Before troubleshooting cold solder joints in Solar panel, it is essential to understand the fundamental process of string welding: under the action of the traction mechanism, the solder ribbon is precisely positioned directly above the main grid of the solar cell. The welding fixture is then placed, Pressure pins on the fixture apply force to the ribbon, ensuring contact with the cell's main grid. The assembly then moves under the string welding machine's lamp housing, where infrared heating melts the ribbon's solder. This melted solder bonds with the silver paste on the cell's main grid, forming a metallic alloy.

Note: For all cold solder joint investigations, prioritize checking for exposed white areas. If exposed white is present, address it first before evaluating the overall soldering quality.

I. Overall Cold Solder Joints on the Front Side

For overall cold solder joints on the front side, investigate the following:

1. Light Box Issues: Since this involves overall cold solder joints on the front side, focus on whether the light box's soldering parameters are abnormal or if the light box is aging. The key concern is whether it affects the overall soldering points.

2. Welding Height: During machine downtime, the lamp housing is raised to prevent over-welding of the underlying solar cells. When overall soldering failure occurs, check whether the distance between the lamp housing and the welding platform is appropriate. If the lamp housing is positioned too high relative to the welding platform during welding, it can reduce the efficiency of infrared heating, leading to soldering failure.

3. Welding Time and Power: Welding time and lamp housing power are critical factors affecting welding results. Prioritize investigating these parameters.

4. Flux Concentration: Abnormal flux concentration, particularly when too low, fails to clean oxides from the solder paste surface. This degrades soldering quality and causes overall cold soldering.

5. Material Defects: Abnormalities in incoming materials, such as defective solar cells, can cause soldering defects like insufficient solder or excessive solder. Uneven distribution of the solder paste layer on the ribbon may result in insufficient solder at thinner areas, preventing proper alloying with the silver paste on the solar cell. Expired or degraded flux fails to remove oxides from the ribbon, leading to soldering failure.

6. Fixture Abnormalities: Check fixture centering. Misaligned fixtures prevent pressure pins from adequately pressing the solder ribbon against the main grid, creating gaps that cause cold soldering. Inspect pressure pins for defects.

II. Single-Wire Solder Joint Failure on Front Side

For single-wire solder joint failures on the front side, investigate the following issues:

Note: Since it's a single failure, typically only the mechanism corresponding to the failed solder wire needs to be checked for abnormalities.

1. Traction issues: Loose traction collets, damaged traction collets, or worn traction collet bearings. Any malfunction in the mechanism corresponding to a single solder wire can cause misalignment, affecting the soldering result.

2. Support issues: Foreign objects in the support guide groove or solder wire rubbing against the support guide groove.

3. Fixture Issues: Check fixture integrity, wear on fixture pads, and abnormality of pressure pins.

4. Lamp Tube Issues: For isolated defects at fixed positions, inspect corresponding lamp tubes for abnormalities like aging or incorrect wattage.

5. Cutting Blade Issues: Inspect cut strips for bending or burrs. Both bending and burrs can cause strips to scrape against belts or other mechanisms, compromising weld quality.

III. Poor Front-End Solder Joints

For poor front-end solder joints, investigate the following issues:

1. Light Box Issues: Check if the light shield is deformed or obstructing the lamp tube, or if it is misaligned, causing the solder ribbon to melt prematurely before entering the light box—known as pre-melting—which similarly leads to poor front-end solder joints. Verify the power and welding time of the lamp tube soldering station.

2. Fixture Issues:Is the fixture warped or deformed? A warped fixture cannot apply sufficient pressure to the solder ribbon, making cold soldering more likely. Verify that all pressure pins fully contact the solder head and check for fixture slippage.

3. Solder Ribbon Issues: Is the solder ribbon deformed or overstretched? Deformation or overstretching causes bending, preventing alignment with the main grid on the solar cell and resulting in cold solder joints. Check for curled edges on the solder ribbon; curled edges cannot contact the main grid, causing cold solder joints.

4. Other Issues:Ensure moisture is fully dried after dicing.

IV. Faulty End Points

Investigate the following for end point failures:

1. Tension Issues: Wires are warped or overstretched.

2. Fixture Problems: Pin detachment, deformation, or jamming. Faulty points typically stem from defective fixture pins, preventing wires from contacting the main grid on the cell without pin support, thus causing cold solder joints.

3. Flattening issues: Flattening position too close to the feeding zone, or flattening plate rotation.

V. Back-Side Poor Soldering

Back-side poor soldering may stem from these issues:

1. Adhesion problems: Abnormal substrate adhesion causes relative displacement between the cell and ribbon during movement, resulting in back-side poor soldering (typically affecting the entire back surface).

2. Welding Base Plate Issues: Abnormal base plate leveling or severe wear; warped base plate magnets; misalignment between cell position and base plate.

3. Tail Clamp Issues: Tail clamp positioned too low, clamp jamming, failure to grip the solder ribbon, or foreign objects inside the tail clamp.

4. Lifting Mechanism Issues: Lifting mechanism jamming, damaged or leaking lifting cylinders, or abnormal lifting sealing tape causing the tape to bounce and shift during movement, preventing proper placement.

5. Welding Belt Issues: Belt wear, curled edges, or foreign objects under the belt can cause the back side tape to shift during movement of the cell and fixture, resulting in cold soldering.