Analysis On The Causes And Treatment Methods Of Empty Spots In SMT Patch Dispensing

In the SMT process, the dispensing process is prone to various defects such as plaque, which is one of the common defects. The presence of a dispensing point will result in a decrease in bond strength and open the path of solder penetration under the component, causing failures such as bridging and shorting. So what is the reason for the SMT patch allocation blank? How to deal with it? Cinda will introduce you.


The main reasons and treatment methods for plaque in SMT dispensing:

1. There is a large mass in the glue that blocks the nozzle of the dispenser; or there are bubbles in the glue, as well as blank spots. The treatment is to use film glue to remove excess particles and bubbles.

2. When the viscosity of the film adhesive is unstable, coating is performed, and the coating amount is unstable. Precautions: After each use, put it in a closed container to prevent condensation for about 1 hour, then install the dispensing head and then start dispensing after the nozzle temperature has stabilized. It would be better if you use a temperature control device. 

3. If the dispensing head is not used for a long time, the solubility of the patch adhesive must be restored. In the first few times, dispensing was definitely not enough. Therefore, each printing plate and each dot are coated. When using for the first time, you must first boot multiple times.

4. When the needle transfer method is used to dispense glue, the exposed area is large because the glue is open. SMD glue absorbs moisture easily. The incorporation of air is caused by improper handling of the patch adhesive, especially self-filling patch adhesives. The treatment method is to use low temperature and slow curing, and the heating time is long, which can help the water to be used up before curing to avoid void formation.