PCBA Tech - SMT quality issues and welding process equipment and materials

Reasons for SMT chip processing quality problems

The common quality problems of SMT patch include missing parts, side parts, overturned parts, offset, damaged parts, etc. Let's learn more about the causes of SMT patch quality problems.

1. The main factors that lead to patch missing parts:

1, the component feeding rack is not in place;

2, the air path of the component nozzle is blocked, the nozzle is damaged, and the height of the nozzle is incorrect;

3, the vacuum circuit of the equipment is faulty and blocked;

4, the circuit board is poorly purchased and deformed;

5. There is no solder paste or too little solder paste on the pads of the circuit board;

6, component quality problems, the thickness of the same variety is inconsistent;

7. There are errors or omissions in the call program of the placement machine used in the placement process, or the selection of the component thickness parameters during programming is wrong;

8. Human factors accidentally touched off.

Two, the main factors that lead to the overturning and side pieces of SMC resistors:

1, the feeding of the component feeder (feeder) is abnormal;

2, the height of the nozzle of the placement head is wrong;

3, the height of the placement head grabbing material is wrong;

4. The size of the loading hole of the component braid is too large, and the component is turned over due to vibration;

5. The direction of the bulk material is reversed when it is put into the braid.

Three, the main factors leading to component placement deviation:

1. When programming the placement machine, the X-Y axis coordinates of the components are incorrect;

2. The suction nozzle of the patch makes the suction unstable.

Fourth, the main factors that cause damage to components during placement:

1, the positioning thimble is too high, the position of the circuit board is too high, and the components are squeezed during mounting;

2, when programming the placement machine, the Z axis coordinate of the component is incorrect;

3. The nozzle spring of the placement head is stuck.

Process equipment and materials required for SMT chip processing and welding

SMT chip processing welding quality is determined by the welding method, welding materials, welding process technology and welding equipment used. SMT chip processing is based on the supply method of molten solder. The soft soldering technology used in SMT chip processing mainly includes wave soldering and reflow soldering.

The basic difference between wave soldering and reflow soldering in SMT chip processing lies in the different supply methods of heat source and solder.

In SMT chip processing wave soldering, the solder wave crest has two functions: one is to supply heat, and the other is to provide solder.

In SMT patch processing and reflow soldering, the heat is determined by the heating mechanism of the reflow soldering furnace itself. The solder paste is first applied in a certain amount by the SMT dedicated equipment, and the wave crest of the SMT patch processing plant is used. Machine, flux, reflow soldering machine.

SMT chip processing reflow soldering is a very critical part of the process flow. Through SMT processing, the solder paste pre-allocated on the PCB pad is remelted to realize the mechanical interaction between the solder ends or pins of the surface assembly components and the PCB pads. Solder points for electrical connections. Reflow soldering furnace used in SMT chip processing, related materials include solder paste, nitrogen, etc.

If the entire process of SMT patch processing cannot be controlled well, it will have a catastrophic impact on the reliability and service life of the products produced.