SMT Troubleshooting

Introduction

Stable PCB transfer between machines is critical to maintaining a smooth and efficient SMT production line.
When PCB transfer failures occur between machines—such as between a printer, reflow oven, AOI, or conveyor—it often leads to line blocking, unplanned downtime, and reduced output.

This article explains the root causes, typical symptoms, and proven solutions for PCB transfer failures in automated SMT lines.

Common Symptoms of PCB Transfer Failures

PCB transfer issues usually present one or more of the following symptoms:

• PCB stops at the end of an upstream machine

• Downstream machine does not accept incoming PCB

• Conveyor runs but PCB does not move forward

• Frequent SMT line blocking alarms

• Inconsistent transfer behavior between different machine brands

Recognizing these symptoms early helps prevent further production losses.

Main Causes of PCB Transfer Failures

1. SMEMA Communication Issues

SMEMA is widely used for communication between SMT machines.
Common problems include:

• Incorrect SMEMA cable wiring

• Signal polarity mismatch

• Incompatible SMEMA implementation between brands

• Loose or damaged connectors

Even minor signal inconsistencies can stop PCB transfer.

2. Conveyor Height and Width Mismatch

Improper mechanical alignment between machines can cause:

• PCB edge collision

• PCB tilting or jamming

• Sensors failing to detect PCB presence

Height and width mismatches are especially common after line reconfiguration.

3. Sensor Misalignment or Failure

Transfer sensors may fail due to:

• Contamination from flux or dust

• Mechanical vibration

• Aging or damaged sensor components

Faulty sensors prevent machines from recognizing PCB readiness.

4. Software or Parameter Configuration Errors

Incorrect settings such as:

• Board width parameters

• Conveyor speed mismatch

• Incorrect transfer mode selection

can interrupt normal PCB handover between machines.

5. Mixed Brand Compatibility Issues

SMT lines using machines from different manufacturers may experience:

• Different SMEMA timing logic

• Unique safety interlocks

• Brand-specific handshake protocols

These differences often require additional adjustment or interface solutions.

Step-by-Step Troubleshooting Guide

Step 1: Check SMEMA Signal Status
Verify SMEMA cables, signal polarity, and handshake timing.

Step 2: Inspect Conveyor Alignment
Ensure conveyor height and width match across all connected machines.

Step 3: Test Transfer Sensors
Clean sensors and verify correct detection logic.

Step 4: Review Machine Parameters
Confirm PCB size, speed, and transfer mode settings.

Step 5: Perform Single Machine Test
Test upstream and downstream machines independently to isolate the issue.

Preventive Measures for Stable PCB Transfer

• Standardize conveyor height across the SMT line

• Use high-quality SMEMA cables and connectors

• Implement regular sensor cleaning schedules

• Validate parameters after line changes

• Document transfer settings for each product type

Preventive actions reduce downtime and increase overall line efficiency.

When to Consider Automation Solutions

If PCB transfer failures occur frequently, consider:

• Smart conveyors with adaptive height adjustment

• SMEMA / automation interface upgrades

• Line balancing and layout redesign

👉 Explore our SMEMA / Automation Solutions for stable PCB flow across your SMT line.

Conclusion

PCB transfer failures between machines are usually caused by communication, mechanical alignment, or configuration issues rather than equipment failure.
With systematic troubleshooting and proper preventive measures, most transfer problems can be resolved quickly and permanently.

Internal Linking Suggestions

• SMT Line Blocking Caused by Unstable PCB Transfer

• SMEMA Signal Not Working Between Different SMT Machine Brands

• SMT Line Layout Design

• SMT Process Optimization

Thomao Engineering Insight

A smooth SMT line is not about faster machines,
but about reliable communication and stable PCB flow.