Flexible Printed Circuits

Lasers are widely used in the processing of flexible circuit boards for operations such as singulation, or depaneling, coverlay patterning, and drilling holes and vias. But, not all lasers are the same.

The optimal lasers to use for FPC processing are UV, or ultraviolet, wavelength lasers with short pulses and high repetition pulse rates. Shorter laser wavelengths allow smaller beam spot sizes and tighter focusing, which is beneficial for FPC processing in a number of ways:

• Higher precision operations
• Achieve smaller dimensions for even more flexibility and miniaturization
• Less material wasted, allowing more circuits to fit on a panel

Such results are not possible with longer-wavelength lasers, such as CO2 lasers. Only the tighter focus provided by shorter wavelength UV lasers provide beam spot sizes sufficiently small for drilling the required hole dimensions that will enable further miniaturization of FPCs.

Lasers with short pulses and, in combination, higher repetition rates are advantageous because in general, the shorter, or faster, the pulse, the higher the quality of a cut or drill will be. Shorter pulse widths can deliver intense peak powers resulting in:

• Nonlinear absorption at the sample for instantaneous material vaporization
• Very minimal heat transfer into the material
• Much smaller heat-affected zone, or HAZ
• Higher throughput and fewer part failures

While most commercially available pulsed CO2 lasers have pulse widths in the millisecond or microsecond range and repetition rates up to a few hundred kHz, by contrast, Spectra-Physics UV diode-pumped solid state lasers feature pulse widths in the nanosecond range and rep rates up to 500 kHz.

Another feature that can be provided by Spectra-Physics UV diode-pumped solid state lasers is high power. This allows faster operations, such as cutting, which results in higher yields and meeting the throughput requirements for FPC processing. At the same time, it is important to note that the quality of the operation will not be sacrificed for speed due to the benefits provided by the shorter pulse widths and high repetition rates.

UV wavelengths also contribute to efficient processing, as they are well absorbed by a variety of materials in FPCs, including copper and polyimide. Thus, the high beam intensity with smaller beam spot sizes achievable with UV wavelengths that Spectra-Physics lasers offer can efficiently remove copper, while a lower beam intensity with the same type of laser can cut dielectric material without damaging the bottom copper layer.

MKS has many solutions to help meet the current and future flexible printed circuit board manufacturing challenges.

The first challenge that often comes to mind is maximizing throughput and yield. MKS offers UV and green short-pulsed lasers, including high power lasers with pulse control, that can be used for singulation or depaneling, coverlay patterning, and drilling both blind via holes and through-vias. We believe that UV lasers are superior to longer-wavelength CO2 lasers for FPC processing. To ensure that the laser system is performing optimally, MKS offers fast laser measurement and profiling instruments. To manage the high power lasers, MKS also provides high power/high fluence optics for optimal results. And to position components for a process quickly and accurately, MKS can provide high-speed, high-precision motorized positioners.

Another challenge is to improve the quality and reliability of FPCs. Our nanosecond and ultrafast lasers can provide the cleanest cuts and drills with the least amount of thermal and other damage, leading to higher quality and reliability. Additionally, MKS' optical mounts are very robust and stable, so that laser performance will not decline easily over time.

As flexible circuit boards are becoming more and more miniaturized, drilling vias, depaneling and coverlay patterning all become more challenging. The smaller beam spot sizes enabled by the short wavelengths of UV lasers that MKS provides can meet the smaller dimensional requirements presented by miniaturized FPCs.

• 50+ years and thousands of alignment systems for optical applications
• Long-term partner to semiconductor manufacturing companies
• Full range of products: lasers, optics, motion, opto-mechanics, beam analysis
  • Custom capabilities
  • Product availability
• Ability to scale with you
• Global corporation and presence

Lasers	Beam Analysis	Motion Control	Opto-Mechanics
UV and green lasers Nanosecond and ultrafast lasers DPSS Q-switched lasers	High power laser thermal sensors High power beam profilers Laser power/energy meters	Full range of motorized stages Motion controllers Manual Positioners Custom assemblies	High-energy Optics UV, visible and IR optics CO2 lenses Mirror mounts Lens positioners

• Application Requirements
  • Function
  • Type of Material & Thickness
  • Speed
  • Resulting Size of Heat Affected Zone (HAZ)\
• Laser Specifications
  • Wavelength
  • Power
  • Pulse Width & Repetition Rate
  • Stability
• MKS Laser Applications in FPC
  • Hole and via drilling
  • Singulation (depaneling)
  • Coverlay patterning

