PCB Solder Splashing: Causes, Solutions and Wave Soldering Process Optimization

Overview

PCB solder splashing can lead to incomplete solder joints, increased manual rework, and interruptions in electronics manufacturing. In a recent customer support case, double-sided PCBs experienced recurring soldering defects even after being baked at approximately 110°C for two hours.

Shenzhen Yifang Electronics worked with the customer to investigate possible causes, including moisture, through-hole plating, copper thickness, soldering temperature, and conveyor speed. Based on previous experience resolving similar issues, our engineering team recommended reviewing and optimizing the soldering process parameters.

This case explains the troubleshooting approach, the importance of temperature control, and how PCB manufacturers and assembly teams can collaborate to improve production reliability.

1. Customer Background: Recurring Defects During PCB Assembly

The customer was assembling double-sided FR-4 printed circuit boards intended for high-current electrical applications.

During production, operators observed repeated soldering problems, including solder splashing, incomplete through-hole solder joints, and visible solder cavities.

Earlier production batches had experienced similar problems on a smaller scale. However, the latest batch showed more frequent defects, resulting in additional manual inspection and rework.

The customer's main concern was identifying the cause before continuing production.

2. The Problem: Why Did PCB Baking Fail to Eliminate Solder Splashing?

Initially, moisture absorption was suspected as a potential cause.

The customer attempted to reduce this risk by baking the PCBs under the following conditions:

Production operators also reported that defects occurred in both larger and smaller through-holes.

These observations indicated that moisture and hole dimensions alone might not fully explain the soldering difficulties.

Further investigation was therefore required.

3. Technical Investigation: Potential Causes of PCB Solder Splashing

Several factors can contribute to soldering defects during through-hole assembly.

3.1 PCB Moisture and Storage Conditions

Moisture trapped within PCB materials may expand during heating and contribute to soldering abnormalities.

However, the effectiveness of baking depends on PCB construction, material specifications, storage conditions, and the baking process itself.

Baking does not automatically eliminate all possible soldering defects.

3.2 Through-Hole Plating and PCB Structure

Cross-section inspection can help engineers evaluate plated through-hole structures, copper plating integrity, and possible gaps between conductive and insulating materials.

In this case, the customer supplied cross-section findings that raised concerns about gaps near the plated hole structure.

Such observations require further evaluation. A visible gap alone does not establish the root cause of solder splashing.

3.3 Soldering Temperature Profile

An unsuitable soldering temperature profile may result in insufficient heating, inconsistent solder wetting, or other solder joint defects.

The correct profile depends on factors including PCB thickness, copper distribution, component thermal characteristics, flux, and solder alloy.

3.4 Conveyor Speed and Solder Contact Time

Conveyor speed influences the board's travel through the heating and soldering stages.

Improper settings may affect solder joint formation and process consistency.

Conveyor speed and actual solder contact time must be evaluated together, rather than treating them as identical measurements.

4. Our Recommended Solution: Temperature and Conveyor Speed Optimization

Based on our previous experience with similar soldering problems, Shenzhen Yifang Electronics recommended reviewing the customer's soldering equipment parameters.

The proposed troubleshooting approach focused on three areas.

Step 1: Review Soldering Equipment Settings

Collect the existing temperature profile, conveyor speed, equipment model, and solder material specifications.

Step 2: Optimize Heating Conditions

Evaluate whether the PCB receives suitable preheating and soldering temperatures based on its construction and assembly requirements.

Step 3: Conduct Controlled Production Trials

Adjust suitable process parameters within validated equipment and material limits, then compare the resulting solder joint quality.

Each trial should record operating conditions, defect locations, and inspection results to determine whether the adjustments produce a repeatable improvement.

Our previous experience indicates that optimizing temperature profiles and conveyor speed can noticeably improve certain soldering problems.

However, each customer's process requires independent validation.

5. Why Process Optimization Matters

Temperature and conveyor speed optimization can help improve manufacturing consistency when inappropriate process settings contribute to soldering defects.

Potential benefits include:

• More consistent solder joint formation

• Reduced solder splashing associated with process conditions

• Less manual inspection and soldering rework

• Improved assembly process stability

In this case, the recommended parameter adjustments provided a practical direction for further troubleshooting.

PCB structural concerns and copper thickness discrepancies also require independent examination, even when soldering performance improves.

A complete quality investigation should distinguish verified findings from possible contributing factors.

6. Key Takeaways for Electronics Manufacturers

1. Baking is not a universal solution.

If soldering defects continue after baking, other manufacturing conditions should be reviewed.

2. PCB construction and assembly parameters must be evaluated together.

Through-hole design, copper thickness, soldering temperature, flux, and conveyor speed can all influence soldering performance.

3. Process adjustments require measurable validation.

Comparing defect rates and solder joint quality under controlled conditions helps determine whether improvements are effective.

4. Supplier collaboration helps solve production challenges.

PCB manufacturers and assembly teams can work together to identify problems, evaluate technical evidence, and develop practical solutions.

7. About Shenzhen Yifang Electronics

Shenzhen Yifang Electronics Co., Ltd. is a China-based PCB manufacturer with over 20 years of industry experience.

We provide one-stop PCB and PCBA manufacturing services, including:

• Double-sided and multilayer PCB fabrication

• PCB prototyping and mass production

• Component sourcing and PCB assembly

• Engineering communication and production support

• PCB quality inspection and manufacturing improvement

We believe reliable PCB manufacturing extends beyond delivering finished circuit boards.

Our goal is to help customers achieve consistent manufacturing quality through technical support, communication, and continuous improvement.

Need help with your next PCB or PCBA project?

Contact Shenzhen Yifang Electronics to discuss your manufacturing requirements.

Website: https://yifangpcba.leapzii.com/

Email: dexter@yfpcb.cn

WhatsApp: +86 13636690372