Double-sided through-hole PCB boards

I. Product Overview

UGPCB Double-Sided Through-Hole PCB Board is a high-performance 2-layer rigid printed circuit board built on an FR-4 glass-epoxy substrate using plated through-hole (PTH) technology. The board measures 86.9 × 73.58 mm with a thickness of 1.0 mm, copper foil thickness of 1/1 OZ (35 μm on both outer and inner layers), and a lead-free hot air solder leveling (HASL) surface finish. The solder mask is green, and the silkscreen legend is white.

A double-sided through-hole PCB (double-sided printed circuit board) features conductive circuitry on both sides of the insulating substrate, with plated through-holes enabling electrical interconnection between the two layers. Compared to single-sided PCBs, double-sided PCBs offer 60%–80% higher routing density and support more complex circuit designs. UGPCB, backed by ISO-certified quality systems and IPC-compliant manufacturing processes, delivers high-quality double-sided through-hole PCBs and turnkey PCBA services to electronics manufacturers worldwide.

II. Product Definition and Technical Specifications

Per IPC-6012F Qualification and Performance Specification for Rigid Printed Boards (published September 2023), the double-sided through-hole PCB is classified as a rigid printed board with plated through-holes (Type 2). Its core feature is the electrical connection between conductors on both sides through copper-plated hole walls. UGPCB manufactures this product in full compliance with IPC-6012F and meets Class 2 performance requirements (dedicated service electronic equipment).

Key Specifications:

III. Design Guidelines

3.1 Substrate Material Selection — Engineering Value of FR-4

FR-4 is a flame-retardant grade designation established by the National Electrical Manufacturers Association (NEMA). The letters “FR” stand for flame-retardant, and the number “4” denotes an epoxy resin system reinforced with woven glass fabric. Per IPC-4101 Specification for Base Materials for Rigid and Multilayer Printed Boards, FR-4 Grade A1 represents the core performance tier with optimal mechanical strength, electrical properties, and long-term reliability.

Key Performance Indicators of FR-4 (Source: IPC-4101 and industry standards):

• Glass Transition Temperature (Tg): 130–140°C (standard FR-4)

• Dielectric Constant (Dk) @ 1 GHz: 4.2–4.5

• Dissipation Factor (Df) @ 1 GHz: ≤ 0.020

• Flammability Rating: UL 94 V-0

• Water Absorption (24 hours): ≤ 0.10%

FR-4 remains the predominant substrate material in the PCB industry because it offers an outstanding balance of mechanical strength, electrical insulation, dimensional stability, and processability.

3.2 Circuit Design Standards per IPC-2221

Per IPC-2221 Generic Standard on Printed Board Design, conductor width design must account for current-carrying capacity, temperature rise, and copper thickness. The IPC-2221 current-carrying capacity formula is:

I = k · ΔT^0.44 · A^0.725

Where:

• I = Maximum current-carrying capacity (A)

• k = Empirical constant (0.048 for external layers, 0.024 for internal layers)

• ΔT = Allowable temperature rise (°C)

• A = Conductor cross-sectional area (mil²), where A = W × T

UGPCB’s product features a line width of 0.32 mm (approx. 12.6 mil), line spacing of 0.37 mm (approx. 14.6 mil), and copper thickness of 1 OZ (35 μm). For an external layer trace with a 10°C temperature rise:

A = 0.32 mm × 0.035 mm = 0.0112 mm² ≈ 17.36 mil²

I = 0.048 × 10^0.44 × 17.36^0.725 ≈ 0.048 × 2.75 × 7.82 ≈ 1.03 A

This conductor width supports approximately 1 A of current, meeting the power and signal transmission needs of most consumer electronics and industrial control equipment. IPC-2221 recommends limiting the maximum temperature rise to 10°C or 20°C to preserve PCB service life.

3.3 Hole Diameter and Aspect Ratio Design

The aspect ratio of a through-hole is a critical metric for evaluating drilling and hole metallization difficulty. The formula is:

Aspect Ratio = Board Thickness / Drilled Hole Diameter

For UGPCB’s product with 1.0 mm board thickness and 0.236 mm minimum hole diameter:

Aspect Ratio = 1.0 / 0.236 ≈ 4.24:1

This aspect ratio is well below the industry-recommended upper limit of 10:1 and the conservative design threshold of 8:1. It indicates low difficulty in drilling and metallization, high yield rates, controlled costs, and assured through-hole reliability.

3.4 Land Pattern Design Reference

Per IPC-7351 Generic Requirements for Surface Mount Design and Land Pattern Standard, land pattern design must ensure adequate solder fillet formation and meet solderability, inspectability, and reworkability requirements. For through-hole components, land diameter is typically recommended at 1.8–2.2 times the hole diameter to ensure sufficient annular ring width.

