In the processingand production of PCBA patches, some chip components cannot be processedaccording to conventional solder paste welding. If such components are only processedby PCBA solder paste welding, it may affect Processing quality or PCBA qualityand service life. This process is the dispensing process.

In actualprocessing, the dispenser is usually divided into manual and automatic, whichare used in small batch proofing and large batch PCBA processing, respectively.

The dispensingmethod of the dispenser is mainly changed according to the dispensing head.According to the dispensing pump of the dispensing head, the dispensing methodcan be divided into time pressure type, screw pump type, linear positive phasedisplacement pump type, spray Several different methods such as pump type. Thefollowing is a brief introduction to these different dispensing methods.

1. Time pressure

In many people'sminds, the air pressure pump has always been the most direct method of spotcoating in PCBA patch processing. It uses a compressor to produce a controlledpulsed air flow based on the principle of time and pressure. The longer theaction time of the air pulse during operation, the greater the proportion ofthe coating material pushed out from the needle.

2. Screw pump type

The screw pumptype dispensing head is highly flexible and suitable for dispensing variousPCBA patch adhesives. It is not sensitive to the air mixed in the patchadhesive, but it is sensitive to the change of viscosity. The dispensing speedalso has an effect on the consistency of dispensing.

3. Linear positivephase displacement

The linearpositive phase displacement dispensing head has good consistency to the gluepoint when it is applied at high speed. It can dispense large glue points butis complicated to clean, and is sensitive to the air in the patch glue.

4. Jet pump type

The jet pump typeis a non-contact dispensing head. The dispensing speed is fast, and it is notsensitive to the warpage and height changes of the PCBA substrate. However, thelarge glue point speed is relatively slow, requiring several sprays andcomplicated cleaning.