1. Storage and use:

1) When printing glue, add a small amount multiple times. After production, the glue on the steel mesh can no longer be used. The glue still in the package should not be used within 24 hours and should be returned to the refrigerator, but it should not be used more than 4 times, otherwise it will be scrapped.

 

2) The glue must be certified.

 

 

3) The glue must be stored at low temperature (2～8℃); it must be warmed up before use. The 10ml package needs to be warmed for more than 2 hours, the 30ml package needs to be warmed for more than 4 hours, and the 300ml package needs to be warmed for more than 12 hours.

 

2. Dispensing defects and influencing factors

1) Glue dot shape and its shape retention

The shape of the glue dot and its shape retention are mainly related to the viscosity and thixotropic properties of the glue itself, in addition to the parameter setting of the machine and the ambient temperature and humidity. Proper viscosity and thixotropy characteristics can have good shape retention, no flow and collapse after sizing, no tailing phenomenon in the sizing process, so as to avoid contamination of the pad and avoid false soldering.

 

To maintain a good viscosity, you must pay attention to the temperature recovery time, the ambient temperature and humidity, and avoid moisture absorption, so as to reduce the chance of curing bubbles and reduce the possibility of wave soldering.

 

2) Bonding strength

Refers to the ability of the glue to resist vibration or impact and wave soldering shock waves after curing. This mainly depends on the glue itself. The process factors that should be paid attention to when using are:

 

a. Contact area

According to the external dimensions and weight of the component package, select the corresponding dispensing quantity and glue dot size.

 

b. Type of component backplane

Some components use glass, ceramic, etc. bottom plates. Because of the silicone oil release agent residue on the bottom spots, the bonding force between the bottom plate and the glue is low. Optional anti-release agent glue.

 

c. Curing curve

The curing temperature and time of different grades of glue are not exactly the same. The temperature and time should be set according to the specific requirements of the supplier, the thickness of the PCB, the distribution of the components, etc.; the curing temperature of the same glue will be different, and the corresponding time will be different. For example, the glue of 3609 needs 90sec at 150℃, while It takes 3 min at 125°C. The glue with good moisture resistance can choose a higher curing temperature and a faster temperature rise rate, and the corresponding curing time can be shortened. On the contrary, the glue with poor moisture resistance can choose a lower curing temperature and a slower temperature rise rate. The curing time should be long.

d. The condition of the PCB board

The surface of the PCB board should be clean and pollution-free; the solder mask has a strong affinity with the glue.