Precision PCB Fabrication, High Frequency PCB, High Speed PCB, Standard PCB, Multilayer PCB and PCB Assembly.
The most reliable PCB custom service factory.
PCBA Tech
Technical guidelines for the use of SMT reflow soldering
PCBA Tech
Technical guidelines for the use of SMT reflow soldering

Technical guidelines for the use of SMT reflow soldering

2021-11-06
View:40
Author:Downs

1. Start of SMT reflow soldering

①Turn on the main power supply of the equipment (the air switch in the electric cabinet at the bottom left of the machine). Turn on the switch of the smoke exhaust system in the workshop to make it operate normally.

②Press the POWER button at the top right of the machine, turn on the computer, log in to the reflow soldering system interface, and after confirming that the system communication is normal, call the lead-free solder paste reflow soldering program. Check that the target temperature values (with lead) of the 8 heating temperature zones set for SV should be: 165, 160, 175, 185, 190, 190, 240, 200. The conveyor belt speed should be 75cm±10cm/min.

③Click the main start button on the interface of the reflow soldering control software, turn on the air transport, conveying, heating, and cooling switches to make the machine enter the running state.

④After the cooler is warmed up for 20 to 30 minutes, observe whether the actual temperature PV and the set value SV in the window are stable. If yes, proceed to the next step; if not, reset the PID parameter value of the temperature control table and set it at 5 After ~10 minutes, observe whether it is stable before proceeding to the next step.

Calibration is debugged by a technician. ①Put the thermometer and its 3 probes on the test board with the PCB size of the workpiece, and make it carry out the actual temperature measurement in the furnace along with the conveyor belt. The actual temperature of the board at the time point.

pcb board

②Compare the measured result in the previous step with the standard curve on the left. If the test curve is the same or similar to the standard curve, normal production can start; otherwise, retry setting the SV value on the temperature control table with a large temperature difference compared to the standard curve (Increase or decrease with a gradient of about 5°C), or adjust comprehensively in conjunction with the running speed of the conveying steel belt to achieve the workpiece temperature control curve required for actual production.

2. Description of each functional area of SMT reflow soldering

The first temperature zone-the preheating zone the second temperature zone-the preheating zone the third temperature zone-the preheating zone the fourth temperature zone-the drying zone the fifth temperature zone-the drying zone the sixth temperature zone-the activation zone the seventh temperature zone- The 8th temperature zone of the welding zone-rapid cooling zone

3. SMT reflow soldering set temperature zone temperature (SV value)

The first temperature zone—165 ±2℃ The second temperature zone—160 ±2℃ The third temperature zone—175 ±2℃ The fourth temperature zone—185 ±2℃ The fifth temperature zone—190 ±2℃ The sixth temperature zone— 190 ±2℃ The seventh temperature zone—240±2℃ The eighth temperature zone—200 ±2℃ The ninth temperature zone—room temperature air-cooled zone

Four, SMT reflow soldering temperature control table adjustment and setting

1. Set the main control value-move the mouse to the reflow oven control software HMI main screen, click in the temperature zone value window area that needs to be adjusted accordingly, and enter the required "SV" on the pop-up setting keypad Set value; press "OK" again to save and exit. The setting value range is "0~399".

2. Set PID parameters-Select the "Settings" menu option in the main screen of the reflow oven control software HMI, click the "Password" option in the drop-down menu, and enter the required "Username, Password" in the pop-up screen, and the system After confirming that the operator is a legal person (full-time engineering and technical personnel), you can start to enter the PID parameter setting: click in the numerical value window area of the corresponding upper and lower temperature zone of the reflow soldering furnace that has jumped out, and input the required number on the number keyboard that has jumped out P (or I)" parameter setting value; press "OK" again to save and exit. The setting value range is "0~399".

Five, SMT reflow soldering quality requirements

1. Welding components should not be displaced, skewed or erected due to vibration during the welding process.

2. The reflow soldering process time of PCB components should be controlled within 3 to 5 minutes.

3. The solder paste reflows well. The solder joints on the board surface after soldering should be bright and uniform, the solder can wet the pads, and the component leads should be uniform.

4. No PCB discoloration, copper foil warping, falling off and other undesirable phenomena.

6. Shutdown of reflow soldering

1. Under normal conditions:

①Check whether the PCB in the reflow soldering machine is completely soldered.

②Turn off the heating. After waiting for 20-30 minutes, click the switch to turn on and turn off the wind, conveying, heating, and cooling switches, and then turn off the computer.

③Or use the automatic delayed shutdown mode, just click the automatic shutdown button.

④Turn off the general power supply of the equipment (bottom left on the back of the machine).

2.In an emergency:

①Press the red mushroom-shaped emergency stop switch (EMERGENT STOP) on the left side of the machine.

②Turn off the general power supply of the equipment (bottom left on the back of the machine).

7. Matters needing attention:

1. The setting of the temperature zone cannot be adjusted at will. The temperature zone parameters listed above are basically based on the actual curing effect that the area of the welding pcb board accounts for 90% of the effective area of the steel mesh conveyed by the welding furnace, and the belt speed is 75cm±10cm/S. of. When the area of the processed pcb board is large, the belt speed should be fine-tuned to achieve a good welding effect. The general principle of adjustment is: if the area of the pcb board is small, the speed of the net take is slightly faster, when the area of the pcb board is large, the speed of the net take is slightly slower, and everything is subject to a good welding effect.

2. The PID parameters of the temperature control meter should not be set arbitrarily.

3. The inlet and outlet of the reflow soldering machine should be prevented from being blown in by natural wind during use, which will affect the dynamic temperature balance in the furnace and affect the quality of soldering.

4. When the PCB workpiece at the discharge port of the reflow soldering furnace is sent out, avoid the accident of scalding the operator's hand; also prevent the PCB board from accumulating on the discharge port, causing the PCB board to fall or the solder strength of the exported PCB board at a high temperature Low SMD components fall off due to falling or squeezing impact.

5. Do a good job in the daily maintenance of the welding machine equipment: clean the surface of the equipment daily to make it free of dirt, click the refuel button once a week in the manual mode of refueling, and lubricate the roller chain with high temperature lubricating oil (BIO-30); during continuous production, No less than twice a month: check to add high temperature lubricant to the furnace motor and each rotating shaft wheel.

6. Check whether the grounding wire of the welding machine is connected reliably before starting the machine every day.

7. After troubleshooting, turn on the main power supply of the equipment and turn the red mushroom-shaped emergency stop switch clockwise to return to the original working state. When shutting down, do not allow the PCB circuit board and the transmission steel mesh belt to stop in the furnace at a high temperature, and stop the conveyor belt after the temperature inside the machine drops!