How to choose solder paste

The ratio of tin powder to flux in various solder pastes is also different. When choosing solder paste, different solder pastes should be selected based on the product being produced, production process, precision program for soldering components, and requirements for soldering effect;

 

B-1、 According to the relevant provisions of the "General Specification for Tin Lead Paste Solder" (SJ/T 11186-1998) in the electronic industry standard of the People‘s Republic of China, the percentage (mass) content of alloy powder in solder paste should be 65% -96%, and the measured value of the percentage (mass) content of alloy powder should not deviate from the predetermined value on the purchase order by more than/-1%. Generally, in actual use, the selected solder paste has a tin powder content of about 90%, that is, the ratio of tin powder to flux is roughly 90:10;

 

B-2、 Ordinary printing standards often use solder paste with a tin powder content of 89-91.5%;

 

B-3、 When using the needle dot injection process, solder paste with a tin powder content of 84-87% is often used;

 

B-4、 Reflow soldering requires firm soldering of device pins, full and smooth solder joints, and a solder climb of 1/3 to 2/3 in the height direction of the device (resistive capacitive device) end. The content of metal alloy in the solder paste affects the thickness of the solder paste after reflow soldering (i.e. the fullness of the solder joint)

）Has a certain impact; In order to confirm the existence of this problem, experts have conducted relevant experiments. As the metal content decreases, the thickness of the solder after reflow soldering decreases. In order to meet the requirements for the solder amount of the solder joint, a solder paste with a content of 85% to 92% is usually selected.