The Essence of Dip Soldering Lies in Dynamic Heat Conduction and Wetting Balance

Dip soldering is not simply pressing a board into a solder pot; it requires PCB pins to pass vertically and at a constant speed through a pre-applied Flux coating before precisely contacting the surface of the molten solder. The entire process—heat transfer, oxide film rupture, solder climbing, and formation of the intermetallic compound IMC—must be completed within 0.8 to 1.2 seconds. If the immersion angle deviates by more than 3° or the speed fluctuates beyond ±15 mm/s, it will cause one-sided wetting lag, an increase in void rate at the pin root, and even uneven solder volume across an entire row of pins.

Manual Dip Soldering Pots Are Suitable for Rapid Verification of Small-Batch, Multi-Variety Production

The JJY JY-300B manual dip soldering pot plays a key role in the trial production phase. Its independently temperature-controlled 300 mm × 150 mm solder bath can maintain a constant temperature of 255 ± 2°C. Paired with a 0–5 second adjustable timer and a pneumatic pressing mechanism, it enables operators to complete pin dip soldering verification for DIP-packaged relays, DIP switches, and dual in-line package ICs without changing fixtures. It is especially suited to the need of modifying boards and producing solder joint cross-sections on the same day when customers send samples, avoiding delays to prototyping milestones caused by waiting for wave soldering furnace scheduling.

Wave Soldering Furnace Dip Soldering Parameters Must Match Substrate Thickness and Component Density

When the JJY WAVE-550 runs on mass production lines, we always set the solder wave height to 1.8 mm above the top of the conveyor chain claws, which corresponds to the standard configuration for 1.6 mm thick PCBs. For 0.8 mm thin boards, the height must be reduced by 0.4 mm synchronously and bottom nitrogen flotation must be enabled; otherwise, board warpage, pin solder dragging, or backside solder adhesion are likely to occur. For high-density boards with pin spacing less than 2.54 mm, the dip soldering speed must be reduced from 1.2 m/min to 0.9 m/min, and a 0.3-second delayed solder blow must be added at the wave exit section; otherwise, the bridging probability will surge from the conventional 0.03% to above 0.27%.

The State of the Molten Solder Surface Directly Determines Solder Joint Formation Quality

Every day before startup, the floating dross on the solder surface must be scraped off with a stainless steel scraper; otherwise, oxide inclusions will cause dull solder joints, solder spikes, and a wetting angle greater than 90°. Once the copper content in the solder exceeds 0.35 wt%, the machine must be shut down for solder replacement, because the copper-tin intermetallic compound Cu6Sn5 will accumulate at the wave exit, causing continuous solder balls at the pin root. This type of defect cannot be identified during AOI inspection, but it will cause batch open-circuit failures during aging testing.

The Cooling Rhythm After Pin Dip Soldering Also Cannot Be Ignored

A PCB that has just left the solder bath cannot immediately enter a strong air cooling zone; it must first pass through a 3–5 second natural heat dissipation transition section. Otherwise, sudden thermal stress changes will cause microcracks in the body of QFP-type devices, while accelerating embrittlement and peeling of the PCB solder mask. We have tested on JJY equipment and found that when the cooling air speed is suddenly increased from 1.5 m/s to 4.2 m/s, the pad peeling rate of PCBs with OSP surface treatment rises by 17 percentage points. Therefore, all cooling sections are equipped with a stepped air speed attenuation curve.