New UV laser processing technology for PCB boards and substrates
Since the ablation limit of epoxy is lower than that of copper (yellow), the cleaning step (green) cannot penetrate into the underlying copper. The beam is softly illuminated, balancing material thickness and uniform tolerances.
Develop HDIs via UV laser processing:
Process A: 4-step process with mixed wetting and laser processes; mask tolerances range between 50 and 70μm, with typical hole sizes of 100 to 125μm.
Process B: 2-step laser process and 1-step wetting process; due to the diffraction of CO2 on the mask, the diameter of small holes is about 60μm. The limit of copper opening thickness that can be provided for the specially treated copper material by CO2 is 7μm. This process still requires smudge removal.
Process C: 1-step laser process; UV laser has no restrictions on drilling inner and outer copper, and it includes an additional cleaning process that reduces drilling contamination to a minimum, potentially replacing the need for a separate drilling contamination process.
UV lasers have the ability to condense an entire hole process into a single laser step, eliminating the need for de-drilling and improving pulse pattern plating. Unlike CO2 lasers, aggressive besmearing procedures are not necessary with UV lasers, resulting in enhanced hole shape precision, reduced wicking, and minimized barrel distortion.
Other applications and quality outcomes of UV lasers include blind holes, double layer vias, and through holes.
In terms of flexibility, the new laser system is capable of performing intricate drawing operations in addition to focused irradiation in the hole. This enables the cutting of thin line patterns and the removal of solder mask post-buried mask. Nearly any shape within the machining area can be processed. While laser ablation of the solder mask has traditionally been used to rectify minor faults and damaged pads, HDI technology demands larger openings and precise positioning. Speeds of up to 100+ pads per second can be achieved for BGA and FC, with a cost of approximately 0.5 cents per IC for 128 pads. When drawing thin lines, the laser track engraves the graphics at speeds reaching 1000mm/s. The resulting tin patterns are etched to maintain track width spacing and minimize side effects. With a copper thickness of 12im, patterns of less than 2mil/2mil can be achieved, including 2mil/2mil fan-out for IC and MCM patterns. Direct drawing of thin line graphics is restricted by drawing speed, with fan-out taking less than 1 second and complete graphics in a 40×40mm area requiring 10 to 15 seconds.
In conclusion, UV laser systems offer a complementary solution to CO2 drilling tools, providing greater flexibility and complexity for drilling due to their short wavelengths and small spots. While there may still be a performance gap compared to CO2 lasers, particularly in macropores, advancements in high-power and high-frequency UV lasers are narrowing this difference. The number of processing steps required for UV laser vias is decreasing, with besmearing steps minimized. Beyond drilling, UV systems can be utilized for direct drawing and precision solder mask ablation, adding further value. There is ample room for improvement in UV laser systems throughput through smaller pulse widths, higher frequencies, increased power, and high-speed servo operation. The market is progressively embracing UV laser systems as integral tools for PCB board production.
Since the ablation limit of epoxy is lower than that of copper (yellow), the cleaning step (green) cannot penetrate into the underlying copper. The beam is softly illuminated, balancing material thickness and uniform tolerances.
Develop HDIs via UV laser processing:
Process A: 4-step process with mixed wetting and laser processes; mask tolerances range between 50 and 70μm, with typical hole sizes of 100 to 125μm.
Process B: 2-step laser process and 1-step wetting process; due to the diffraction of CO2 on the mask, the diameter of small holes is about 60μm. The limit of copper opening thickness that can be provided for the specially treated copper material by CO2 is 7μm. This process still requires smudge removal.
Process C: 1-step laser process; UV laser has no restrictions on drilling inner and outer copper, and it includes an additional cleaning process that reduces drilling contamination to a minimum, potentially replacing the need for a separate drilling contamination process.
UV lasers have the ability to condense an entire hole process into a single laser step, eliminating the need for de-drilling and improving pulse pattern plating. Unlike CO2 lasers, aggressive besmearing procedures are not necessary with UV lasers, resulting in enhanced hole shape precision, reduced wicking, and minimized barrel distortion.
Other applications and quality outcomes of UV lasers include blind holes, double layer vias, and through holes.
In terms of flexibility, the new laser system is capable of performing intricate drawing operations in addition to focused irradiation in the hole. This enables the cutting of thin line patterns and the removal of solder mask post-buried mask. Nearly any shape within the machining area can be processed. While laser ablation of the solder mask has traditionally been used to rectify minor faults and damaged pads, HDI technology demands larger openings and precise positioning. Speeds of up to 100+ pads per second can be achieved for BGA and FC, with a cost of approximately 0.5 cents per IC for 128 pads. When drawing thin lines, the laser track engraves the graphics at speeds reaching 1000mm/s. The resulting tin patterns are etched to maintain track width spacing and minimize side effects. With a copper thickness of 12im, patterns of less than 2mil/2mil can be achieved, including 2mil/2mil fan-out for IC and MCM patterns. Direct drawing of thin line graphics is restricted by drawing speed, with fan-out taking less than 1 second and complete graphics in a 40×40mm area requiring 10 to 15 seconds.
In conclusion, UV laser systems offer a complementary solution to CO2 drilling tools, providing greater flexibility and complexity for drilling due to their short wavelengths and small spots. While there may still be a performance gap compared to CO2 lasers, particularly in macropores, advancements in high-power and high-frequency UV lasers are narrowing this difference. The number of processing steps required for UV laser vias is decreasing, with besmearing steps minimized. Beyond drilling, UV systems can be utilized for direct drawing and precision solder mask ablation, adding further value. There is ample room for improvement in UV laser systems throughput through smaller pulse widths, higher frequencies, increased power, and high-speed servo operation. The market is progressively embracing UV laser systems as integral tools for PCB board production.
