Through Hole Assembly Services for Industrial Control Applications

Through hole assembly (THT) is a foundational electronics manufacturing technique where components with leads are inserted through drilled holes in a printed circuit board (PCB), followed by soldering to create robust mechanical and electrical connections. For industrial control systems—where reliability, durability, and resistance to harsh environments are non-negotiable—THT remains indispensable. Its ability to withstand vibration, temperature fluctuations, and high power loads makes it a preferred choice for critical applications in aerospace, automotive, and factory automation. LTPCBA, a leader in electronics manufacturing, delivers precision-driven through hole assembly services tailored to the stringent demands of industrial control.

Key Insights

• THT excels in harsh environments: Its solder joints form mechanical bonds that resist vibration and thermal stress—critical for industrial control systems operating in factories, power plants, and aerospace settings.
• Power and durability are hallmarks: Through hole components handle higher current and voltage than surface-mount devices (SMDs), making them ideal for power regulators, transformers, and connectors in industrial equipment.
• LTPCBA’s expertise ensures quality: With ISO 9001, IATF 16949, and UL certifications, LTPCBA delivers THT assemblies with a 99.5% pass rate, supported by 24/7 technical support and rigorous testing.

What Is Through Hole Assembly?

Through hole assembly involves mounting electronic components by inserting their leads into pre-drilled holes in a PCB, then soldering the leads to copper pads on the opposite side. This creates both electrical conductivity and mechanical stability. Two primary hole types facilitate this process:

• Plated Through Holes (PTH): Coated with a conductive material (e.g., copper) to enable electrical connections between PCB layers—essential for multi-layer boards in complex control systems.
• Non-Plated Through Holes (NPTH): Uncoated holes used for mechanical mounting (e.g., securing brackets) or single-sided components where layer-to-layer conductivity is unnecessary.

Components used in THT include:

• Passive components: Resistors, capacitors, and inductors with axial leads (extending from opposite ends) or radial leads (extending from the same side for space efficiency).
• Active components: Integrated circuits (ICs) in dual in-line packages (DIPs), transistors, and relays—often larger and heavier, requiring the structural support THT provides.

Technical Standards and Specifications

THT adheres to strict industry standards to ensure consistency and reliability, as outlined in IPC-A-610 and J-STD-001. Key parameters include:

Aspect	Specification
Drill Hole Size	Minimum hole diameter = Maximum lead diameter + 0.15–0.25mm (varies by density class: A, B, C).
Annular Ring	Minimum 0.1mm width to ensure strong solder joints and prevent pad lifting.
Pad Diameter	Calculated as: Hole size + 2×(annular ring width) + 0.4–0.6mm (clearance, depending on density).
Solder Mask Relief	4 mils (0.1mm) between solder mask and pads to avoid solder bridging.
Solder Fill	100% fill preferred; 75% acceptable for IPC Class 2 (commercial) and 3 (high-reliability) applications.
Lead Processing	Leads inserted from top to bottom; bent 0.5–1mm above solder joints to enhance mechanical strength.

Key Benefits of Through Hole Assembly for Industrial Control

THT offers unique advantages that make it irreplaceable in industrial environments:

1. Superior Mechanical Strength

Solder joints in THT form a physical bond between component leads and PCB pads, resisting vibration and shock—critical for factory floors, where equipment often operates amid constant motion. Tests show THT joints withstand 3x more vibrational stress (10–2000Hz) than surface-mount joints, reducing failure rates in industrial robots and motor controllers.

2. High Power Handling

Through hole components, with their thicker leads and larger solder joints, efficiently dissipate heat and carry higher currents (up to 100A in power connectors) compared to SMDs. This makes THT ideal for power supplies, motor drivers, and variable frequency drives (VFDs) in industrial control systems.

3. Ease of Inspection and Repair

THT solder joints are visible to the naked eye, simplifying inspection for defects like cold joints or bridging. Technicians can replace components manually with basic tools—reducing downtime in critical systems. For example, a faulty relay in a factory control panel can be swapped out in minutes, whereas replacing an SMD relay requires specialized rework stations.

4. Compatibility with Large Components

Heavy components like transformers, terminal blocks, and heat sinks require the structural support of THT. Their weight (often >50g) would risk detachment from SMT pads, but THT’s through-hole mounting distributes stress across the PCB.

Why THT Matters in Industrial Control Applications

Industrial control systems demand electronics that operate flawlessly in extreme conditions. THT meets these demands through:

1. Reliability Under Continuous Operation

Factory control systems, power grids, and aerospace equipment run 24/7. THT’s robust joints minimize downtime—critical when even a 1-hour outage can cost industrial facilities $100,000+. Field data shows THT assemblies in industrial controllers have a mean time between failures (MTBF) of 100,000+ hours, compared to 60,000+ hours for SMT-dominant assemblies.

2. Resistance to Harsh Environments

Industrial settings expose electronics to:

• Temperature extremes: -40°C to 85°C in outdoor or unconditioned spaces.
• Moisture and dust: IP65/IP67-rated enclosures require sealed assemblies, where THT’s solder joints resist corrosion better than SMT.
• Chemical exposure: Oils, solvents, and industrial gases can degrade SMT solder paste residues, but THT’s robust solder joints (protected by conformal coatings) hold up longer.

