In the processing and production of PCBA patches, some chip components cannot be processed according to conventional solder paste welding. If such components are only processed by PCBA solder paste welding, it may affect Processing quality or PCBA quality and service life. This process is the dispensing process.
In actual processing, the dispenser is usually divided into manual and automatic, which are used in small batch proofing and large batch PCBA processing, respectively.
The dispensing method of the dispenser is mainly changed according to the dispensing head. According to the dispensing pump of the dispensing head, the dispensing method can be divided into time pressure type, screw pump type, linear positive phase displacement pump type, spray Several different methods such as pump type. The following is a brief introduction to these different dispensing methods.
1. Time pressure
In many people's minds, the air pressure pump has always been the most direct method of spot coating in PCBA patch processing. It uses a compressor to produce a controlled pulsed air flow based on the principle of time and pressure. The longer the action time of the air pulse during operation, the greater the proportion of the coating material pushed out from the needle.
2. Screw pump type
The screw pump type dispensing head is highly flexible and suitable for dispensing various PCBA patch adhesives. It is not sensitive to the air mixed in the patch adhesive, but it is sensitive to the change of viscosity. The dispensing speed also has an effect on the consistency of dispensing.
3. Linear positive phase displacement
The linear positive phase displacement dispensing head has good consistency to the glue point when it is applied at high speed. It can dispense large glue points but is complicated to clean, and is sensitive to the air in the patch glue.
4. Jet pump type
The jet pump type is a non-contact dispensing head. The dispensing speed is fast, and it is not sensitive to the warpage and height changes of the PCBA substrate. However, the large glue point speed is relatively slow, requiring several sprays and complicated cleaning.
