The basic principle of reflow soldering is simple. First, it prints the solder paste on the surface of the surface mounting element of the PCB plate, and then puts the SMD on the solder paste prepared by the automatic patch machine. Finally, through the reflow soldering furnace, gradually heated in the reflow furnace, the solder paste was melted, called reflux, and then the PCB plate was cooled, the solder was solidified, and the components and pads were firmly welded together.
A good reflux temperature curve must be provided to achieve good reflow soldering effect. So what is a good reflux curve? A good reflux curve should be a good welding for all the surface mounting elements on the PCB plate to be welded, and the solder joints not only have good appearance quality but also have good internal quality temperature curves.
The characteristics of solder paste determine the basic characteristics of the reflux curve. The solder paste (Flux) has different chemical components because of different solder paste, so its chemical changes have different temperature requirements, and there are different requirements for the reflux temperature curve. Generally, the solder paste supplier can provide a reference reflux curve, and on this basis, the user can optimize the standard of a reflux curve based on its own product characteristics or the IPC/JEDEC J-STD-020 reflow furnace temperature gauge specification. How to test the temperature of reflow soldering?
1.KIC2000 furnace temperature tester
Non real time thermometer, through sampling and storage, then uploads the collected data to the computer for analysis.
A medium used to feel the temperature of the environment. The principle of its working principle is to make up the circuit of two kinds of conductors with different components. When there is a temperature difference between the temperature measuring end and the reference end, the thermal current will be produced in the loop, and the change of the external temperature is reflected by the size of the current. The thermocouple usually requires smaller diameter, because the small diameter of the mass is small, the response is fast, and the result is more accurate.
3. other tools
High temperature solder, high temperature adhesive tape, data transmission line and so on.
Test point selection principle
Due to the different components of the circuit board and the flow of hot air in the furnace, the temperature of all parts on the board is not the same. Therefore, it is necessary to choose the suitable test point in real and comprehensive measurement of the temperature of the measured product. The following principles are generally followed.
1. conditions are allowed to select test points as much as possible.
2. the measured point is on the same longitudinal axis as far as possible.
3. components with special requirements for temperature;
The position with the highest temperature of 4. plate surface;
5. the lowest temperature of the plate surface.
1. select the appropriate test points;
2. fix the thermocouple on the circuit board according to the requirements of the tester, and fix it well. The circuit board selects the fully attached product.
3. select solder paste and set the parameter value in the test software. Connect the tester to the main control PC and complete the operation according to the prompt on the software.
4. the circuit board and tester are sent into the furnace for testing. At this time, the temperature of the temperature zone is consistent with the predicted temperature.
5. the data line will be connected and the furnace temperature data will be transmitted after the furnace is released. After the transmission is completed, the furnace temperature curve will be simulated.
6. by adjusting the temperature to achieve the appropriate temperature zone, and then test the instrument cooling after testing, no doubt after the production.