Prevention and treatment of reflow soldering of SMT
Reflow soldering is the key process of SMT placement in the welding process You may encounter various unexpected situations during your work If proper handling methods and necessary measures are not taken, serious safety and quality accidents may occur
1. Precautions
1. The reflow furnace must fully reach the set temperature (green light on) before welding.
2. During welding, the temperature change of each temperature zone is often observed, with the variation range of ± 1 ℃ (according to the reflow furnace).
3. When the SMT chip processing equipment is abnormal, it should be shut down immediately.
4. The size of the base plate shall not be greater than the width of the conveyor belt, otherwise board card accidents may easily occur.
5. Before welding, SMT processing plant shall take protective measures (mask) or avoid reflow welding for parts that cannot withstand normal welding temperature according to the provisions of process files or component packaging instructions. After welding with manual welding or welding robot.
Circuit board

6. During SMT repair welding, strICtly prevent the conveyor belt from vibration, otherwise it will lead to component displacement and welding spot interference
7. Regularly measure the exhaust volume of the air outlet of the reflow soldering furnace. The air displacement directly affects the welding temperature.
2. Emergency treatment
1. Card board
1. If the plate is stuck, do not feed the plate into the furnace.
2. Open the furnace cover and take out the steel plate.
3. Find out the cause and take measures.
4. When the temperature reaches the required temperature, continue welding.
2. Alarm
If an alarm occurs, stop welding, check the cause of the alarm and deal with it in time
3. Sudden power failure
1. In case of power failure, do not send the plate into the furnace again. The conveyor belt or track will continue to run due to the support of various power supplies behind the UPS. After the surface mount plate runs to the furnace mouth and all the surface mount plates are connected, open the furnace cover and cool down, and then stop the machine.
2. Under unexpected circumstances, if the UPS fails, use a spanner wrench to clamp the square shaft rotating motor at the motor outlet, and take the PCB out of the furnace as soon as possible.
Why should SMT factory pay attention to the site
(1) "Three principles" of "site, existing and reality"
The continuous improvement of the site is considered to be the secret of the success of the Japanese company. The "three site principles" of "site, site and reality" reflect the importance of site and the concept of continuous improvement, and are widely used in Japanese enterprises. "Site" is the place where products are produced and services are provided; "Real things" are the main body of the website, which may be machine failures, unqualified products, damaged tools or customer complaints; "Reality" is to analyze real things on the spot and solve problems.
The "Three Presence Principles" emphasize that managers should go to the site to analyze and solve the problems of existing objects. When a problem occurs, the place to solve the problem should be the site, not the office or meeting room. On site, managers can usually find problems and take countermeasures in a timely manner by checking objects, observing, touching, feeling, and combining their own experience.
Give play to the role of the "three presence principle" and develop into the "five presence technology": on-site, physical, real, cash and current identification. The addition of "cash" and "cash confirmation" on the basis of the "three present principle" means that the results of on-site improvement will be converted into the amount to be confirmed, emphasizing the quantification of improvement results and cost awareness. The essence of the "Three Presence Principles" is to attach importance to the scene. As factory managers, we have learned that to solve on-site problems, we must go to the site.
(2) Laws for solving on-site problems
When solving on-site problems, the following steps should be followed, which is calLED the law of solving on-site problems here:
The first step is to go to the scene when problems occur;
The second step is to check the truth;
The third step is to take temporary measures on site;
The fourth step is to analyze the causes and find permanent countermeasures;
The fifth step is to regulate and prevent recurrence.

The above is the explanation given by the editor of pcb circuit board company.
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