Introduction of the method of installing and welding light touch switch
Release time：2019-03-06 Clicks： Click
There are many ways to install and weld the light touch switch. We will introduce the welding method in detail.
As we all know, the light touch switch is to press the handle by external force to make the piston move, and the handle is transmitted to the shrapnel to move, so that the bubbles in the base are connected with the side bubbles, thus realizing the circuit conduction. And touch switch is welding installed on PCB circuit boards of various electronic products, to achieve the purpose of convenient life, then how is touch switch welded up, you will know after reading this article! ____________
First of all, we need to know that there are three kinds of welding methods: wave soldering, reflow soldering and manual soldering. We will explain them in three parts.
I. Wave soldering
Function: Used for welding of plug-in class (DIP) electronic components;
Welding equipment: wave soldering machine (commonly used in 3 temperature zone, 6 temperature zone, 8 temperature zone, 10 temperature zone, 12 temperature zone);
1. Insert the element into the corresponding element hole and put it into the conveyor belt.
2. Pre-coating flux for nozzle of conveyor belt to wave solder surface;
3. Enter the preheating zone (temperature 75-100 degrees Celsius);
4. Wave soldering (220-240 C);
5. Cooling: After leaving the solder wave, the solder joints are formed by natural cooling, and the welding is completed.
6. Removal of excess plug-in foot;
Second, reflow welding (temperature is easy to control, oxidation can be avoided in the welding process, and manufacturing cost is easier to control);
Function: Used for welding SMD electronic components.
Welding equipment: reflow welding machine (preheating zone, insulation zone, reflow welding zone and cooling zone)
1. Pre-coated solder paste;
3. Preheating zone;
4. Insulation zone;
5. Rapid heating zone;
6. Welding zone;
7. Cooling zone;
3. Manual welding
Function: Used for welding of plug-in class (DIP) electronic components
Welding equipment: electric soldering iron (high temperature, easy to weld but slow speed)
1. Preparing tools (soldering iron, solder wire, rosin);
2. Turn on the power supply and the isoelectric soldering iron reaches the welding temperature of 330-370 C.
3. After the temperature reaches, the soldering iron head is lighted with rosin and then soldered with tin.
4. Solder the rosin on the pin of the switch.
5. The foot is accurately mounted on the welding pad, and the fast spot welding area of the electric soldering iron is completed.
Abnormal product analysis of wave soldering and reflow soldering
I. Abnormal Peak Welding Products
1. pull point
(1) The preheating temperature of PCB board is too low, which makes the temperature of PCB board and components on the low side. When welding, the components and PCB absorb heat;
(2) Conveyor belt speed is too fast;
(3) poor flux activity;
(4) The socket hole is too large, and the welding foot does not match the socket hole.
2. continuous welding
(1) The distance between pads is too narrow;
(2) The pins of components are distorted;
(3) Conveyor belt speed is too fast;
(4) The flux activity is too poor;
3. virtual welding
(1) oxidation of welding foot or pad;
4. floating height
Deformation of weld foot;
(2) Conveyor belt speed is too fast and vibration;
(3) too large cartridge hole does not match the welding foot;
2. Abnormal reflow products
1. continuous welding
(1) Too much solder paste;
(2) Tapping the spacing of welding pads;
(3) The quality of solder paste is not good and the stickiness is too bad;
(4) poor printing;
The incorrect position of the patch will cause the phenomenon of continuous welding.
The pressure of patch is too high.
(2) Inadequate preheating temperature and high welding temperature will cause excessive thermal stress and micro-cracking of components.
3. solder joint:
(1) too few and uneven solder paste printing;
(2) pin deformation of components;
(3) Deformation of PCB plate and other factors can cause virtual welding.
(1) Asymmetric foot or pad;
(2) The position of the patch is incorrect;
(3) Uneven printing of solder paste;
(4) Vibration of conveyor belts and other factors will cause displacement.