SMT reflow soldering and process attention points

2021-11-07

Author：Downs

SMT is characterized by high PCB assembly density, small size and light weight of electronic products; reduced electromagnetic and radio frequency interference; improved production efficiency, reflow soldering should pay attention to compatibility with SMB, including pad wettability and SMB Heat resistance

SMT is characterized by high assembly density, small size and light weight of electronic products; reduced electromagnetic and radio frequency interference; improved production efficiency, reflow soldering should pay attention to compatibility with SMB, including pad wettability and SMB resistance Hot; Next, I will introduce the detailed content for you.

1. Features of SMT

1. High assembly density, small size and light weight of electronic products. The volume and weight of patch components are only about 1/10 of that of traditional plug-in components. Generally, after SMT is adopted, the volume of electronic products is reduced by 40%-60%, and the weight is reduced. 60%-80%.

pcb board

2. High reliability and strong anti-vibration ability. The defect rate of solder joints is low.

3. Good high frequency characteristics. Reduce electromagnetic and radio frequency interference.

4. It is easy to realize automation and improve production efficiency. Reduce costs by 30%-50%. Save materials, energy, equipment, manpower, time, etc.

2. Precautions for SMT reflow soldering

1. Compatibility with SMB, including pad wettability and SMB heat resistance;

2. The quality of the solder joints and the tensile strength of the solder joints;

3. PCBA welding working curve:

Preheating zone: the heating rate is 1.3-1.5 degrees/s, and the temperature rises to 150 degrees within 90-100s.

Heat preservation area: the temperature is 150-180 degrees, and the time is 40-60s.

Reflow zone: It takes 10-15 seconds to go from 180 to 250 degrees at the highest temperature, and it takes about 30 seconds to cool down quickly when returning to the heat preservation zone

Lead-free soldering temperature (tin, silver and copper) is 217 degrees.

What are the processes of PCBA processing and what should be paid attention to?

The process of PCBA processing is to communicate and consult first, and then evaluate the engineering process; assembly includes single product assembly, component integrated assembly, etc.; in addition, before operating the placement machine, you must understand the common labels of the placement machine.

One, the process of PCBA processing

1. Communicating consultation and matching materials;

2. Engineering process evaluation;

3. Quotation: The quotation at this stage is divided into three parts (PCB circuit board light board, electronic components, processing fee). Because it is a one-stop PCBA, all processes from engineering documents to finished products must be evaluated.

4. DFM file preparation; DFM (design for manufacturability) or processing technology manual.

5. Procurement of materials; the purchase of components by the patch processing plant will be centralized.

6. Warehouse; feeding, retrieving and preparing materials.

7. Processing; enter the actual production link,

8. Testing: The testing after PCBA manufacturing generally includes functional testing, burn-in testing, programming testing, signal testing, etc.

9. PCB assembly; assembly includes single product assembly, component integrated assembly, etc. In the assembly process, it is necessary to strictly control static electricity to cause damage to the finished product that has passed the test.

2. Precautions for PCBA patch processing

1. Before operating the placement machine, you must understand the common labels of the placement machine.

2. Before starting the placement machine, the operator should conduct a comprehensive inspection of the machine.