Surface Screen Printing is a process of printing patterns, text, logos, or functional coatings on the surface of a product (such as metal, plastic, glass, ceramic, etc.) through screen printing technology. The principle is to use the hollow area of the screen plate to squeeze the ink or paint onto the surface of the substrate to form the desired graphic or text. The process is widely used in electronics, home appliances, automobiles, daily necessities, packaging and other fields, and has both decorative and functional properties.

Core process principles and processes
1. Principle
By using the screen (stencil) as a template, the non-printing area on the screen is blocked with photosensitive adhesive, and the printed area is a hollowed-out dot or pattern.

The squeegee (squeegee) pushes the ink through the screen hollow area at a certain pressure and angle to the surface of the substrate to form a clear pattern.

2. Key processes
Stencil production:

Design Draft: → Film (negative) → Stencil (nylon or stainless steel mesh) Coated with photosensitive adhesive → Exposure (film laminated stencil, UV cured) → Development (uncured photosensitive adhesive is rinsed to form a hollow pattern).

Pre-treatment:

Clean the surface of the substrate (degreasing, dusting, sandblasting, etc.) to ensure ink adhesion (e.g., metal parts need to be phosphated, plastic parts may need flame treatment or primer).

Printing:

The substrate is fixed on the workbench, the screen plate and the surface are kept at a certain distance (off-screen distance), and the squeegee squeezes the ink through the screen to complete single or multiple color printing.

Drying and curing:

Natural drying, hot air drying (80~150°C) or UV curing (fast curing by ultraviolet irradiation, suitable for photosensitive inks).

Post-processing:

Inspection, revision (e.g. defect reprinting), surface protection (e.g. varnish, plating).

Main process characteristics and advantages
Features Description:
Wide range of application It can be used for flat, curved surface (curved screen printing machine is required), concave and convex surface substrates, and has strong material compatibility (metal, plastic, glass, etc.).
Low cost The cost of screen production is low, suitable for small batch customization or mass production, without complex equipment.
High degree of pattern freedom Support fine lines (minimum line width 0.1mm), gradient color, multi-color overprint, can achieve matte, fluorescent, luminous and other special effects.
Functional expansion It can print functional materials such as conductive inks (used in flexible circuits), thermally conductive coatings, insulating layers, and anti-skid lines.
Eco-friendly Eco-friendly materials such as water-based inks and UV inks can be selected to reduce VOC emissions.
Common application scenarios
1. Consumer electronics
Mobile phones / laptops: logos, key characters, decorative textures (e.g. CD pattern of metal case, etched effect).

Appliance panel: operation button logo, brand LOGO (such as refrigerator, washing machine surface silk screen).

Electronic components: resistor/capacitance parameter identification, character layer of the PCB board.

2. Automotive industry
Instrument panel identification: scales, pointers, warning symbols (high and low temperature resistant inks).

Interior parts: steering wheel logo, center console text (scratch-resistant coating).

Exterior trim: Wheel branding, window trim pattern.

3. Daily necessities and packaging
Cosmetic containers: brand pattern on the glass bottle, color printing on the surface of the hose.

Toys / Stationery: Patterns of plastic toys, cartoon prints on the surface of water cups.

Packaging and printing: text and patterns of cartons and plastic boxes (combined with pad printing process for irregular surfaces).

4. Functional applications
Conductive ink printing: the circuit circuits of flexible electronic devices (e.g., e-skins, wearable devices).

Sensor coatings: Sensitive material layers for printed pressure sensors and temperature sensors.

Optics: Shade ink for LCD panel (BM black matrix), camera filter identification.

Key technical difficulties and solutions
1. Insufficient adhesion
Causes: Incomplete surface cleaning, poor ink and material compatibility.

Solution:

Pre-treatment (e.g. plasma cleaning, flame treatment) to enhance surface energy;

Choose a special ink (e.g. ABS for plastics, metal paint).

2. Chromatic deviation (multi-color printing)
Reason: insufficient positioning accuracy of the screen and deformation of the substrate.

Solution:

Use of high-precision stencil positioning systems (e.g. pin positioning);

Control the ambient temperature and humidity during color separation printing to reduce the impact of thermal expansion and contraction of materials.

3. Lack of fineness (e.g. small print, thin lines)
Reason: low mesh number of stencils, inappropriate ink viscosity.

Solution:

Increase the number of screen mesh (e.g. 200~300 mesh for fine patterns);

Adjust the ink viscosity (low viscosity inks for fine lines, high viscosity for thick films).

4. It is difficult to print curved surfaces
Cause: The curvature of the surface leads to uneven ink distribution.

Solution:

Using a curved screen printer (e.g. cylinder printing) to achieve uniform pressure application by rotating the substrate;

Use an elastic scraper or a soft scraper to adapt to the contours of the surface.

Process innovation and development trends
Digitalization and intelligence

The introduction of digital screen production technology (such as laser direct plate making, LDS) eliminates the need for film films, and improves the accuracy and efficiency of screen production.

The intelligent screen printer integrates a visual inspection system (e.g., AI automatically identifies and adjusts the color register).

Functional material expansion

Nano ink: conductive silver paste, thermally conductive ceramic ink is used in microelectronic devices.

Light-curing materials: UV inks achieve instantaneous curing, which is suitable for high-speed production on assembly lines.

Biodegradable inks: used for environmentally friendly packaging and disposables.

Special surface printing

3D surface printing: Combined with thermal transfer or pad printing process, it can achieve full coverage printing of complex surface (such as car lamp covers, helmets).

Micro/nano structure printing: Nano-scale optical textures (e.g., anti-glare coatings, anti-reflection coatings) are produced through high-precision stencils.

Green process upgrading

Promote water-based inks and solvent-free inks to reduce environmental pollution.

Transition from stencil materials to recyclable polymers such as PET mesh.

Comparison with other surface treatment processes
Process Advantages Limitations Typical Applications
Silk screen printing low cost, flexible pattern, strong functionality Limited surface accuracy, film thickness uniformity General identification, multi-color pattern, conductive circuit
Pad printing Suitable for irregular surfaces Limited in size and less efficient Toys, cutlery patterns
Thermal transfer printing Bright color, high adhesion Need special transfer film, high cost Sports equipment, furniture wood grain
Laser marking, permanent marking, high precision, single color, surface micro-damage, electronic component number, medical device identification
Spraying Large-area coloring, high efficiency, low degree of pattern freedom, automobile body, home appliance shell coating
summary
With its flexibility, low cost and versatility, the surface screen printing process has become one of the core technologies in industrial design to achieve product personalization, branding and functionalization. With the development of material science and intelligent manufacturing, the screen printing process is evolving in the direction of high precision, intelligence and green, and will play a more important role in flexible electronics, new energy, biomedical and other fields in the future. Designers need to be familiar with the characteristics of the process, combine materials and design goals, and fully release the innovation potential of the screen printing process.