IV. Operating Principle

The double-sided through-hole PCB operates on three core technologies:

1. Double-Sided Routing — Conductive circuit patterns are etched on both the top and bottom surfaces of the FR-4 insulating substrate, allowing component placement on both sides. This significantly increases circuit density and design flexibility.

2. Plated Through-Hole (PTH) Interconnection — After drilling, electroless copper deposition and electrolytic copper plating build up a conductive layer on the hole walls. This creates low-resistance, highly reliable electrical connections between the top and bottom layers. Per IPC-6012F Class 2, the minimum average plated copper thickness on hole walls must be ≥ 20 μm.

3. Component Assembly and Soldering — Components are mounted through hole (THT) or surface mount (SMT) techniques and electrically connected via reflow or wave soldering, producing a fully functional PCBA (Printed Circuit Board Assembly) module.

V. Product Classification

Per the IPC-6012F classification system for rigid printed boards, UGPCB’s product is classified as follows:

By application domain, this product falls into the General Industrial Grade Double-Sided PCB category, suitable for consumer electronics, industrial controls, communication equipment, power adapters, and other medium-reliability applications.

VI. Material Composition

6.1 Substrate — FR-4 Copper-Clad Laminate

FR-4 is a glass-reinforced epoxy laminate composed of electronic-grade woven glass fabric as reinforcement and epoxy resin as the binder, consolidated under high temperature and pressure. Its UL 94 V-0 flammability rating means that in the vertical burn test, the material self-extinguishes within 10 seconds after each of two 10-second flame applications, with no flaming drips that ignite cotton.

6.2 Copper Foil — 1/1 OZ

One ounce (1 OZ) of copper foil has a thickness of 35 μm (1.37 mil). UGPCB uses 1 OZ copper on both outer layers (designated 1/1 OZ), ensuring equal current-carrying capacity and conductivity on both sides.

6.3 Surface Finish — Lead-Free HASL

Lead-Free HASL involves immersing the PCB in molten lead-free solder (typically Sn-Cu, Sn-Cu-Ni, or Sn-Ag-Cu alloys), then using high-pressure hot air knives to level and remove excess solder. This produces a uniform, solderable protective coating on the copper surfaces. The process complies with IPC-6012F requirements and RoHS environmental directives.

6.4 Solder Mask and Legend

• Green Solder Mask — Covers all circuit areas except pads, providing insulation, oxidation protection, and short-circuit prevention.

• White Silkscreen Legend — Identifies component reference designators, polarity markers, board part numbers, and revision levels to facilitate assembly and debugging.

VII. Product Performance

7.1 Electrical Performance

7.2 Mechanical Performance

7.3 Reliability

Per IPC-6012F Class 2 requirements, the product must pass the following reliability verifications:

• Thermal Stress Test (288°C, 10 seconds, no delamination or blistering)

• Plated Through-Hole Copper Adhesion Test (minimum average hole-wall copper thickness ≥ 20 μm)

• Solderability Test

• Electrical Continuity and Insulation Resistance Test

VIII. Product Structure

UGPCB’s double-sided through-hole PCB features a symmetrical 2-layer construction. From top to bottom:

1. Top Legend Layer (White Silkscreen)

2. Top Solder Mask Layer (Green Ink)

3. Top Copper Foil Layer (1 OZ, 35 μm)

4. FR-4 Insulating Substrate (1.0 mm thickness)

5. Bottom Copper Foil Layer (1 OZ, 35 μm)

6. Bottom Solder Mask Layer (Green Ink)

7. Bottom Legend Layer (White Silkscreen)

8. Plated Through-Holes (PTH) — Span the full board thickness with copper-plated hole walls enabling interlayer interconnection

IX. Product Features

1. High Routing Density — Double-sided routing delivers 60%–80% higher density than single-sided boards, supporting more complex circuit designs.

2. Highly Reliable Through-Hole Interconnection — Plated through-hole (PTH) technology ensures long-term electrical reliability between layers, with hole-wall copper thickness meeting IPC-6012F Class 2 requirements (≥ 20 μm average).

3. Excellent Flame Retardancy — FR-4 substrate meets UL 94 V-0 flammability rating, ensuring safety under abnormal operating conditions.

4. Lead-Free and Environmentally Friendly — Lead-free HASL surface finish complies with RoHS environmental directives.

5. Fine-Pitch Circuit Capability — Minimum line width of 0.32 mm and minimum spacing of 0.37 mm accommodate medium- to high-density circuit designs.

6. Superior Dimensional Stability — FR-4’s low water absorption (≤ 0.10%) ensures minimal dimensional change in humid environments, preserving assembly accuracy.

