PCB Technical - Analysis on the BGA ball planting process in pcb assembly processing​

Analysis on the BGA ball planting process in PCB assembly processing
Usually, when you inspect a PCB assembly manufacturer or smt chip factory in China, what do you look at? Many people follow the business or engineering of the chip processing factory to walk through the scene and visit the workshop. If it is more strict, they may see whether the storage of BGA, components, and solder paste is standardized, and whether the packaging is anti-static. Few people will notice the BGA repair station and its supporting X-ray film. If the PCB assembly processing plant does not have a BGA repair station, if your circuit board happens to have a lot of BGA and IC chips, then you pray that there will be no bad chips during the entire soldering process!

Therefore, it is necessary to have a check on the BGA repair station and BGA repair, not to distrust your supplier, but to prevent everything from happening and reduce unnecessary troubles, so do you know a lot of people for BGA repair? If not, Baiqiancheng Electronics will share the little knowledge with everyone.

BGA's repair ball placement is also called ball placement. Specific steps are as follows:

1. Remove the residual solder on the BGA bottom pad and clean it

(1) Use a solder removal tape and a shovel head to clean the residual solder on the flat BGA bottom plate, and be careful not to damage the pad and solder mask during operation.

2. Clean the flux residue with isopropanol or ethanol.

2. Apply paste flux or printing solder paste on the BGA base plate

Paste flux is used for bonding and fluxing. Sometimes, solder paste can also be used. When using solder paste, the metal composition of the solder paste should be the same as the solder ball. Using BGA special small template, SMT patch printing must check the printing quality, if it is unqualified, it must be cleaned and reprinted.

Three, choose solder balls

When selecting solder balls, the material and diameter of the solder balls will be considered. The current lead PBGA solder balls are 63Sn-37Pb; lead-free BGA

Sn-AGCU is used; CBGA is a high temperature solder of 90Pb10Sn, so it is necessary to choose a solder ball of the same material as the solder ball of the BGA device.

If you use a paste flux, choose a ball with the same diameter as the BGA device ball: If you use a paste flux, choose a BGA device ball with a smaller proportional diameter.

Four, put the ball

There are four methods for pendulum ball: flip-chip method, regular method, manual installation of solder balls and printing of proper amount of solder paste;

Then flow soldering to form solder balls. These are several common methods for BGA repair of SMT welding defects in our PCB assembly factory.

(1) Upside-down method (using ball putting equipment).

a. If there is a ball sticking device (also called a ball sticking device), you can choose a template that matches the BGA pad. The opening size of the template should be greater than the diameter of the solder ball by 0.05～-0.mm; spread the solder balls evenly on the template and shake The ball setter rolls the excess solder balls from the template to the solder ball collection groove of the ball setter, so that only one solder ball remains at each leakage point on the surface of the template.

B. Place the ball setter on the workbench of the BGA repair equipment, and place the BGA device printed with paste or solder paste on the suction nozzle of the BGA repair equipment (the plate printed with paste or solder paste faces down), Turn on the vacuum to suck firmly.

C. Align according to the method of installing BGA, so that the bottom image of the BGA device is completely overlapped with the image of each solder ball on the surface of the solder ball template.

D. Move the suction nozzle down to make the pad at the bottom of the BGA device contact the solder ball on the surface of the ball sand template, and the solder ball adheres to the corresponding pad of the BGA device by the viscosity of the paste or solder paste

e. Clamp the frame of the BGA device with tweezers and turn off the vacuum pump.

f. Place the solder ball of the BGA device face up on the equipment workbench.

G. Check whether there is a lack of solder balls on each solder pot of the BGA device, and whether there is metal filling

Analysis of the BGA rework and ball placement process inPCB assembly processing, the electronic editor will introduce this to you, if you are interested in our content, you can follow us and learn more about PCB assembly information, thank you.