Views: 0 Author: Site Editor Publish Time: 2026-07-20 Origin: Site
LDI, the full name of Laser Direct Imaging, is a digital maskless lithography technology that has completely replaced traditional film exposure processes in high-end printed circuit board manufacturing, covering rigid PCB, flexible FPC, HDI boards and IC packaging carrier boards. The traditional PCB exposure process relies on physical photomask films; circuit patterns are transferred to the photoresist coated on substrates through film light shielding. This process inevitably brings multiple defects such as film thermal expansion and contraction deviation, surface dust pollution, film scratches and high film production costs.
Different from the traditional process, LDI directly imports digital circuit files including Gerber and ODB++ into the equipment control system, converts graphic data into controllable laser light signals, and accurately projects tiny laser spots onto the photoresist layer of the board to complete selective exposure without any intermediate mask film. This digital manufacturing method greatly optimizes production flexibility, processing precision and product yield, and has become the standard production configuration for mid-to-high-end circuit factories worldwide.
LDl is a printed board patterning process that uses a laser to directly transfer digital circuit images onto a photoresist-coated substrate using a laser, eliminating the need for phototools. It represents an advanced stage in the evolution of circuit board photolithography, offering higher accuracy and flexibility.
Photoresist is selectively exposed to the laser beam in increments across the substrate in a rastering manner. The image formed can be comparedto the image on a CRT screen, formed from several lines across the screen.
Similar to photolithography, LDl requires a photoresist, although the resist is specially created for laser printing, as the resist is fast-acting compared to conventional photoresist. The resist comes in dry film and liquid options, with the resist application methods being identical to those used in photolithography.
What are the steps involved in the LDl process?
The LDl follows a sequence of surface preparation, resist coating, digital exposure, and etching. Each step ensures precise pattern transfer and minimal variation, which is critical for high-density circuit designs.
Here's the procedure:
1. Scrubbing: This includes removing any oxide layers on the core surface using anti-oxidant baths and mechanical scrubbing with abrasive pads.
Sometimes Isopropyl alcohol is used to remove any organic residues and oil on the core surface.
2. Lamination photoresist: The board panel is coated with a layer of photosensitive material.
3. Loading CAM files: CAM files are then loaded into the laser.
4. Laser printing: The circuit pattern is printed onto the board by the CNC laser.
Etching: Areas of photoresist material that weren't exposed to the laser beam are etched away using acid, leaving behind the desired circuit paths/traces.
6. Photoresist strip: Removal of the photosensitive material
7. Drying: Drying the core/CCL after removal of photo material
No physical film needed: Cut film production, storage and replacement costs, eliminate dimensional deviation caused by film thermal expansion & contraction.
Ultra-high precision: Minimum achievable line width/spacing down to 6–20μm, overlay alignment accuracy up to ±0.5μm, perfectly matching HDI, high-density flexible circuit and chip packaging substrates.
Flexible rapid switching: Modify production patterns by updating digital files only, ideal for small-batch, multi-variety orders.
Higher production yield: Avoid scratches, dust and registration errors brought by film contact exposure.
2. Which Lasers Are Used for LDI Machines?
The core light source of all industrial LDI production equipment is ultraviolet and violet semiconductor laser, whose photon energy can effectively activate the chemical cross-linking reaction of PCB special photoresist. Lasers of different wavelengths are applied to differentiated production scenarios according to precision demand, cost budget and photoresist type:
355nm solid-state ultraviolet laser
It belongs to short-wavelength high-precision light source, with ultra-small focusing spot and ultra-high monochromaticity. The imaging resolution can reach below 5μm line width, which is specially matched with ultra-fine line IC carrier boards and top-grade HDI products that pursue extreme precision. However, the overall equipment cost and later maintenance cost are relatively high, mainly used in advanced packaging circuit production lines with high added value.
375nm fiber-coupled violet laser module
It strikes a perfect balance between exposure precision, service life and overall equipment cost. The wavelength absorption curve fits most liquid photoresist and thin dry film materials of FPC flexible circuits, and the beam uniformity is excellent, which can ensure consistent line edge roughness during mass flexible board production. It is widely selected by medium and high-end soft board manufacturers.
405nm fiber-coupled violet laser module
This is the most mainstream light source for large-volume LDI mass production equipment at present, also the core laser product our company customized for LDI industry clients. Compared with 355nm solid laser, 405nm diode laser has lower power consumption, lower heat generation, longer continuous working life and lower procurement cost. It is compatible with all mainstream PCB exposure materials, including inner layer dry film, outer layer liquid photoresist and solder mask ink. Customized power from 300mW to 12W is available, with stable power fluctuation within ±2%, supporting 24-hour uninterrupted industrial operation.
Special alternative: 1064nm infrared laser
Its photon energy cannot activate conventional UV-sensitive photoresist, so it only matches customized infrared special photoresist for individual thick copper PCB processing scenes. Due to limited imaging precision and narrow material compatibility, it is rarely adopted in mainstream LDI production lines.
Our company provides customized fiber-coupled 375nm & 405nm violet laser modules exclusively for LDI equipment. Each laser module is equipped with built-in constant temperature driving and power closed-loop control system, which effectively suppresses power drift and light decay during long-term scanning exposure, providing stable and consistent exposure energy guarantee for circuit board digital imaging.
BU-LASER is the original manufacturer of laser diode module from 375nm to 980nm, providing you with high-quality OEM & ODM services with over 16 years of mature experience!