7. Mature Manufacturing Process — With 1.0 mm board thickness and 0.236 mm minimum hole diameter, the aspect ratio of only 4.24:1 enables mature processes, high yields, and short lead times.

X. Manufacturing Process Flow

UGPCB’s standard double-sided through-hole PCB manufacturing process:

1. Incoming Material Inspection → Verify FR-4 copper-clad laminate thickness, copper foil quality, and visual defects.

2. Cutting → Cut large-format copper-clad laminate to working panel size (86.9 × 73.58 mm).

3. Drilling → Use high-precision CNC drilling machines to drill all through-holes per the Gerber drill file (minimum diameter 0.236 mm).

4. Plated Through-Hole (PTH) → Deposit a thin copper seed layer on hole walls via electroless copper deposition.

5. Panel Plating → Electrolytically plate copper to build up hole-wall and surface copper to target thickness (1 OZ).

6. Pattern Transfer → Laminate dry film, expose, and develop to form the circuit pattern resist.

7. Etching → Etch away unprotected copper to form the final circuit pattern.

8. Stripping → Remove the resist dry film from circuit traces.

9. Solder Mask Application → Apply green solder mask ink, expose, and develop to expose pads.

10. Surface Finish → Lead-Free HASL.

11. Legend Printing → Screen-print white silkscreen legend.

12. Routing / V-Cut → CNC routing to final board outline.

13. Electrical Testing → Flying probe or fixture testing to verify open/short integrity.

14. Final Quality Control (FQC) → Visual inspection, dimensional sampling, and packaging for shipment.

XI. Application Scenarios

UGPCB Double-Sided Through-Hole FR-4 PCB Boards, with their balanced performance and mature processes, are widely used in:

11.1 Consumer Electronics

• Power adapters and chargers

• Home appliance control boards

• Smart home devices

11.2 Industrial Controls

• PLC programmable logic controllers

• Industrial power modules

• Instrumentation and meters

11.3 Communication Equipment

• Routers and switches

• Communication modules

• Signal conversion devices

11.4 Automotive Electronics

• On-board chargers

• Body control modules (non-safety-critical)

• Infotainment systems

11.5 Medical Devices

• Patient monitor auxiliary boards

• Portable medical equipment (Class 2 applicable)

XII. Product Advantages and Selection Guide

12.1 Why Choose UGPCB Double-Sided Through-Hole PCBs?

• IPC-Compliant Process Control — From material selection to finished goods, full compliance with IPC-6012F, IPC-4101, and other international standards.

• High-Precision Manufacturing — Minimum hole diameter of 0.236 mm and minimum line width of 0.32 mm meet medium- to high-density design requirements.

• Environmental Compliance — Lead-free HASL surface finish complies with RoHS 2.0 directives.

• Proven Reliability — FR-4 substrate has been market-validated for decades with consistent performance.

• Fast Delivery — Standard specifications are stocked with ample raw materials, ensuring reliable lead times.

12.2 Selection Reference

UGPCB Double-Sided Through-Hole PCBs are the ideal choice when your project meets these criteria:

• Moderate circuit complexity that 2 layers can accommodate

• Operating frequency below 1 GHz (FR-4 performs excellently in this range)

• Long-term operating environment not exceeding 120°C

• Cost-sensitive applications demanding high value

XIII. Request a Quote

UGPCB is committed to delivering high-quality PCB manufacturing and turnkey PCBA services to customers worldwide. Whether you need standard-specification double-sided through-hole PCBs or custom requirements (special board thickness, copper weight, surface finish, impedance control, etc.), UGPCB’s expert team provides full support from engineering design to volume production.

Get a Quote Today:

• Submit Gerber files + specifications — receive a quote within 24 hours

• Support from prototype to high-volume production

• Free Design for Manufacturing (DFM) review

Contact UGPCB:
📧 Sales Inquiries: [sales@ugpcb.com]
🌐 Website: [www.ugpcb.com]

XIV. Data Source Declaration

The standards and data cited in this document are sourced from the following authoritative organizations:

1. IPC (Association Connecting Electronics Industries): IPC-6012F Qualification and Performance Specification for Rigid Printed Boards (September 2023); IPC-4101 Specification for Base Materials for Rigid and Multilayer Printed Boards; IPC-2221 Generic Standard on Printed Board Design; IPC-7351 Generic Requirements for Surface Mount Design and Land Pattern Standard

2. UL (Underwriters Laboratories): UL 94 Standard for Tests for Flammability of Plastic Materials for Parts in Devices and Appliances

3. NEMA (National Electrical Manufacturers Association): FR-4 material grade definition

4. Industry Standard Technical Data: FR-4 dielectric constant, dissipation factor, and other material property parameters