What are the requirements for SMT processing?
With the development of electronic products in the direction of miniaturization, the size of components is getting smaller and smaller, and the requirements of components on the processing environment are also becoming higher, which puts forward higher requirements for SMT processing. As a SMT factory with efficient operation and good quality control, in addition to strictly controlling the process, it is also necessary to strictly control the environment of the SMT workshop and clearly understand some precautions.
1. Environmental requirements of SMT PCB assembly workshop
SMT production equipment is a high-precision mechatronics equipment. The equipment and process materials have certain requirements on the cleanliness, humidity and temperature of the environment. In order to ensure the normal operation of the equipment, reduce environmental damage to components and improve quality, The SMT workshop environment has the following requirements:
1. Power
Generally, single-phase AC220 (220±10%, 0/60Hz), three-phase AC380 (380±10%, 50/60Hz) are required, and the power of the power supply should be more than double the power consumption.
2. Exhaust
Exhaust fans are required for reflow and wave soldering equipment. For full hot blast furnaces, the minimum flow rate in the exhaust duct is 500 cubic feet per minute (14.15m3/min).
3. Temperature and humidity
The best ambient temperature in the production workshop is 23±3°C, generally 17~28°C, and the relative humidity is 45%~70%RH. According to the size of the workshop, a suitable temperature and humidity meter is set up for regular monitoring, and it is equipped with temperature adjustment. Humidity facility.
4. Air source
The pressure of the air source is configured according to the requirements of the equipment. The air source of the factory can be used, or an oil-free compressed air machine can be configured separately. The general pressure is greater than 7kg/cm2. Clean and dry purified air is required, so the compressed air needs to be de-oiled, Dust removal, water removal treatment. Use stainless steel or pressure-resistant plastic pipes as air pipes.
5. Anti-static
Workers need to wear anti-static clothing, shoes, and anti-static wristbands to enter the workshop. The anti-static work area should be equipped with anti-static floors, anti-static seat pads, anti-static packaging bags, turnover boxes, PCB racks, etc.
2. SMT PCB assembly processing tips
1. Solder paste refrigeration
The solder paste has just been bought. If it is not used immediately, it needs to be refrigerated in the refrigerator. The temperature is preferably between 5°C and 10°C, not lower than 0°C. There are many explanations on the Internet about the stirring and use of solder paste. Not much introduction here.
2. Replace the consumable parts of the placement machine in time
In the placement process, due to the aging of the placement machine equipment and the damage of the suction nozzle and feeder, it is easy to cause the placement machine to be skewed, resulting in the occurrence of high material throwing, reducing production efficiency and increasing production costs. In the case of machine equipment, it is necessary to carefully check whether the suction nozzle is blocked or damaged, and whether the feeder is in good condition.
3. Measuring furnace temperature
The quality of PCB assembly soldering has a lot to do with the reasonable setting of process parameters for reflow soldering. Generally speaking, two furnace temperature tests are required a day, and at least once a day to continuously improve the temperature curve , Set the temperature curve that best fits the welding product. Do not miss this link for the sake of production efficiency and cost saving.
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