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THT PCB Assembly
THT (Through-Hole Technology), also known as through-hole insertion technology, is an assembly process where component leads are inserted into pre-drilled holes on a PCB, followed by soldering via wave soldering, selective soldering, or manual soldering. It is often used in combination with SMT.
- High current-carrying capacity
- High mechanical strength
- High reliability
- Compatible with hybrid assembly
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Our THT PCB Assembly
Zintilon Technology is committed to providing advanced THT PCB assembly services to global users, supporting THT PCB assembly from product R&D prototype to small-batch production. From printing to assembly, we ensure to deliver efficient and reliable THT PCB assembly solutions for you.
THT PCB Assembly Materials
| Category | Typical Specifications | Key Indicators | Remarks |
|---|---|---|---|
| Component Leads | Tin-plated copper alloy (C1100, C5191) | Elongation ≥ 20%, solderability at 245℃ | 0.8–1.2 mm diameter for high current applications |
| Solder | SnCu0.7 (lead-free wave soldering) | Melting point 227℃, silver content 0%, low cost | Slightly lower fluidity compared to SAC305 |
| Flux | Alcohol-based no-clean (ROL0) | Halogen content 0 ppm, SIR > 1×10¹² Ω | Foam spraying, solid content 2–3% |
| Solder Mask/Hole Plugging | High-temperature resistant solder mask ink | Withstands 288℃ for 10s, no bubbles | Prevents solder from adhering to non-pad areas during wave soldering |
| PCB Substrate | High Tg FR-4 (170℃) | Common thickness 1.6–2.4 mm | Thick boards resist warpage, suitable for heavy components |
| Gaskets/Bushings | Mica/silicone gaskets | Voltage resistance 3 kV, thermal conductivity ≥ 1 W/m·K | Insulation between power devices and heat sinks |
THT PCB Assembly Surface Finishes
| Process | Thickness | Advantages in THT | Limitations |
|---|---|---|---|
| HAL-LF (Hot Air Leveling) | SnCu 1–2 µm | Low cost, good hole wall wetting, repairable | Poor flatness, not recommended for ≤0.5 mm pitch |
| ENIG | Ni 3–5 µm + Au 0.05 µm | Complete hole wall coverage, wire bondable | Risk of black nickel, cost increased by 15% |
| Immersion Tin (ImSn) | 0.8–1.2 µm | Flat, compatible with any solder | Storage life 6 months, low-temperature tin immersion solution required for thick boards |
| OSP | 0.2–0.5 µm | Minimum skin effect loss, suitable for RF boards | Not resistant to multiple wave soldering, limited to single-sided one-time soldering |
| Electroplated Hard Gold (Gold Fingers) | Ni 3–5 µm + Au 0.5–1.5 µm | Wear-resistant, >10,000 insertion cycles | Only for edge connectors, not for solder joints |
Why Choose Our
THT PCB Assembly?
One-on-One Quotation
Simply upload your .gbr file to receive a quotation feedback within 24 hours. Our professional engineers will analyze your design to avoid misunderstandings, communicate with you, and provide a reasonable price.
High-Quality Assembled
We maintain a rigorous and responsible attitude toward materials, processes, surface treatments, A.O.I (Automated Optical Inspection), and flying probe testing, ensuring consistent high quality from prototype production to mass manufacturing.
Fast Delivery
Equipped with advanced machinery and a professional quotation team to ensure fast delivery. We prioritize orders based on requirements and complexity. Cutomized delivery sulution is also available.
Real-Time Communication
For your benefit, we provide full-cycle technical support for each customer from quotation to delivery. We will respond quickly to any questions until you confirm satisfactory THT PCB assembly.
THT PCB Assembly Standards
Zintilon ensures quality through our THT PCB assembly design and manufacturing standards from design to delivery by follow up IPC standards (IPC-2221C, IPC-6012E) to ensure manufacturability and reliability.