• Talon^® Nanosecond Lasers: superior combination of performance, reliability and cost.
• Talon^® Ace™ Laser: highest single-mode ns UV power in the industry, with TimeShift programmable pulse capability
• IceFyre^® Picosecond Lasers: exceptional performance and unprecedented versatility at industry-leading cost-performance

	Talon	Talon Ace	IceFyre
Wavelengths	UV or Green	UV	UV
Power	UV: Up to >45 W Green: Up to >70 W	>100 W	Up to >50 W
Pulse Width	UV: <25 or 40 ns Green: <25 or 43 ns	<2 to >50 ns	<12 ps (10 ps typical)
Repetition Rates	0 to 500 kHz	Single shot to 5 MHz	Single Shot to 10 MHz
Max Pulse Energy	UV: Up to >500 µJ Green: Up to 1000 µJ	Up to >500 µJ	Up to >60 µJ
Other Features	Laser/controller in single, compact package 24/7 industrial reliability E-Pulse™ technology for superb stability	24/7 industrial reliability TimeShift™ technology for pulse control Laser/controller in single, compact package	24/7 industrial reliability TimeShift™ technology for pulse control Laser/controller in single, compact package

Presented here is a summary of recommended lasers for various flexible PCB manufacturing applications. Please use this as a reference guide only, and always contact us to discuss your application and requirements in detail so that we may provide the best solution for you. 

Even with the advantages that lasers have over traditional tools, laser systems can still degrade over time. Some causes of degradation include thermal effects on a laser system’s internal components, vibrations or shock and debris near the processing site. These issues could affect laser performance in a number of ways. First, output power may be reduced, causing the laser to be less efficient. Another problem that may be caused is a change in the focus or other profile of the beam, which may lead to a cut or drill to be off target, too deep, low quality or possibly damaging to another part of the material.

Therefore, to ensure the highest quality flexible printed circuits manufacturing and to minimize the possibility of production down-time, it is crucial to monitor the laser beam frequently with appropriate instruments–like Ophir^® power sensors, power meters and beam profilers–that can operate at the laser’s wavelength while handling its maximum output power level.

• Thermal Effects
• Debris from Process
• Vibrations and Shock

There are three types of beam analysis instruments to monitor your laser: (1) sensors and detectors to measure power, (2) power meters to process the information provided by sensors and (3) beam profilers to determine focus position and other beam characteristics. Shown below are the main criteria for choosing such instruments.

• Compatible with laser wavelength
• Power/energy range/density
• Beam size
• Calibrated power measurement

• Compatible with sensor
• Connect to system/PC
• Track process data over time
• Compare multiple measurements at once

• Measurement of multiple attributes
  • Focal shift
  • Focal spot size
  • Laser power and power density
  • Changes over time
  • Laser propagation characteristics
• Speed of measurement

Laser Power Sensors

MKS offers a comprehensive portfolio of Ophir^® laser thermal power sensors, several of which can measure the optical output power of short- and ultrashort-pulsed lasers such as IceFyre, Talon, Talon Ace and Quasar. These sensors have a very high damage threshold to withstand the high optical peak power delivered by each pulse. Ophir sensors and meters meet the ISO/IEC 17025 standard for calibrated devices.

• Laser Thermal Power Thermal Sensors: very high damage thresholds for hundreds of watts power measurement.

	F150(200)A-CM-16	30(150)A-SV-17	F80(120)A-CM-17
Spectral Range	0.248-9.4 µm	0.19-11 µm	0.248-9.4 µm
Power Range	300 mW - 200 W	100 mW - 150 W	100 mW - 120 W
Energy Range	50 mJ – 200 J	50 mJ – 300 J	50 mJ – 200 J
Max Avg Power Density	35 kW/cm2	60 kW/cm2	35 kW/cm2
Max Energy Density (2 msec)	45 J/cm2	50 J/cm2	45 J/cm2
Aperture	Ø16 mm	Ø17 mm	Ø17.5 mm
Response Time	3 sec	1.7 sec	2 sec
Other Features	Not water-cooled

Power Meters

Ophir laser power and energy meters work on the smart plug principle. This means that almost any power meter can work – plug and play – with almost any of the wide range of Ophir optical sensors.