THT assemblies undergo rigorous testing, including thermal cycling (-40°C to 125°C, 1000 cycles), vibration testing (10–2000Hz), and ingress protection (IP) testing to ensure compliance with IEC 60529.

Through Hole Assembly vs. Surface Mount Technology (SMT)

While SMT dominates in consumer electronics, THT remains critical for industrial control. The table below compares their key differences:

Factor	Through Hole Assembly (THT)	Surface Mount Technology (SMT)
Component Size	Larger (leaded); suitable for heavy/powerful parts (e.g., transformers).	Smaller (SMDs); ideal for compact, low-power devices (e.g., sensors).
Mechanical Strength	High; resists vibration and shock (critical for industrial use).	Lower; SMD joints may crack under stress.
Power Handling	Excellent (handles >10A); suitable for power regulators and motor drivers.	Limited (typically <5A); better for low-power, high-speed circuits.
Manufacturing Speed	Slower; may require manual insertion for large components.	Faster; fully automated for high-volume, small components.
Repair Ease	Easy; components replaced with basic tools.	Difficult; requires reflow ovens or hot-air stations.
Cost (Setup)	Lower (10,000–50,000 for equipment).	Higher (50,000–500,000+ for pick-and-place machines).
Density	Lower (10–20 components/sq. inch).	Higher (up to 100 components/sq. inch).

Industrial Use Cases Favoring THT

• Aerospace: Avionics control systems require THT for vibration resistance during flight.
• Automotive: Engine control modules (ECMs) use THT for high-temperature and power handling.
• Factory Automation: Motor controllers, PLCs (Programmable Logic Controllers), and power supplies rely on THT for durability.
• Energy: Smart grid equipment and power distribution units use THT for high-current connections.

LTPCBA’s Through Hole Assembly Services

LTPCBA specializes in THT solutions for industrial control, combining precision, speed, and compliance to meet the sector’s toughest demands.

Service Capabilities

• Full Turnkey Solutions: From PCB design reviews to final assembly, including component sourcing, insertion, soldering, and testing.
• Handling Diverse Components: Expertise with axial/radial leads, DIP ICs, terminal blocks, and heavy components (up to 500g).
• Advanced Testing: In-circuit testing (ICT), functional testing (FCT), and environmental testing (thermal cycling, vibration) to validate performance in real-world conditions.
• Rapid Turnaround: Quotes within 2–3 days, prototypes in 5–7 days, and high-volume production with 98% on-time delivery.

Quality Standards and Certifications

LTPCBA’s commitment to quality is validated by industry certifications:

Certification	Purpose
ISO 9001:2015	Ensures consistent quality management systems and customer satisfaction.
IATF 16949	Meets automotive industry requirements for defect prevention.
ISO 13485:2016	Complies with medical device standards (relevant for industrial healthcare equipment).
UL Certification	Validates safety and reliability for electrical components.

LTPCBA also adheres to IPC-A-610 (Class 3 for high-reliability) and RoHS compliance, ensuring assemblies are free from hazardous substances.

Performance Metrics

• First-Pass Yield: >99% (minimizing rework and delays).
• Defect Detection: 99% of manufacturing defects identified via AOI (Automated Optical Inspection) and X-ray.
• Technical Support: 12 dedicated engineers providing 24/7 assistance for urgent issues.

Choosing the Right Through Hole Assembly Provider

Selecting a THT partner for industrial control requires evaluating:

1. Certifications: Ensure compliance with IPC, ISO, and industry-specific standards (e.g., IATF 16949 for automotive).
2. Testing Capabilities: Look for in-house ICT, FCT, and environmental testing to validate performance.
3. Component Sourcing: Verify traceability to avoid counterfeit parts—critical for industrial reliability.
4. Turnaround Time: Fast quotes and on-time delivery to meet project deadlines.
5. Repair and Rework Support: Access to skilled technicians for post-assembly fixes.

Why Choose LTPCBA?

LTPCBA’s industrial-focused THT services stand out through:

• Rigorous quality control: 99.5% pass rate and 100% traceability for every component.
• Industrial expertise: Deep understanding of harsh environment requirements (vibration, temperature, ingress).
• Scalability: From prototypes to high-volume production (10,000+ units/month).
• Customer-centric support: 24/7 technical help and proactive communication throughout the project lifecycle.

FAQ

Q: What components are best suited for through hole assembly?

A: Heavy, high-power components like transformers, terminal blocks, relays, and DIP ICs—common in industrial control systems.

Q: How does LTPCBA ensure THT reliability in harsh environments?

A: Assemblies undergo thermal cycling, vibration testing, and IP testing. Conformal coatings (e.g., urethane) protect against moisture and chemicals.

Q: Can LTPCBA handle mixed technology assemblies (THT + SMT)?

A: Yes. LTPCBA integrates THT and SMT for complex boards, ensuring compatibility and reliability in industrial controls.

Through hole assembly remains a cornerstone of industrial control electronics, offering unmatched durability and power handling. LTPCBA’s precision-driven services, backed by certifications and technical expertise, make it the ideal partner for critical industrial applications.