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Picosecond vs. Nanosecond Lasers: The Ultimate Guide to FPC and PCB Processing Excellence
In the rapidly evolving world of electronics manufacturing, the demand for smaller, thinner, and more flexible circuits is at an all-time high. Flexible Printed Circuits (FPC) and High-Density Interconnect (HDI) PCBs require surgical precision that traditional mechanical methods can no longer provide.
This brings us to the two heavyweights of industrial laser micro-machining: Nanosecond (ns) and Picosecond (ps) lasers. While both are used for cutting, drilling, and etching, the choice between them can determine your product's reliability and yield.
1. Technical Specifications: How Nanosecond and Picosecond Lasers Compare
Understanding the technical foundations is the first step in choosing the right tool for your production line.
Similarities in Industrial Specs
Despite their differences in speed, they share common industrial DNA:
Wavelength Availability: Both technologies offer standard industrial wavelengths, including 1064 nm (Infrared), 532 nm (Green), and 355 nm (Ultraviolet/UV). UV is particularly popular in PCB processing due to its high absorption rate in polymers and copper.
Integration: Both can be integrated into high-speed galvanometric scanning systems and CNC workstations.
Industrial Reliability: Modern ps and ns lasers are designed for 24/7 high-volume manufacturing environments.
The Critical Differences
Feature | Nanosecond (ns) Laser | Picosecond (ps) Laser |
Pulse Duration | 10^{-9} seconds (e.g., 10 ns – 100 ns) | 10^{-12} seconds (e.g., 1 ps – 20 ps) |
Peak Power | Megawatts (MW) | Gigawatts (GW) |
Ablation Mechanism | Photothermal (Melting/Evaporation) | Photoacoustic (Cold Processing) |
Precision | Standard (Micro-scale) | Ultra-precision (Sub-micro scale) |
2. Why Picosecond Lasers are Superior for "Carbonization" Prevention
In industrial terms, carbonization refers to the charring or burning of the material surrounding the laser cut. This creates a Heat Affected Zone (HAZ), which can lead to circuit failure, poor insulation, or structural weakness in FPCs.
The Science of "Cold Processing"
The primary reason picosecond lasers avoid carbonization is the relationship between pulse duration and Thermal Relaxation Time (TRT).
Nanosecond Lasers (The "Hot" Process): A nanosecond pulse is relatively "slow." It gives enough time for thermal energy to conduct into the surrounding material. This heat causes the material to melt, boil, and eventually char (carbonize) before it is removed.
Picosecond Lasers (The "Cold" Process): A picosecond pulse is so fast that it finishes its interaction with the material before the heat can travel to the neighboring atoms. Instead of melting, the high peak power causes multiphoton absorption, turning the material directly into plasma. This is known as "Cold Processing," resulting in a clean cut with virtually zero carbonization.
3. FPC & PCB Processing: A Deep Dive into Performance
When processing materials like Polyimide (PI) and Copper (Cu), the difference in results is striking.
FPC Polyimide (PI) Cutting & Coverlay Opening
Nanosecond Result: Often shows a "darkened" or "yellowed" edge. The heat can cause the PI to curl or the adhesive layer to bleed, affecting the final assembly.
Picosecond Result: Clean, sharp edges with the material’s original color maintained. There is no residue, which is vital for the adhesion of subsequent layers.
PCB Micro-Via Drilling & Copper Ablation
Nanosecond Result: Drilled holes may have a "conical" shape with slag (re-solidified molten copper) at the entrance. This requires aggressive chemical cleaning before plating.
Picosecond Result: Achieves perfectly cylindrical "straight-walled" holes. The copper is vaporized cleanly, leaving no slag and significantly reducing the need for post-processing.
4. Summary: Choosing the Right Tool for Your Application
Application | Recommended Laser | Primary Reason |
High-End FPC Cutting | Picosecond | Zero carbonization, maintains flexibility. |
HDI PCB Blind Via Drilling | Picosecond | High aspect ratio, no molten residue. |
Rigid PCB Cutting (Thick) | Nanosecond | Cost-effective, higher material removal rate. |
Simple Component Marking | Nanosecond | Efficient and significantly lower investment cost. |
Conclusion: The Future is Ultra-Fast
While nanosecond lasers remain a cost-effective workhorse for many "rougher" industrial tasks, the Picosecond laser is the clear winner for high-precision electronics. By eliminating carbonization and the Heat Affected Zone, ps lasers allow engineers to push the boundaries of FPC and PCB design, ensuring higher yields and superior product reliability.
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What are the precautions for operating a laser marking machine?
1. It is strictly prohibited to start the laser power supply and Q-switching power supply when there is no water or the water circulation is abnormal.
2. The Q power supply is not allowed to operate without load (i.e., the output terminal of the Q power supply should be left floating).
3. In case of any abnormal phenomenon, first turn off the galvanometer switch and the key switch, and then conduct a check.
4. It is not allowed to start other components before the krypton lamp is lit to prevent high voltage from entering and damaging the components.
