Temperature control requirements for SMT reflow soldering of chips

In SMT reflow soldering, chip failures often occur, and the requirements for SMT reflow soldering of chips are relatively high. JEENOCE shares the temperature control requirements for SMT reflow soldering of chips here.

1、 After starting reflow soldering, it is necessary to maintain stable temperature and chain speed in each temperature zone before testing the furnace and temperature curve. It usually takes 20 to 30 minutes from cold start to stable temperature.

II The technical personnel of the SMT production line must record the furnace temperature setting and chain speed for each product or day, and regularly measure the furnace temperature curve and conduct controlled text testing to monitor the normal operation of reflow soldering. IPQC conducts inspections and supervision.

3、 Requirements for setting lead-free reflow soldering temperature curve:

The setting of SMT reflow soldering temperature curve is mainly based on: A. The recommended curve provided by the solder paste supplier. B. The material, size, and thickness of the PCB board. C. The density and size of components.

Lead free reflow soldering temperature setting requirements:

1. The installation point is within 100 points, without BGA, QFN, or other enclosed IC products, the pad size is within 3MM, and the measured peak temperature is controlled between 243 and 246 degrees.

2. For IC, QFN, BGA, and PAD products with more than 100 placement points and dense arrangement, their size should be greater than 3MM and less than 6MM. The peak temperature measured is controlled between 245 and 247 degrees.

3. There are more pin on ICs, QFNs, BGAs or PCB boards with a thickness of 2MM (inclusive) or greater, while the PAD size of a single special PCB product is 6MM or greater. According to actual needs, the measured peak temperature can be controlled between 247 and 252 degrees.

4、 FPC soft board, aluminum substrate and other special boards or parts have special requirements and need to be adjusted according to actual needs (product process and process instructions are special and controlled according to the process instructions)

Attention: When the actual working product is abnormal, it will immediately provide feedback to SMT technicians and engineers.

Basic requirements for temperature curve:

A. Preheating zone: The preheating slope is 1-3 ℃/SEC, and the temperature rises to 140-150 ℃.

B. Constant temperature zone: 150 ℃~200 ℃, maintain for 60~120 seconds

C. Reflux zone: 40-90 seconds above 217 ° C, peak temperature 230-255 ° C.

D. Cooling zone: Cooling slope less than 1-4 ℃/SEC (excluding PPC and aluminum substrates, actual temperature depends on the situation)

What are the precautions for setting the SMT reflow soldering temperature of chips

1. The glossiness, weldability, and weldability of the first five plates behind the furnace should be checked.

2. Model usage control: Strictly follow the "product process instructions" and customer requirements when using solder paste.

3. The temperature of the furnace must be measured in each shift, and the temperature of the furnace must be measured again after changing the production line. We need to measure the pre production model for each model. When adjusting the quality of the channel, it is necessary to confirm whether there are wooden boards or other foreign objects inside the furnace, and whether the width of the inlet and outlet is the same.

4. Each time the temperature parameter changes, a test of the furnace temperature is required.