1. Product description:
3 layers of copper plate +1 layer of PCB plate welding ,The following 3 layers of copper (18 solder spots) +PCB (18 solder spots) are spot welded.

2. Assembly process:
Components → Install the first copper plate → Welding 1→ Install the second  and third copper plates → Welding 2→ Assemble PCB plate → Welding 3
Technological Requirements

3.Quality requirements for solder joints:
A. No cavity area or surface defects;
B. Good wetting of pins and pads;
C. Identifiable pin shape;
D. The front around the pin is required to be covered with 100% solder;
E. The filling degree of the perforated solder shall be 100%;
F.No dummy welding, false welding, pinhole hole, tin slag, tin beads, tin tip, cracks, incomplete penetration, short circuit, pad separation, golden scar solder joints, pins bending and other adverse conditions;
Welding time:
Single point welding time: 3-5s/ point
A. Do not interfere with other parts during welding;
B. Products can not be repaired, quality requirements first;
C. Traceability of welding products;
D. High cost performance.
The solution

4. Quality of solder joint
A. After testing, the copper plate heat dissipation is particularly fast, and ordinary low-power soldering iron head cannot meet the requirements. Only by adopting WELLER 200W high-power thermal conductivity technology and Weller preheating platform can the welding quality be guaranteed;
B. High activity of tin to solder content about 3.0%, effectively improve tin fluidity and tin penetration effectively improve production efficiency and quality.
Avoid uneven phenomenon of exposed solder pad and tin penetration;
C. Avoid oxidation and contamination on the surface of pads and pins to avoid binding of pads and pins to effective tin molecules during soldering.

5. Auxiliary fixture
A. Fixtures are made of imported high-density bakelite materials and anti-static, which are finished in one molding process with fine carving equipment to effectively ensure the accuracy of the fixture.
B. There is a timer in place to guarantee the preheating time, so as to effectively ensure the surface temperature of the product after preheating.

6. The welding head
Determine the factors of welding head service life: welding head structure shape.
Density of coating. Service temperature.
Corrosion degree of tin wire.
Solder time and other factors.
General domestic guarantee in 3W points above.
The import is more than 6W point.
(360 degrees.
Sn/Ag/Cu tin line with 3.0% flux).
For the smooth progress of the project, the following changes are suggested for the products and solder materials according to the product structure and equipment characteristics:
1. After product assembly, the relative position consistency error between PIN and shell is less than 0.2mm;
2. CCD visual positioning system is recommended to improve the accuracy;
3. During mass production, there should be no shaking of the copper plate, and the warping height should be less than 0.5mm;
4. High temperature resistance of all components: ≥180℃.