Something You Ought to Know About PCB Silkscreen Printing
6 min
- Benefits of PCB Silkscreen
- Silkscreen Techniques in PCB Manufacturing
- Conclusion
- Frequently Asked Questions (FAQ)
PCB silkscreen (also called legend or nomenclature) is the layer of printed text, symbols, marks, and images on a PCB surface. It is applied on top of the solder mask layer using special epoxy ink, providing critical information for component placement, assembly instructions, testing, and identification.
JLCPCB applies silkscreen on the top and/or bottom side (component side) after the solder mask and copper layers are completed. Common ink colors are white (default) or black for optimal contrast against the solder mask background.
Benefits of PCB Silkscreen
There are several key advantages to adding silkscreen:
1. Component Identification
2. Assembly Guidance
3. Circuit Understanding
4. Branding and Logo Placement
5. Aesthetics
6. Compliance and Certification
7. Documentation and Reference
For example, clear component labels (e.g., "R1", "C1") speed up assembly and troubleshooting. On JLCPCB, silkscreen can also include version numbers, dates, or logos. Note: JLCPCB automatically removes silkscreen over pads, vias, or traces to avoid assembly issues.
Silkscreen Techniques in PCB Manufacturing
JLCPCB primarily uses Liquid Photo Imaging (LPI) for its balance of precision, resolution, and cost-effectiveness in volume production. Below are the three common methods, with their processes and key advantages/disadvantages.
Manual screen printing
This traditional method applies epoxy ink through a nylon mesh stencil by hand. It is suitable when line widths exceed 7 mil (0.178 mm) and registration tolerance is ±5 mil. After printing, the board is cured in an oven.
Pros: Extremely low setup cost for very small runs or prototypes—no photomask or digital files needed; highly flexible for last-minute design changes (just modify the stencil); works well on uneven or curved surfaces (though rare for PCBs); ink thickness can be controlled manually for bolder legends. Ideal for hobbyists or low-volume custom boards.
Cons: Highly labor-intensive and operator-dependent—variations in squeegee pressure or angle can cause uneven ink distribution, smudging, or incomplete coverage; poor repeatability across batches; limited resolution (struggles with fine text <1 mm or thin lines); risk of misalignment between top/bottom sides; not scalable for medium/high volume due to time per board.
Liquid photo imaging (LPI)
LPI is the industry-standard method for modern mass production, including JLCPCB's primary choice. The detailed process:
1. The completed PCB (copper + solder mask) is cleaned and coated with liquid photo-sensitive epoxy ink (usually via curtain coating or spray for uniform thickness ~20–30 μm).
2. The ink is pre-baked to remove solvents.
3. A photographic film (photomask) with the legend artwork is aligned and placed in contact with the board.
4. UV light exposes the ink through the photomask—exposed areas polymerize/harden.
5. Unexposed ink is washed away in a developer solution (alkaline or solvent-based).
6. Final high-temperature curing ensures durability.
Double-sided boards require separate processing for each side with precise alignment pins.
Pros: Excellent resolution and registration accuracy (±0.05 mm typical); supports very fine features (down to 0.15 mm lines/0.8 mm text); highly consistent and automated once photomask is created; thick, durable ink layer resistant to chemicals and reflow soldering; perfect for complex, dense legends with logos, barcodes, or small text; scalable for high-volume production with minimal per-board variation.
Cons: Requires expensive photomask fabrication for each design revision; multi-step process (coating → pre-bake → exposure → develop → cure) increases setup time and facility requirements (cleanroom, UV exposure units, chemical handling); higher waste from developer chemicals; not ideal for ultra-small runs due to photomask cost.
Direct legend printing (DLP)
This fully digital, non-contact method uses specialized inkjet printers adapted for PCBs. The process:
1. The PCB is loaded into the printer after solder mask curing.
2. Piezoelectric or thermal inkjet heads deposit tiny droplets of UV-curable epoxy ink directly onto the surface, following digital Gerber/artwork files.
3. Each printed line/pass is immediately UV-cured for instant hardening.
4. Multiple passes build desired ink thickness; no physical contact with the board.
5. Final inspection and optional additional cure.
No photomask or stencil required—purely digital workflow.
Pros: Highest flexibility—design changes are instant (just update the file); fastest turnaround for prototypes and small-to-medium batches; excellent precision for intricate patterns, gradients, or multi-color legends (if equipment supports); minimal waste (ink only where needed); easy double-sided printing with automated flipping; supports variable data (e.g., serial numbers per board).
Cons: Equipment is very expensive (industrial inkjet systems cost significantly more than LPI setups); ink formulation is specialized and costly; potential issues with ink adhesion on certain solder mask types; slightly thinner ink layer compared to LPI (may affect long-term durability); throughput slower than LPI for very high volumes; limited availability at many fabs (JLCPCB offers on request but not standard).
