In order to ensure the welding quality, the key is to set up the temperature curve of the reflux furnace of the reflow welder. How to set up a reasonable temperature curve as soon as possible in the face of a new small type of backflow welder? Now, guangshengde will give you some answers:

1. small reflow temperature test tool

Before setting the temperature curve, it is necessary to prepare the temperature tester, as well as the matching thermocouple, high temperature solder wire, high temperature tape and SMA to be measured. The small type backflow furnace has a temperature tester. The temperature change in the furnace cavity can be clearly seen on the control panel, which makes the test temperature curve very convenient. However, in order to correspond to different SMA, different temperature measurement samples and special thermocouples are needed. The small diameter thermocouple used in this kind of tester has small heat, fast response and accurate measurement results.

2. position and fixing method of thermocouple

Where is the thermocouple welded? How to weld? In principle, thermocouple should be set at the welding pad of components with large thermal capacity. In addition, thermocouple should be set at the neutral position of PCB for the shell of thermal sensitive device to observe the temperature distribution of the layout.

The good way to fix thermocouple on PCB is to weld with high temperature solder paste (sn96ag4) at the place where the temperature is measured, or fixed with high temperature tape, but the effect is not as good as that fixed with high temperature solder paste. According to the size and complexity of SMA, 5 or more thermocouples are symmetrically set on PCB, so that the heating condition of SMA board surface can be accurately understood.

3. solder paste performance

In order to set the reflux temperature curve correctly, the performance parameters of the solder paste used must be considered. It is the melting point of the alloy, and the high temperature in the reflux zone is determined according to the melting point of the alloy, that is, 30-40 ℃ higher than the melting point of the alloy. Secondly, the active temperature and duration of solder paste should be considered to set the temperature and duration of preheating zone, so as to ensure that the flux remains active in reflow welding.

4. structure of reflux furnace

For the small type of small type backflow furnace for the first time, the internal structure and heating characteristics of the furnace should be understood. It is necessary to see several heating temperature sections, how long each heating section can last, how much temperature high energy can be reached, the position of thermocouple placed, the characteristics of hot air formation, how to adjust the wind speed and the hot air circulation path. It is helpful to know these key parameters for setting the reflux temperature curve.

When using a small bench type reflux furnace, SMA is in a fully static state, and the heating time of each temperature zone is completely determined by the heating program, which can determine the accurate heating time for each heating zone.