How to Fix Solder Not Flowing During Laser Soldering? ​

How to Fix Solder Not Flowing During Laser Soldering?

With the widespread adoption of automated equipment, an increasing number of automated products are being implemented in production lines. Automatic soldering systems, as the name suggests, are automated welding equipment systems that offer significant advantages over traditional manual soldering irons.

The core component of an automatic soldering system is its welding mechanism, which primarily relies on laser soldering software for backend configuration and operation. This not only enhances soldering efficiency but also improves weld quality—producing fuller, more precise solder joints without overflow—making it widely adopted in various industries.

So, what causes the solder to fail to flow during the operation of an automatic soldering system?

Causes of Solder Not Flowing During Laser Soldering

1. Pre-soldering Scrubbing: If the leads of the component to be soldered are contaminated with oil or rust, they will not wet properly. Even if a small amount of solder paste is applied, it may result in a cold joint. Before dipping the pins in rosin, first scrape off the flux and rub the pins back and forth with a tinned soldering iron tip until a thin solder layer forms on the pins. Most modern electronic components have good solderability, so manual soldering generally doesn't require pre-tinning (provided flux-core solder wire is used). However, if components are stored improperly, causing oxidation or contamination of the pins, pre-soldering treatment becomes necessary.

2. Firm Holding Without Shaking: The soldering material must be held firmly and securely. Particularly, the material must not be moved during the solder solidification stage, as shaking during solidification can easily cause cold joints. The solder joint may appear crumbly like bean dregs. To stabilize your wrist, rest it on a support and maintain an upright sitting or standing posture.

3. Applying  Appropriate Amount of Solder: The amount of solder applied should be sufficient to cover the joint according to its size. If one application is insufficient, additional solder can be added. However, the soldering iron must be removed only after the new solder has fully melted and blended with the existing solder. Some operators apply excessive solder that piles up like a swallow's nest, resulting in many weak solder joints.

4. Mastering Temperature Control: If the temperature is too low, the solder wire will have poor fluidity; if the solidification temperature is too high, the solder may drip. The solder must properly adhere to the joint.

5. Minimizing Use of Solder Paste: As an acidic flux, solder paste must be wiped off after soldering; otherwise it may severely corrode the circuit and cause broken joints. Therefore, its use should be minimized. When using rosin-free solder bars, rosin serves as a better flux. After soldering with the iron, apply rosin and quickly perform the soldering. Alternatively, a flux can be prepared by mixing 95% alcohol with rosin. This solution can also be brushed onto cleaned solder joints for printing.

The above five points can basically solve the problem of solder not flowing during laser soldering. Songsheng Opto-Electronics' semiconductor-grade constant-temperature coaxial monitoring soldering head equipped with a PID online temperature regulation feedback system can effectively achieve constant-temperature soldering, ensuring high yield and precision in soldering quality.

Songsheng Opto-Electronics Coaxial Temperature-Measuring Vision Single-Focus Laser Soldering Head

The temperature control principle of Songsheng Opto-Electronics' laser soldering system is as follows: Through infrared detection technology, it monitors the infrared thermal radiation generated by the laser on the workpiece in real time, forming a closed-loop control system for laser soldering temperature and detected temperature. Songsheng's independently developed control board with PID regulation function can effectively maintain the laser soldering temperature within the set range with minimal fluctuation.