1. Set temperature parameter process limits and reflow/wave soldering oven temperature settings:
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1.1 The engineer formulates a reasonable temperature curve test range based on the solder paste type, special component specifications, special measurement positions, FPC process, and customer requirements, including specific parameters and definitions for the heating zone, soaking (holding) zone, reflow zone, and cooling zone.
1.2 Preheating zone: This generally refers to the area from room temperature up to about 150°C. In this zone, the heating rate should not be too fast, generally not exceeding 3°C/second, to prevent substrate deformation or micro-cracking of components due to rapid heating.
1.3 Soaking (holding) zone: This generally refers to the area from about 110°C to 190°C. In this zone, the flux further volatilizes and helps the substrate remove oxides, and both the substrate and components reach thermal equilibrium, preparing for high-temperature reflow. This zone typically lasts 60–120 seconds.
1.4 Reflow zone: This generally refers to the area above 217°C. In this zone, the solder paste melts quickly, rapidly wets the soldering surfaces, and forms a new alloy solder layer with the substrate pads, achieving good soldering between components and pads. This zone is typically set to last 45–90 seconds. The maximum temperature generally does not exceed 250°C (unless specific requirements exist).
1.5 Cooling zone: This zone rapidly cools the solder joints, solidifying the solder, refining the solder grain structure, and improving soldering strength. The cooling rate in this zone is generally set to about -3 to -1°C/second.
1.6 Set the zone length, zone temperatures, and conveyor speed for the reflow/wave soldering oven.
2. Fabrication of the temperature measurement board
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2.1 Use a sample board identical to the production part number as the temperature measurement board. When fabricating the measurement board, in principle, necessary representative temperature-measuring components should be retained to ensure that the measured temperature is consistent with the actual production temperature.
2.2 If the measurement board cannot be kept consistent with the production part number, a similar type of measurement board may be used for measurement after verification and approval by the engineer.
2.3 Temperature measurement points should be selected at the most representative areas and components, such as components with the largest and smallest heat absorption. Component selection priority (e.g., Socket -> Motor -> Large BGA -> Small BGA -> QFP or SOP -> Standard Chip). In addition, a measurement point should also be selected between these two extremes.
2.4 Generally, there should be no fewer than 3 measurement points per board; for boards with BGA or large ICs, at least 4 points should be selected, prioritizing special representative components.
2.5 Position distribution: Use a full-board diagonal pattern or a 4-corner plus 1-center pattern to cover the entire board's position distribution.
2.6 Thermocouple wires should be secured to the measurement board using high-temperature yellow tape or red adhesive.
3. Testing the oven temperature curve
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3.1 Based on the temperature process limits established by the engineer, the oven temperature curve testing technician pre-sets the temperatures of each zone according to the different reflow oven structures to meet the temperature process requirements.
3.2 Insert the thermocouples on the measurement board sequentially into the sockets of the tester. Put on the protective cover, and note that the air wire must be inserted into the first socket.
3.3 After setting the oven temperature, wait until the green light on the reflow oven is normally lit before using the measurement board for testing.
3.4 Carefully place the measurement board and tester onto the conveyor belt or chain of the reflow oven, and turn on the tester's power and data recording switch. The board entry method should be the same as that for the boards being produced.
3.5 After testing is completed, remove the tester at the board exit end.
3.6 Read the temperature curve on the computer and check whether the curve is within the reasonable process range. If not, the technician needs to continue adjusting the temperatures of each zone until a temperature curve that meets the process limits is measured.
4. Data collection
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1. Open the computer KIC temperature measurement program as shown in the figure, and check whether the solder paste process is OK.
2. Enter relevant information including oven temperature, zones, conveyor speed, test channels, etc.
3. Connect the temperature tester as prompted and start reading data.
4. Analyze the data according to the temperature curve requirements, and print the temperature curve that meets the requirements for archiving.
5. Fill in the "Temperature Curve Confirmation Form," and after joint confirmation by ME and IPQC, post it on the reflow oven.
5. Post-oven inspection
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Inspect the soldering condition of the substrate after passing through the oven under this temperature setting, and confirm the reasonableness of the set range and oven temperature parameters based on the soldering yield.
6. Test frequency: Can be automatically selected from 0.05–30 MIN
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The reflow oven temperature curve is tested once daily by the technician. If the line is changed, it should be re-tested, and the correct temperature curve should be printed and the corresponding "Temperature Curve Confirmation Form" filled out.
7. Precautions:
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7.1 If the customer requires measuring IC/QFP temperature, the thermocouple wire should be connected to the IC pins.
7.2 If the customer requires measuring BGA temperature, drill a hole at the BGA pad position on the front of the test board through to the back, insert the thermocouple wire from the back of the test board and solder it to the BGA solder joint, while also soldering the entire BGA onto the test board.
7.3 If measuring the temperature of hand-soldered components is required, pass the thermocouple wire through the solder hole from the front, extending 1.5–2 mm beyond the test board so that it can contact the solder wave.
7.4 Pay attention to safety during testing to prevent high-temperature burns.
7.5 If there are any questions, please contact our after-sales service.
