Process And Material Selection, Advantages, And Application Areas of Double-sided Circuit Boards

1、 Core process technology

1. Standard process (through-hole metallization process)

Key technical points of the process, precision requirements

Preparation of FR-4/CEM-3/Aluminum Substrate Cutting → Copper Foil Thickness 1-2oz (35-70 μ m) Size Tolerance ± 0.15mm

Drilling CNC mechanical drilling (aperture ≥ 0.3mm) → plasma debonding slag hole position accuracy ± 0.05mm

Hole metallization PTH (chemical copper deposition):

• Palladium activation → Chemical copper plating (0.5 μ m) → Full plate electroplating (pore copper ≥ 20 μ m) with a depth to diameter ratio of ≤ 8:1

Double sided LDI exposure for graphic transfer → graphic electroplating (copper+tin protection) → alkaline etching to remove film with a line width tolerance of ± 0.07mm

Solder mask and surface treatment spray solder mask ink (green oil) → character printing → HASL/ENIG/OSP three choice solder mask bridge width ≥ 0.1mm

2. Advanced technology (high reliability requirement)

Resin plug hole: Fill the through-hole with epoxy resin to prevent welding short circuit (mandatory requirement for automotive electronics)

Selective gold plating: ENIG immersion in contact area (corrosion-resistant), OSP treatment in welding area (cost reduction of 30%)

2oz thick copper design: outer etched thick copper foil, supports 10A high current power module

2、 Material Selection Guide

Comparison of substrate performance

Material type Dielectric constant (Dk) Thermal conductivity (W/mK) Cost (yuan/㎡) Applicable scenarios

FR-4 epoxy board 4.3-4.7 0.3 50-80 consumer electronics/industrial control motherboard

CEM-3 composite board 4.5-5.0 0.25 30-50 LED lighting/low-cost home appliances

Aluminum substrate -1.5-4.0 100-150 high-power LED/automotive power module

PTFE high-frequency board 2.0-2.2 0.25 200-300 RF module (≤ 6GHz)

The golden rule for selecting materials:

Cost effective first choice: FR-4 (with the best comprehensive performance)

Heat dissipation requirement: Aluminum substrate (reducing thermal resistance by 60%)

High frequency application: PTFE (insertion loss< 0.02dB@5GHz ）

3、 Core Advantage Analysis

1. Electrical and structural performance

Advantages of double-sided panel compared to single panel for improving indicators

The density of double-sided wiring and through-hole jumper components has been increased by 50% in terms of wiring density

Signal integrity via impedance controllable (± 8%), suitable for reducing crosstalk by 20% in circuits below 500MHz

Heat dissipation capability: double-sided copper plating+thermal conductive via, thermal resistance reduced by 30%, equivalent power consumption and temperature drop of 12 ℃

Reliability meets IPC-6012 CLASS 2 standard (industrial grade) with a lifespan of over 10 years (industrial environment)

2. Economic advantages

Cost efficiency ratio: 40-60% lower in cost than 4-layer boards, supporting medium complexity circuits (such as STM32 main control systems)

Production cycle: Batch delivery takes 3-4 days (30% faster than multi-layer boards)

Convenience of maintenance: Through hole light transmission detection failure, repair success rate>90%

4、 Application Fields and Typical Cases

1. Consumer electronics (accounting for 50%)

Smart home: WiFi module (ESP8266 double-sided board), Bluetooth speaker motherboard

Portable devices: power bank control board (2oz thick copper), e-book reader

2. Industrial control (accounting for 30%)

Performance requirements for application scenario technical solutions

PLC I/O module FR-4 double-sided+OSP treatment, moisture and heat resistance (85 ℃/85% RH)

Motor driver aluminum substrate+through-hole heat dissipation design, continuous current 10A, temperature rise ＜ 40 ℃

Industrial sensor CEM-3 substrate+selective gold cost<$2/piece

3. Automotive electronics (accounting for 15%)

Low voltage system: window controller, headlight drive board (FR-4 Tg150 ℃ version)

Sensor: Tire Pressure Monitoring (TPMS) circuit, resistant to -40 ℃ low temperature impact

4. Emerging fields

IoT terminal: LoRa communication module (double-sided hybrid PTFE+FR-4)

Unmanned aerial vehicle tuning: 2oz copper foil+resin plug hole, anti vibration 20G

5、 Process limitations and coping strategies

Effect of defect solution

High frequency loss>1GHz circuit switching to high-frequency substrate (RO4350B mixed voltage) reduces insertion loss from>2dB to< 0.5dB@1GHz

Inter layer interference increases, grounding via (spacing λ/10) reduces EMI by 15dB μ V

Welding virtual soldering step reflow soldering curve+nitrogen protection virtual soldering rate reduced from 3% to 0.5%