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Supplementing your production capabilities with flexible circuit laser processing can pay big dividends. It not only enables you to broaden the set of services you can offer your customers, but it also extends your reach into additional markets you might not otherwise be equipped to serve. Employing laser technology is one of the best ways to stay current in PCB processing. It’s an enabling technology that lets you process more—and smaller—features faster and more accurately than what is possible using mechanical processing.
In the previous installments of the “Stepping Up to Laser Processing for Flex” series we’ve addressed topics such as what to look for in a flex PCB laser processing system, an overview of flex laser systems, cost of ownership issues and a comparison of various process development strategies. In this sixth and final installment, we will look at the ongoing maintenance and upkeep of your system. It is not meant as an exhaustive overview of required maintenance, but addresses several best practices related to the proper care and feeding of your system; detailing some of the reasons for what might seem like arcane or unnecessary activities to those who are new to flex laser processing. You should always refer to the maintenance documents provided by your system supplier for a full and accurate picture of the required and recommended maintenance activities for your specific systems.
Maintenance Should Not Be an Afterthought
Today’s maintenance managers are constantly managing the trade-offs between higher machine availability (asset utilization) and lower maintenance costs (cost control). In their balancing and prioritizing of these competing concerns, they need to consider such factors as maintaining aggressive production schedules, the level of investment in capital equipment, safety and health concerns, and environmental regulations. And to make everything work, they need to ensure availability of properly-trained technicians, spare parts and tools (resource allocation).
Although it’s exciting to get your new flex laser processing system installed and processing panels, you shouldn’t wait until you are up and running before you turn your attention to the topic of system maintenance and upkeep. Planning for ongoing maintenance should be a priority. If this is your first foray into laser processing, keep in mind that, although many general maintenance concepts are shared with mechanical-based systems, there are maintenance needs that are unique to laser-based systems.
Having the proper maintenance mindset from the beginning will ensure that your laser systems continue to safely and effectively deliver the performance you require and the longevity you expect, thus maximizing their lifetime value and return on investment.
Scheduled Downtime vs. Unplanned Downtime
Your preventive maintenance schedule should include planned downtime to check, clean, adjust, and/or calibrate the subsystems of your laser system as per the manufacturer’s recommendations. Having the machine scheduled to be off-line for a short period during preventive maintenance will not only make sure that the maintenance is performed, but will also help minimize any unplanned processing disruptions and maximize the system’s future uptime. This is especially important when interventions require support from the system manufacturer’s off-site service engineers.
As with most production equipment, the costs associated with the extended unplanned downtime or degraded performance of your laser systems can be a multiple of the costs spent on maintenance. That multiple can very high when one looks beyond decreased system efficiency to the loss of productivity and the associated scheduling and yield impact on downstream processes.
There are also situations when preventive maintenance and scheduled downtime may need to be more frequent. If your application involves more debris-intensive processes—such as large through-holes or routing—or if you are operating your systems in a less-than-optimal environment, maintenance frequency should be adjusted accordingly. Similarly, operating your systems 24/7 for extended periods of time will dictate more frequent planned maintenance. Finally, more challenging applications with more strict quality controls and yield requirements will also dictate an accelerated maintenance schedule. This situational or process-dependent maintenance planning will help ensure that your system is delivering the level of performance and precision you need for such applications.
In an environment where equipment replacement costs continue to rise, proactive preventive maintenance is an easy way to extend the equipment lifecycle of your flex systems. This extension of your systems’ service life better positions you to postpone or defer budgetary issues associated with capital outlays for new systems.
UV Laser System Preventive Maintenance Overview
Your laser-based flex systems have a unique set of maintenance requirements. In addition to proper operator training—to reduce system downtime related to misuse—it’s important to follow a scheduled maintenance regimen in order to run at peak efficiency. This generally includes caring for and updating calibrations of the laser and optics subsystems and beam positioning subsystems, maintenance of the cooling and pneumatic subsystems, general system cleaning and a variety of other activities specific to your system. Regular system performance validation tests can also become a useful component of your preventive maintenance system. These tests can preemptively identify system issues that might affect production yield and should be built into your process flow.
Laser and Optics Subsystems
To maintain high-quality, high-yield via formation it’s important to minimize the presence of contaminants that can come into contact with the optics, including mirrors, beam expanders, galvanometers, scan lens, etc. These are the components that transmit, deflect and shape the laser beam. Proper calibration of the laser power, along with the removal of contaminants from the optics path, will help ensure that the system delivers the desired laser power, spot size and spot quality. In some circumstances, checking the alignment of elements in the optics path is also necessary to ensure that the laser is providing the spot size and quality required for high-quality via formation and delivering maximum yields.
