the change of air temperature in a thermal aging equipment with temperature changes, and the function is exposed through the combination of high temperature, low temperature, high and low temperature changes and electric power. Defects of the board, such as poor welding, component parameter mismatch, temperature drift and faults caused during the debugging process, can be eliminated in order to stabilize the parameters of the non-defective functional board.

Now when PCBA processing plants are performing PCBA processing, it is necessary to conduct aging tests according to customer needs or the characteristics of PCBA processed products. So what should be done?

There are 3 standards for PCBA burn-in test. According to these 3 standards, general problems can be found.

1 Low temperature work: After placing the control board at a temperature of -10±3°C for 1h, under this condition, it should be loaded with rated load. Under the conditions of 187V and 253V, power on and run all programs, and the program should be correct.

2 High temperature work: After putting the control board at 80±3 degree Celsius/h, under this condition, with load, under the conditions of 187V and 253V, power on and run all the programs. The program should be correct.

3 High-temperature and high-humidity work: Put the control panel on the temperature 65±3 degree Celsius and humidity 90-95% for 48h, electrify and run the programs with the rated load, and the programs should be correct.

The specific method of aging is to put the functional board at the ambient temperature into the heat aging equipment at the same temperature. PCBA processed products are in operation. Then the temperature in the equipment should be reduced to the specified temperature value at a specified rate. When the temperature in the equipment is stable, PCB processed products should be exposed to low temperature conditions for 2h.

The temperature inside the equipment should then rise to the specified temperature at a specified rate. When the temperature in the equipment is stable, PCB processed products should be exposed to high temperature conditions for 2 hours. The temperature inside the equipment should then be reduced to room temperature at a prescribed rate. Continue to repeat until the specified aging time, and perform a measurement and record of the PCBA processed products according to the specified aging time.