Item
Spec
Hole diameter = lead diameter + 0.15–0.30 mm
Round leads: +0.20 mm; rectangular leads (diagonal): +0.25 mm; minimum 0.15 mm margin to ensure solder climbing.
Pad annular ring width ≥ 0.20 mm (8 mil)
Prevent "annular ring breakage" and exposure of the substrate during HAL; Class 3 high reliability requires ≥ 0.25 mm.
Copper plating thickness ≥ 25 µm (1 mil)
For power pins with current > 2 A, increase hole copper thickness to 35–50 µm to reduce temperature rise by 10 K.
Isolation ring ≥ 0.25 mm between hole wall and inner layer power/ground copper foil in multi-layer boards
Avoid cold soldering caused by excessive heat dissipation from inner layer copper during wave soldering; meet 500 V voltage breakdown.
Avoidance of wave soldering "shadow effect"
For tall components (electrolytic capacitors, inductors) with height > 15 mm, small components must be placed in the front row and tall components in the back row with spacing ≥ 1.5 mm; or use selective wave soldering fixtures.
Hole Plugging/Windowing Rules
For areas requiring secondary SMT, solder mask windowing on the wave soldering side extends 0.05 mm beyond the pad to prevent solder balls; Fully plug non-welded mechanical holes with green oil to avoid moisture absorption.
High-Current Parallel Multi-Pins
Each pin carries ≤ 1 A current; center-to-center distance between pins ≥ 2.54 mm to facilitate solder filling; add 2 oz copper foil in parallel on the top layer.
Thermal Shock and CTE Matching
Thick copper (≥ 2 oz) + high Tg FR-4 (170℃) + 35 µm hole copper, no cracks after 1000 thermal cycles of -40~+125℃; For aluminum substrate THT, copper plating must be performed before HAL to prevent Al-Sn alloy embrittlement.
THT PCB Assembly Guidelines
Zintilon ensures quality through our THT PCB assembly design and manufacturing standards from design to delivery by follow up IPC standards (IPC-2221C, IPC-6012E) to ensure manufacturability and reliability.
Item
SubItem
Value/Requirement
Source/Remarks
Hole and Pad Specifications
SubItem Hole Diameter
Value/Requirement D+0.20~0.30 mm (D = lead diameter)
Source/Remarks Minimum 0.6 mm for automatic insertion; otherwise, drill breakage is likely during punching
SubItem Pad Annular Ring Width
Value/Requirement ≥ 0.20 mm (Class 2) (0.40 mm for aerospace)
Source/Remarks Breakage rate < 50 ppm
SubItem Pad Diameter
Value/Requirement D=(2.5~3)d when hole diameter ≤0.4 mm; D=(1.5~2)d when hole diameter >2 mm
Source/Remarks Ensure peel strength ≥ 1.5 N/mm
SubItem Annular Ring to Board Edge
Value/Requirement ≥ 1.0 mm
Source/Remarks Prevent edge chipping during milling
Automatic Insertion Layout
SubItem PCB Dimensions
Value/Requirement 150–330 mm × 50–250 mm × 1.60±0.10 mm
Source/Remarks Maximum clamping range of automatic insertion machines
SubItem Locating Holes
Value/Requirement Ø4 +0.05 mm, 5 mm from both sides
Source/Remarks Repeat positioning accuracy ±0.05 mm
SubItem Board Conveyor Edge No-Mount Area
Value/Requirement No components within 5 mm of top/bottom edges
Source/Remarks Prevent component damage by clamping jaws
SubItem Axial Component Span
Value/Requirement 10 mm, 12.5 mm, 15 mm, 17.5 mm (preferably integer multiples of 2.54 mm)
Source/Remarks Matching the pitch of automatic insertion machine sprockets
SubItem Radial Component Density
Value/Requirement Clearance of 0.2 mm from the radius of inserted components
Source/Remarks Avoid collision during bending
Wave Soldering Manufacturability (DFM)
SubItem Component Height
Value/Requirement ≤ 15 mm (use post-wave soldering or selective soldering if >15 mm)
Source/Remarks Prevent cold soldering caused by excessive heat dissipation
SubItem Adjacent Pad Spacing
Value/Requirement ≥ 0.8 mm (lead-free) ≥ 1.0 mm (tin-copper)
Source/Remarks Bridging rate < 100 ppm