5. Pay attention to leaving the output terminal (anode) of the laser power supply suspended to prevent sparking and breakdown with other electrical appliances.
6. Keep the internal circulating water clean. Regularly clean the water tank and replace it with clean deionized water or pure water.
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What should we do when laser intensity decreases and the marking is not clear enough?
1. Turn off the machine and check if the laser resonant cavity has changed; Fine-tune the resonant cavity lens. Make the output light spot the best;
2. The acousto-optic crystal is offset or the output energy of the acousto-optic power supply is too low;
Adjust the position of the audio-visual crystal or increase the working current of the audio-visual power supply;
3. The laser entering the galvanometer deviates from the center: Adjust the laser;
4. If the current is adjusted to around 20A but the light sensitivity is still insufficient: the krypton lamp is aging. Replace it with a new one.
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How to maintain a UV laser cutting machine?
1. It is required to carry out regular cleaning every day, remove debris from the countertop, limiters and guide rails, and spray lubricating oil on the guide rails
2. The waste materials in the collection box should be cleared regularly to prevent excessive waste from blocking the exhaust port.
3. Clean the chiller once every 15 days, drain all the internal water, and then fill it with fresh pure water.
4. The reflector and focusing lens should be wiped with a special cleaning solution every 6 to 8 hours.
When wiping, use a cotton swab or cotton swab dipped in the cleaning solution to wipe from the center to the edge of the focusing lens in a counterclockwise direction.
At the same time, be careful not to scratch the lens.
5. The indoor environment can affect the lifespan of the machine, especially in damp and dusty conditions.
A damp environment is prone to causing rust on the reflective lenses and also easily leading to short circuits, discharge and sparking of the velvet laser.
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What accidents might be caused by the laser emission when using a laser cutting machine?
(1) A fire was caused by the laser coming into contact with flammable materials.
Everyone knows that the power of laser generators is very high, especially when it comes to high-power laser cutting machines, the temperature of the emitted laser is extremely high. The possibility of a fire being caused when a laser beam comes into contact with flammable objects is very high.
(2) Harmful gases may be produced when the machine is in operation.
For instance, when cutting with oxygen, it undergoes a chemical reaction with the cutting material, generating unknown chemical substances or fine particles and other impurities. After being absorbed by the human body, it may cause allergic reactions or discomfort in the lungs and other respiratory tracts. Protective measures should be taken when conducting work.
(3) Direct laser exposure to the human body can be harmful.
The damage caused by lasers to the human body mainly includes damage to the eyes and skin. Among the harms caused by lasers, the damage to the eyes is the most severe. Moreover, damage to the eyes is permanent. So when doing homework, you must pay attention to protecting your eyes.
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What is the focused spot diameter of nanosecond, picosecond and femtosecond laser?
Nanosecond: The light spot is 0.5-1mm.
Picosecond: The focused spot is around 0.02mm.
Femtosecond: Under the action of a laser beam with a high repetition rate of 100-200KHz and a very short pulse width of 10ps,
the focused spot diameter is as small as 0.003mm.
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What are the main applications of UV laser cutting machine?
The UV laser cutting machine can be used for cutting and depaneling PCB.
It can precisely cut and shape various types of PCB circuit boards with V-CUT and stamp holes, and open Windows and covers.
It can also be used for separating packaged circuit boards and ordinary smooth boards.
It is suitable for cutting various types of PCB substrates, such as ceramic substrates, rigid-flex boards, FR4, PCBs, FPCs, fingerprint recognition modules, cover films, composite materials, copper substrates, aluminum substrates, etc.
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Precautions for laser cutting machines to process various metal materials?
Copper and brass:
Both materials have high reflectivity and excellent thermal conductivity.
Brass with a thickness of less than 1mm can be processed by nitrogen laser cutting.
Copper with a thickness of less than 2mm can be cut. The gas used for laser cutting processing must be oxygen.
Copper and brass can only be cut when a "reflective absorption" device is installed on the system. Otherwise, reflection will damage the optical components.
Synthetic materials:
Processable synthetic materials include: thermoplastics, thermosetting materials and artificial rubber.
Aluminum:
Despite its high reflectivity and thermal conductivity, aluminum materials with a thickness of less than 6mm can be cut, depending on the type of alloy and the capacity of the laser.
When cutting with oxygen, the cutting surface is rough and hard.
When nitrogen is used, the cutting surface is smooth.
Pure aluminum is extremely difficult to cut due to its high purity.
Only when a "reflection and absorption" device is installed on the fiber laser cutting machine system can aluminum materials be cut.
Otherwise, reflection will damage the optical components
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What should be paid attention to when laser cutting stainless steel?
Laser cutting processing of stainless steel requires the use of oxygen, under the condition that edge oxidation is not a concern.
If nitrogen is used to achieve an edge free of oxidation and burrs, no further processing is required.
Coating an oil film on the surface of the sheet will achieve a better perforation effect without reducing the processing quality.