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Test method and steps of real-time temperature curve

Test method and steps of real-time temperature curve

① Prepare a actual product surface soldered pcb assembly board .

Because printed solder paste and the PCB assembly board without soldering cannot fix the test end of the thermocouple, it is necessary to use the soldered actual product for testing. In addition, the test sample cannot be used repeatedly, and it should not be used more than 2 times. In general, as long as the test temperature does not exceed the limit temperature, the assembled board that has been tested 1 or 2 times can also be used as a formal product, but it is absolutely not allowed to repeatedly use the same test sample for testing for a long time. Because after a long period of high temperature welding, the color of the printed board will become darker, and even become brownish brown. Although the heating method of the full hot blast stove is mainly convection conduction, there is also a small amount of radiation conduction, and the dark brown absorbs more heat than the normal fresh light green PCB. Therefore, the measured temperature is higher than the actual temperature. If in lead-free soldering, it is likely to cause cold soldering

② Select the test point.

According to the complexity of the PCB assembly board and the number of collector channels (generally, the collector has 3 to 12 test channels), select at least three that can reflect the high (hottest), medium, and low (coldest) of the PCB surface assembly (Points) are representative temperature test points.

③The highest temperature (hot spot) is generally in the middle of the furnace, where there are no components or few components and small components; the lowest temperature (cold spot) is generally at large components (such as PLCC), large areas of copper, transmission rails or the edge of the furnace hall, Where hot air convection cannot blow.

④ Fixed thermocouple. Use high-temperature solder (Sn-90Pb, solder with a melting point exceeding 289 ° C) to solder the test ends of multiple thermocouples to the test points (solders) .The solder on the original solder joints must be removed before welding; or use high temperature tape will stick the test ends of the thermocouples to the temperature test points of the PCB. Regardless of which method is used to fix the thermocouples, it is required to ensure that they are soldered, glued, and clamped firmly.

⑤ Insert the other end of the thermocouple into the 1,2.3…. Jacks on the machine table or into the socket of the collector, taking care not to reverse the polarity. Number the thermocouples, and keep in mind the relative position of each thermocouple on the surface mount board and record it.

⑥ Place the PCB assembly board under test on the conveyor chain / mesh belt at the entrance of the reflow welder (if using a collector, place the collector behind the surface PCB assembly board, leaving some distance slightly above 200mm) Then start the KIC temperature curve test program.

⑦ As the PCB runs, draw (display) real-time curves on the screen (when the device comes with KIC test software).

⑧After the PCB runs through the cooling zone, hold the thermocouple wire and pull the PCB assembly board back.At this time, a test process is completed, and the complete temperature curve and peak temperature / timetable are displayed on the screen (if a temperature curve collector is used, Then take out the PCB and collector from the reflow oven exit, and then read out the temperature curve and peak temperature schedule through software).

⑨ Enter the file name and save it.

⑩ You can also print out the real-time temperature curve.

11月-29-2019

FASTPCBA