Comparison Table (JLCPCB Specifications)
| Method | Description | Min Line Width/Text Height | Pros | Cons | JLCPCB Usage |
| Manual Screen Printing | Ink applied through stencil by hand | ~0.178 mm / 1 mm | Low cost for prototypes | Labor-intensive, lower resolution | Rarely used |
| Liquid Photo Imaging (LPI) | Photo-sensitive epoxy ink, UV exposed | 0.15 mm / 0.8 mm | High resolution, precise, automated | More setup time | Primary method |
| Direct Legend Printing (Inkjet) | Digital inkjet directly onto board | 0.15 mm / 0.8 mm | Fast for small batches, flexible | Higher equipment cost | Available on request |
Note: JLCPCB default silkscreen color is white (black optional). Silkscreen is automatically clipped from pads and vias.
Conclusion
PCB silkscreen is essential for usability, assembly, and branding. When designing for JLCPCB, use clear fonts, avoid placing silkscreen over pads/vias, and adhere to minimum size rules (0.15 mm line, 0.8 mm text) for best results. This ensures high-quality production and easy assembly.
Frequently Asked Questions (FAQ)
1. What is PCB silkscreen?
Silkscreen (legend) is the printed layer of text, symbols, and marks on the PCB surface, applied over the solder mask using epoxy ink for component identification, assembly guidance, and branding.
2. What are the key benefits of adding silkscreen?
Improves component identification, assembly/troubleshooting speed, circuit understanding, branding, aesthetics, compliance markings, and long-term documentation.
3. What silkscreen specifications does JLCPCB support?
Default white ink (black optional); min line width 0.15 mm (6 mil); min text height 0.8 mm (31 mil). Silkscreen is automatically clipped from pads and vias.
4. Which silkscreen method does JLCPCB primarily use?
Liquid Photo Imaging (LPI) for high resolution and reliability in production; manual rarely used; direct inkjet available on request.
Popular Articles
• PCB Silkscreen: All You Need to Know
• The Comprehensive Guide to Circuit Symbols: Key to Understanding Electrical and Electronic Diagrams
• Design Guidelines for PCB Using FR4 Substrates
• Choosing the Best PCB Color-Enhancing Aesthetics and Functionality
• PCB Board Design: A Step-by-Step Guide for Beginners
Keep Learning
ESP32 Power Consumption Explained: Current Draw, Sleep Modes, and Battery Life
Key Takeaways Power consumption by mode: The ESP32 draws around 240 mA during Wi-Fi transmission, 0.8 mA in light sleep, and just 10 µA in deep sleep, based on Espressif's typical datasheet figures. Deep sleep current: The ESP32 can draw 10 µA in deep sleep, with only the RTC timer and memory remaining powered. Keeping the ULP coprocessor running increases current consumption to around 100–150 µA. Development board power consumption: A typical ESP32 development board can draw around 6.5 mA even in dee......
ESP32 Pinout Reference: Which GPIO Pins Are Safe to Use and Avoid?
Key Takeaways GPIO count: The ESP32 chip has 34 GPIOs, and the ESP32-WROOM-32E module exposes 26 of them. General-purpose pins: Fifteen module GPIOs carry no boot, flash, or input-only restrictions: GPIO4, GPIO13, GPIO14, GPIO16 to GPIO19, GPIO21 to GPIO23, GPIO25 to GPIO27, GPIO32, and GPIO33. Strapping pins: GPIO0, GPIO2, GPIO5, GPIO12, and GPIO15 are sampled at reset, so any circuit connected to them must maintain the level required by the boot mode. Input-only pins: GPIO34, GPIO35, GPIO36, and GPI......
PCB Silkscreen: All You Need to Know
Key Takeaways The PCB Silkscreen Guide demonstrates that a properly designed legend layer is essential to prevent assembly failures and ensure long-term hardware reliability. By mastering modern manufacturing methodologies like Direct Legend Printing (DLP) and aligning layouts with JLCPCB's strict DFM design rules—including the absolute 0.8 mm character height limit and the automated 0.15 mm silkscreen clipping protocol driven by solder mask precedence—engineers can seamlessly eliminate cold joints an......
A Beginner's Guide to Basic Electronic Components: Functions, Symbols & Uses
Every circuit, from a simple LED flashlight to a microcontroller board, is built from the same handful of common electronic components. This guide breaks down the ten basic electronic components you will encounter most often: What each component does How it works Key specifications Where engineers use it By the end, you will be able to recognize these electronic circuit components on a schematic, a PCB, or a parts bin, and know exactly why each one is there. These electronic components are the buildin......
How to Read and Create PCB Schematics
Key Takeaways Read Schematics: Understand symbols, net labels, and component values. Design in EasyEDA: Place components and create circuit connections. Run Design Checks: Use ERC and DRC to identify potential issues. Verify Components: Check pin assignments and PCB footprints. Prepare for Manufacturing: Validate PCB layouts and manufacturing files. Printed circuit board (PCB) design begins with a clear understanding of how the electronic circuit should function. A schematic diagram represents the cir......
Maximizing Circuit Reliability with PCB Test Points and Smart DFT
Key Takeaways Early Fault Catching: Test points drastically reduce diagnosis time and prevent costly field failures. Standard Pad Sizing: Use 1.0 mm flat copper pads with 2.54 mm spacing for optimal fixture contact. Protect High-Speed Signals: Keep branch traces short to prevent capacitive loading and resonance. Single-Sided Access: Place all test pads on the bottom layer to cut fixture costs. Right Test for Volume: Use flying probe for prototypes and bed-of-nails ICT for mass production. A PCB test p......