SubItem Large Copper Foil Windowing
Value/Requirement Grid or 0.3 mm wide windows with 0.8 mm spacing
Source/Remarks Prevent cold soldering caused by excessive heat dissipation
SubItem Lead Protrusion from Board Bottom
Value/Requirement 0.8–1.2 mm (Class 2)
Source/Remarks Excessively long leads are prone to bridging; excessively short leads lack meniscus (IPC-A-610 G)
Thermal-Mechanical Reliability
SubItem Hole Copper Thickness
Value/Requirement ≥ 25 µm (1 mil) (Class 2) ≥ 35 µm (automotive grade)
Source/Remarks Temperature rise reduced by 10 K when current > 2 A
SubItem Copper Plating Uniformity
Value/Requirement ±5 µm (Cpk ≥ 1.33)
Source/Remarks Prevent thermal cycle cracks
SubItem Thermal Shock Cycles
Value/Requirement -40 ↔ +125 ℃, 1000 cycles, hole resistance change ≤ 10%
Source/Remarks Meeting IPC-TM-650 2.6.7
SubItem Power Device Thermal Relief
Value/Requirement Cross-shaped bridges with 0.3–0.4 mm width
Source/Remarks Reduce thermal stress and avoid pad lifting
High-Speed/High-Density Supplements
SubItem Signal THT Vias
Value/Requirement Hole diameter 0.3 mm, pad 0.6 mm, isolation area 0.9 mm
Source/Remarks Reduce parasitic capacitance
SubItem Power/Ground Vias
Value/Requirement Hole diameter 0.5–0.7 mm, low impedance
Source/Remarks Can withstand 5 A transient current
SubItem Signal Cross-Zone Prohibition
Value/Requirement High-speed lines should not cross THT partition zones as much as possible
Source/Remarks Reduce reflection
Our Custom THT PCB Assembly for Various Industrial Applications
Though no longer the go-to for high-density designs, Through-Hole Technology (THT) assembly remains unmatched where “high power, high stress, and high reliability” rule the roost. characteristics: "high mechanical strength, resistance to vibration and impact, excellent heat dissipation, and strong high-current carrying capacity," making it the "robust connection hub" for electronic equipment, covering key application scenarios from industrial control to special equipment.
THT PCB Assembly FAQs
We cooperate with multiple certification bodies and can handle CE certification, FCC certification, RoHS certification, FDA certification, etc.
We have a highly professional engineering team with extensive design experience in fields such as industrial control, consumer electronics, new energy, and medical devices.
Throughout the product development process, we confirm each step with the client. If the project design includes sample testing, we will conduct electrical performance testing, functional testing, performance testing, and reliability testing to ensure design quality.
Got any more questions?
Ultimate Guide
to THT PCB Assembly
to THT PCB Assembly
THT PCB Assembly Service
Various and Robust THT PCB Assembly Services
Prototype
Prototyping
From Gerber files to circuit boards, our professional engineering team provides you with the highest quality THT PCB assembly services. We meticulously control every detail of the process, including drilling, electroplating, and AOI, ensuring precise control over trace spacing, thickness, and panel dimensions. We are committed to providing you with the most reliable PCB assembly.
- Complete production line
- Professional engineering support
- 10+ years‘ manufacturing experience
Production
Production
We have our own production lines and a robust manufacturing network. From PCB design, engineering, and manufacturing, we have sufficient capacity to provide you with professional and fast delivery services, whether for small or large batches. We spare no effort in providing consistent mass production services for your products.
- Strong supply chain team
- Competitive pricing
- One-stop service from design to delivery
Let’s Build Something Great, Together
