1) The following view is the BGA chip welding process diagram

BGA diagram just after mounting→BGA diagram when the soldering temperature reaches the melting point→BGA diagram after reflow

 

    Through the above schematic diagram of the BGA soldering process, we can find that after the BGA chip is soldered, there is enough space at the bottom of the PCB and the chip to allow the liquid to flow through the bottom. The shortcomings of the BGA chip mentioned in the article are high sensitivity to humidity, fragile structure, poor fatigue resistance of solder joints, poor shear stress of solder joints, and reduced reliability after soldering to provide the reliability of our electronic products. sex.

2) Specific implementation methods

According to the characteristics of the bottom potting glue we choose, I recommend the following methods:

*Glue for metering pump

The metering pump can pour the metered potting glue quantitatively between the CSP/BGA chip and the substrate, and the metering pump can ensure continuous and consistent dispensing volume. Glue is poured on the four sides of the chip by pouring. This method can provide good fillet molding and is faster than single-sided or L-shaped pouring.

Pouring around the chip. If the output is small, optical magnification equipment can be used to locate the position of the glue head on each side of the chip to reduce the chance that the glue nozzle cannot accurately fill the glue; if the output is large, you can use the three-axis Automatic potting equipment to achieve mass production.

The use of metering pumps for filling glue requires a large initial investment, generally between hundreds of thousands and hundreds of thousands, but it can save labor and labor costs and ensure product consistency.

*Glue filling by manual dispenser

The manual glue dispenser realizes the dispensing of glue by controlling the time and air pressure, and cannot guarantee the continuous and consistent dispensing volume. If there is no need to strictly control the consistency of the product's glue ejection and the output is not large, and from the perspective of saving production costs, I recommend using a manual glue dispenser to achieve bottom glue filling. Because the investment of a manual dispenser ranges from more than 1,000 to 3,000 to 4,000, the initial investment is relatively low.

 

 

Special considerations: Before the formal production, I suggest that it is best to carefully evaluate the amount of glue that needs to be poured at the bottom of each chip, so that quantitative management of the product can be realized, which can avoid the waste of glue and the pollution of the PCB. Different companies and enterprises can choose different filling methods according to their actual conditions, and the production cost has been optimized.