Beam Positioning Subsystems
The precise, coordinated motion of a number of beam positioning components such as linear stages, galvanometers, and more advanced components is necessary for your flex system to precisely position the laser beam and provide optimal process productivity and quality.
As with any piece of equipment that has moving parts, periodic cleaning and lubrication will keep things moving smoothly. Flex laser processing systems are no different. Depending on your shop floor’s environment, the materials being processed and the application you are running, this could mean more frequent maintenance actions are necessary. Scheduled maintenance should include the cleaning and lubrication of the x and y stages, and the removal of any debris that can affect the smooth operation and motion of the components.
Beam positioning subsystems such as the galvanometers and related vision subsystems may also require periodic tuning/recalibration to ensure optimum performance and accuracy.
Pneumatic Subsystems
Most laser systems include some level of pneumatic subsystems. These are used for functions such as providing the sensitive optics with pressurized clean air to avoid debris contamination, aiding debris removal during processing, actuating doors, etc. To ensure optimal performance of these functions, it is typically recommended to check pressure and/or flow, clean the air dryers and water/oil separators, and clean or replace any clogged filters.
Cooling Subsystems
A typical UV laser system used for flex circuit processing will include a laser chiller, various fans and possibly other cooling mechanisms. The performance of these cooling components is crucial to maintaining the laser power, beam quality and pointing stable. It also extends the longevity and performance of the system’s other components.
To keep the laser at the optimum temperature for stable performance, most laser systems include a self-contained recirculating chiller. For such recirculating chillers, the level of fluid (generally water) must be maintained at the recommended level. Water will build up algae and other particulates over time. Thus, to avoid blockages from restricting flow and causing temperature and pressure spikes from damaging the laser or reducing its performance, it is important to replace the water at the manufacturer-recommended intervals and—if specified—add algaecides and anticorrosive additives to the water.
System fans, especially in poor environmental conditions, will build up dust that must be removed by vacuum to ensure effective operation and longevity.
General Cleaning
It may seem obvious that sensitive, high-value applications such as flex PCB processing and their processing systems would benefit from clean processing areas. However, not all operators pay close attention to such cleaning. Periodic vacuuming of the processing bay and work table, and even regularly checking the debris vacuum lines for debris build-up is a quick but high-value activity.
Regular System Performance Validation Tests
While typically not required by some system manufacturers, regular verification of process quality for one or more well-characterized processes, critical system calibrations, laser power statistics and other leading indicators of potential system issues can become a powerful tool for getting ahead of unscheduled downtime, quality and yield issues.
Importance of Operating Environment
In a previous column, we discussed the importance of maintaining the proper operating environment for your flex system. Refer to that column for a refresher on topics such as the proper temperature range, power requirements, access to water for cooling, air filtration, etc. Obviously, if you are operating your laser systems near environmental pollutants or the airborne byproducts of adjacent manufacturing/processing you’ll need to adjust your maintenance schedule accordingly. If the current environment does not meet the system’s site requirements, place a high priority on improving the conditions or consider relocating your systems to a less challenging operating environment.
Laser Safety
If you are new to laser processing, laser safety is something you’ll need to be prepared for. Take the time to familiarize yourself with the safety guidelines provided by your system supplier. Also, refer to the previous column on laser safety. While operating and performing maintenance on the system, you should make sure that proper safety guidelines are in place and that operators and maintenance personnel are properly trained. If servicing the laser system with the laser on, protective eyewear rated for the laser in use is a must. For the protection of others, sufficient, appropriately-rated laser safety panels must be used during such service activities. Consult the operating guide and safety information that came with your system, and follow the guidelines suggested in the guide.
Partnering With Your Supplier
Your system supplier will typically provide a comprehensive preventive maintenance guide, which lists maintenance checks, describes the suggested maintenance processes and lays out appropriate maintenance intervals. Although it sometimes assumes a lower priority, documenting preventive maintenance and keeping an up-to-date maintenance log, together with the system-generated log, will ensure that potential problems are identified before they impact your processing operation. Also, documenting service issues unique to each system helps give your supplier’s service organization a more accurate assessment of your systems’ condition over time.
Summary
In this article, we have discussed flex PCB laser processing systems and addressed some of the maintenance topics that are unique to those systems. Proactive preventive maintenance plays a significant role in minimizing production disruptions, extending the equipment life cycle of your flex systems, and maximizing the value that can be extracted from those systems. Since these systems represent a substantial investment in capital equipment on your production floor, extending their useful life, as well as ensuring their efficient and effective operation, should be a high priority. We invite you to review previous installments in this series for other information regarding flex PCB laser processing. The series is a useful guide with actionable information for considering the addition of flex laser processing into your production environment.
Patrick Riechel is product manager for ESI’s flexible circuit micromachining tools. To read past columns by ESI, or to contact the author, click here.
