In SMT chip processing, some special components and processes using normal solder paste printing process may have some problems, which may affect the later use efficiency. In order to prevent this kind of problem in advance, we need to do some treatment, so with the SMT chip technology, we need to use the dispensing process. You may know about dispensing process, but has anyone known about dispensing machine?
Today, Dafton-SMT will share the knowledge of dispenser with you. Dispensing machine can be divided into manual and automatic. Manual dispensing machine is used for test or small batch production, and automatic dispensing machine is used for large batch production. The following describes the dispensing head, the most important part of the dispensing machine, and the general technical parameters of the dispensing machine.
1. Dispensing head. The dispensing head can be divided into four types according to the different distribution pumps: pressure type, screw pump type, linear positive phase shift pump type and jet pump type.
1) Time pressure dispensing head. For a long time, the air pressure pump has been considered as the most direct spot coating method. It uses the compressor to generate controlled pulse air flow to work according to the principle of time and pressure. It has a syringe with a needle at the end. The longer the air flow pulse works, the more coating materials will be pushed out from the needle.
2) Screw pump dispensing head. The screw pump type dispensing head is flexible, suitable for dripping all kinds of patch adhesives, not sensitive to the air mixed in the patch adhesive, but sensitive to the change of viscosity, and the speed of spot coating also has an impact on the consistency of spot coating.
3) Linear positive phase displacement dispensing head. When the linear positive phase displacement dispensing head is applied at high speed, it has good consistency to the glue point, can spot large glue point, but the cleaning is complex, and is sensitive to the air in the patch glue.
4) Spray pump dispensing head. Spray pump type is a non-contact dispensing head, which is fast in dispensing speed and insensitive to PCB warpage and height change. However, the speed of large dispensing point is slow, which requires multiple sprays and complicated cleaning.
2. General technical parameters of dispensing machine. The conventional technical parameters of dispensing machine include dispensing amount, dispensing pressure (back pressure), needle size, distance between needle and PCB board, glue temperature, glue degree, curing temperature curve and bubble, etc.
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