Direct Laser Printing Benefits Explored
In the world of Printed Circuit Board (PCB) fabrication, a new method known as Laser Direct Imaging (LDI) is making waves. This modern approach, preferred by PCB manufacturers, particularly for High Density Interconnect (HDI) circuit fabrication, offers numerous advantages over traditional methods.
The LDI process begins with the application of a special photoresist, which comes in both dry film and liquid options. This photoresist is then heated to bind it to the core surface, a process known as lamination photoresist. Unlike traditional photolithography, LDI does not employ a phototool, instead using a computer-controlled laser beam to directly define circuit paths onto the board.
In traditional photolithography, a photographic mask called a phototool is created from a drawing and placed on a panel covered by photoresist, which is then exposed to a UV light source to harden or develop. However, this method is affected by various factors such as dirt, fibers, smears, scratches, diffraction of light, temperature and humidity variations, and has greater limitations in substrate alignment.
On the other hand, LDI offers enhanced resolution, precision, and consistent imaging. The process of etching unwanted copper on the board is the same, using solvents like ferric chloride, cupric chloride, ammoniacal etchant, sulphuric and chromic acid, alkaline etchants, and copper ammonia complex ion.
One of the key advantages of LDI is its speed. By eliminating the need for film production steps, LDI speeds up prototyping and shorter runs. However, in high-volume manufacturing, traditional photolithography with steppers can achieve higher throughput.
In terms of precision, LDI offers higher precision and finer pattern definition, suitable for advanced, fine-line PCBs. LDI layer registration results in zero-zero registration and reduced variations compared to photolithography, with only 5-micron variations depending upon the flatness of the board. In contrast, photolithography registration has 15-20-micron variations.
Automatic Optical Inspection (AOI) is a process used to check the existing CCL against circuit patterns that are present in the system. Both LDI and traditional photolithography use this process, with AOI equipment including high-definition cameras and built-in processing software.
In conclusion, while LDI provides greater precision and flexible patterning without physical masks, it can have limitations in high-volume manufacturing throughput compared to stepper-based photolithography tools. However, many modern PCB manufacturers increasingly adopt LDI to leverage its precision and turnaround advantages, while traditional photolithography remains relevant for very high-volume or large-format production where throughput benefits outweigh mask costs.
References: 1. PCBWeb 2. Altium 3. CyberOptics 4. PCB007 Magazine 5. Design News
Data-and-cloud-computing technology can be harnessed to optimize the LDI process in PCB fabrication. For instance, predictive analytics can help in minimizing the variables that affect the lamination photoresist process, ensuring consistent imaging and precision.
Similarly, cloud-based platforms can facilitate seamless collaboration between designers, engineers, and manufacturers, enhancing the efficiency of prototyping and reducing turnaround times in lean manufacturing environments, aligning with the speed advantage offered by LDI.
