Precautions during reflow soldering process

In the electronic manufacturing industry, reflow soldering is a commonly used surface mount technology that can solder surface mount components (SMDs) to printed circuit boards (PCBs). The process of reflow soldering requires strict control of temperature and time, and adjustments should be made according to the requirements of solder paste and mounting components. When using reflow soldering for welding, attention should be paid to details such as temperature control, solder paste quality, component placement, welding time, cooling speed, and quality inspection. This article will provide a detailed introduction to the precautions that need to be taken during reflow soldering, in order to help readers better grasp reflow soldering technology and improve soldering quality.

1、 Reflow soldering

Due to the continuous miniaturization of electronic product PCB boards, chip shaped components have emerged, and traditional welding methods are no longer suitable for the needs. At first, reflow soldering technology was only used in the assembly of hybrid integrated circuit boards, and most of the components assembled and soldered were chip capacitors, chip inductors, mount on transistors, and diodes. With the continuous improvement of SMT technology and the emergence of various surface mount components (SMC) and surface mount devices (SMD), reflow soldering technology and equipment as part of SMD technology have also been developed accordingly. Its application is becoming increasingly widespread, and it has been applied in almost all electronic product fields.

Reflow soldering technology is not unfamiliar in the field of electronic manufacturing. The components on various boards used in our computers are soldered to the circuit board through this process. There is a heating circuit inside this device that heats air or nitrogen to a sufficiently high temperature and blows it towards the circuit board where the components have already been attached, allowing the solder on both sides of the components to melt and bond with the motherboard. The advantage of this process is that the temperature is easy to control, oxidation can be avoided during the welding process, and manufacturing costs are also easier to control.

2、 What are the precautions to take when using reflow soldering?

1. When producing different models, the width of the reflow soldering track should be adjusted first, using the joystick above the power switch, which depends on the width of the substrate. Generally, the width of the track should be about 1.5mm larger than the width of the substrate;

2. The temperature control range meets the specifications in the manual, and the control accuracy is within ± 2.0 ℃; The speed control meets the specifications in the manual, and the accuracy is controlled within ± 0.2m/min; The lateral temperature difference of substrate movement (≤ 150mm spacing) is within ± 10.0 ℃; The temperature zone parameters are basically determined based on the actual solidification effect, that is, the PCB welding area accounts for 90% of the effective area of the welding furnace steel mesh, and the belt speed is 75cm ± 10cm/s. When the PCB area is large, adjust the belt speed to achieve good welding effect. The general principle of adjustment is that when the PCB area is small, the net takeoff speed is slightly faster; When the PCB area is large, the net takeoff speed is slightly slower and should have good welding effect;

3. The appearance of the heater is complete and the electrical connection is reliable. The hot air fan operates smoothly and produces noise; The guide rail can be adjusted freely and kept parallel. The effective width of the transmission substrate meets the specifications in the manual;

4. The operating system is working normally, the appearance of the instruments and meters is intact, the indications are accurate, the readings are eye-catching, and they are within the qualified service life; The electrical equipment is complete, the pipelines are arranged in an orderly manner, and the performance is sensitive and reliable;

5. Curing or welding cannot be carried out immediately after starting up or adjusting the temperature, as the temperature has not yet reached or exceeded the set temperature, and immediate production will produce a lot of defective products; Only when the signal light is constantly on can the temperature inside the furnace reach the required temperature;

6. When the induction timeout or there is a substrate falling from the furnace, the alarm will sound. The furnace cover should be opened first to check if there is a substrate falling from the furnace. After clearing it, click on the interface to "release the alarm" and then click "reset";

7. Production conditions: For the safety of machines and products, production must not exceed the following range; The length and width of the substrate shall not be less than 50mm x 70mm and shall not exceed 310mm x 330mm. Cannot exceed the upper part of the track by 25mm and the lower part of the track by 18mm;

8. Usually, attention should be paid to protecting the touch screen of the machine to prevent malfunctions caused by heavy pressure and sharp scratches;

9. In case of alarm, chain overspeed operation, and sharp motor sound under unknown conditions, immediately press the red EMERGENCY STOP button to cut off the main power supply. Report to the manufacturer for resolution.

10. Reflow soldering manufacturers suggest that during the use of reflow soldering furnaces, the influence of external natural wind on dynamic temperature balance and welding quality should be avoided;

11. When sending out PCB workpieces from the reflow soldering furnace, it is necessary to avoid accidents that may cause burns to the operator's hands, as well as to prevent the accumulation of PCB boards at the outlet. Under the high temperature of the PCB board, due to falling or squeezing impact, the PCB board may fall off or the SMD devices with low welding strength may exit;

12. The reflow soldering manufacturer's daily maintenance work for the reflow soldering furnace: clean the surface of the equipment every day to make it pollution-free; Press the refueling button once a week and lubricate the roller chain with high-temperature lubricating oil (bio 30); During continuous production, at least twice a month: check the furnace motor and add high-temperature lubricating oil to each shaft;

13. Check whether the grounding wire connection of the welding machine is reliable before starting up every day;

14. After troubleshooting, turn on the main power supply of the equipment and turn the red mushroom shaped emergency stop switch clockwise to restore its original working state. When the reflow soldering furnace is turned off, it is not allowed to stop the PCB and conveyor belt inside the furnace under high temperature conditions. After the machine temperature drops, stop the conveyor belt.

The above is the relevant content on "Precautions during Reflow Welding Process" brought by this chip detection. We hope it can be helpful to everyone, and we will bring more exciting content in the future. The company's testing services cover various testing projects, including electronic component testing and verification, IC authenticity identification, product design and material selection, failure analysis, functional testing, factory incoming material inspection, and ribbon weaving. Welcome to call Chuangxin Testing, we will be happy to serve you.