From the mechanical point of view, different liquids and solids have different adhesion and cohesion. If the wetting force on the surface of the solid is greater than that of the wetting force on the solid surface, that is, if the wetting force is greater than that on the internal surface of the liquid. You can then tell whether a liquid and a solid are wet by the shape of their contact. Invasive electrons can form a tangent line along the surface of the liquid from the edge of the contact between the liquid and the solid, and the tangent line forms an angle between the liquid interior and the solid surface. If the included angle is acute angle, it is said to be wetted; if it is obtuse angle, it is said that it is not wetted.
In addition to mastering the basic welding knowledge in the process of PCB processing and welding, the following points should be paid special attention to.
① Do not scratch the gold-plated circuit pins with a knife, just scrub them with alcohol or clean them with rubber.
② Do not remove the pre-set short-circuit cable before soldering it to a CMOS circuit.
③ The welding time should be as short as possible, usually no more than 3 seconds.
④ The soldering iron used is 230 ° C.
⑤ The worktable should be antistatic.
⑥ Use thinner tips so that they do not touch adjacent endpoints when welding.
⑦ The safe welding sequence of pins and pins is grounding clamp output clamp power clamp input clamp
For SMT SMT SMT plug-in processing, the soldering steps are similar for surface mount components with relatively high pin density, that is, the pins are welded first, and then the remaining pins are soldered with tin. If the pin number is tight, pin to pin alignment is the key factor. High density bolts are removed with hot air gun. Clamp the components with tweezers, blow back all pins with a hot-air gun, and take out the components when the pins melt
