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STEP 2: Process Control
December 31, 1969 |Estimated reading time: 9 minutes
Cost and quality optimization in surface mount device (SMD) production requires a holistic manufacturing approach. Today, relevant progress can be achieved only if production lines and supply chains are taken into account in their entirety. The process engineer’s work and the use of specialized tools are becoming more important.
By Vern Harrison, Douglas Johnson, and Stefan Zuehlke
These days, cost and quality optimization in SMD production requires an approach that looks at the whole manufacturing process. Making improvements to individual machines and selected internal processes may have been sufficient in the past, but today relevant progress can only be achieved if production lines and supply chains are taken into account in their entirety - ranging from suppliers to customers. The work of the process engineer and the use of specialized tools are becoming more important every day.
Process engineers don’t like to hear this, but their job traditionally has consisted of providing in-house troubleshooting services and responding to emergencies. They get called when inexplicable problems arise, when the scrap rate skyrockets mysteriously, or when quality and efficiency indices drop. In most companies, their role has not changed to this day.
In modern SMD manufacturing, however, things are starting to change. Tough price competition is forcing companies to attack and fix process problems proactively. Rapid technical process in the electronics field also demands permanent process changes. Examples include the introduction of ever smaller (0201s and 01005s) and more sophisticated (μBGA) components, or environmentally friendly processes such as lead-free soldering. In safety-relevant fields such as the automobile or medical-equipment industries, legal product reliability requirements call for the implementation of more complex and comprehensive tracing and tracking systems.
In all these cases, changes affect not just individual machines or internal subprocesses. Instead, the entire manufacturing process - including the selection, procurement, and storage of components - must be modified and adapted. Because companies can no longer afford the traditional trial-and-error approach, the traditional process engineer’s role in electronics manufacturing is undergoing a transformation.
Processes with Predictable Costs and Quality
The process engineer’s main job will continue to consist of preparing, implementing, and monitoring manufacturing processes. But these requirements are getting more demanding. Today’s process engineer must be able to define or predict the results of these process changes on key performance indicators accurately before they are implemented.
To perform these tasks successfully, the classic qualifications of a process engineer must be expanded and enhanced. In addition to a pronounced desire for improvements, high-solution orientation, openness, and team skills, process engineering jobs demand managerial qualities and proactive planning skills, as well as pronounced analytical skills and knowledge of statistical process control (SPC) techniques.
The Arsenal of Weapons Grows
While demands on process engineering are on the rise, available tools are also improving. Recording and collecting data, which had taken a lot of time in the past, now is done by modern machines and tools automatically. Steadily improving programs and utilities help with the analysis of large data volumes and monitor the most important process parameters automatically. When subprocesses change, these tools can calculate the effect of such changes on the overall process in seconds. The engineer can reduce the need for the classic trial-and-error methodology on the line by simulating new processes offline with data models and scenario techniques.
Tools for All Phases of Product Lifecycle
Product definition. Leading technology suppliers recognized early that process engineering will become an increasingly important factor for the competitiveness of its customers. Some of today’s innovative placement machines offer many software modules and system solutions that let process engineers design, control, and monitor their SMT processes across multiple lines. One of the most critical prerequisites is that machines share the same software and data structure, and feature open interfaces to other systems. The process engineer’s work is made significantly easier through software functions that correspond to specific requirements of each individual product lifecycle phase.
At the product definition level, this approach starts with the new product introduction (NPI). Creating setup and placement programs with perfect preparation by the board developer is virtually trouble-free: CAD data and the bill of materials (BOM) can be read-in automatically and translated into machine programs and setup instructions. But what happens when only a sample board is supplied? With software,* the programmer can use overlay techniques to drag-and-drop and align appropriate components from libraries on a scanned-in image of the sample board. The software creates the placement program automatically as well as BOMs in the background. Afterward, any missing or misaligned components can be searched using the software’s help function while remaining offline.
Figure 1. Before and during NPI, eight individual process steps are clearly defined. Within these processes and with the right programming software solution and tools, there is potential for cost savings.
This NPI process provides many benefits for the electronics manufacturer. Instead of tying up machines or dedicated NPI lines with long tests and run-ins, most of the work occurs offline. The software-based board inspection accelerates the startup phase and provides a high level of efficiency from first yield. Each change performed in the software is reflected in the process documentation automatically. At the same time, the user can define process parameters, tolerances, and limit values that will be monitored and checked later by machine programs.
Once placement and setup programs have been tested offline, they can be downloaded directly to the line. The traditional requirement to teach each machine manually is eliminated.
Ramp-up and Maturity Phase
Engineering data management (EDM) is a powerful tool for managing production data. EDM combines the advantages of central, multi-line data management with the ability to change programs on the line. The result is rapid ramp-ups. All changes made on the line are recorded, documented, commented, and forwarded automatically to the master data management system. The decision of whether or not these changes should be added to the central database is made in the EDM’s clearing pool. A version history and control system make it possible to track this process, make any corrections, and restrict them to specific machines. As the data is moved from the master database, special templates on the lines define which parts of the placement data and setup program will be line-specific, and which will be master-specific for each product. This way, the system ensures that any program changes resulting from engineering change requests (ECRs) are replicated reliably to all lines, and that their execution is not left to accident.
Production scheduling. Features like these, which make processes more secure and reliable, are precisely what process engineers need for this work. Setup-center software provides even more benefits. This software option enforces barcode-based component verification not only during product changeovers, but also each time components have to be refilled and spliced-on during running production. At the same time, the software helps the operating staff to monitor fill levels at the machines while ensuring optimized and process-conforming reel changes.
Figure 2. Managing state-of-the-art line-capability changeover has evolved from heavy, module-based changeover, requiring multiple personnel, to an intelligent (and rapid) software-driven changeover. Using current integrated software tools, production orders can be dispatched to capable production processes quickly and effectively.
Once the ramp-up has been completed, the process engineer begins the continuous improvement process. Again, the right software can provide invaluable help. Machine reports provide information with almost any selectable level of detail and depth. If, for example, the scrap trend at the corporate, line, or shift level gives cause to suspect that a process flaw may be at fault, the process engineer can analyze the data down to the machine or batch level. The engineer also can find out if any process modifications create the desired results or cause unwanted effects in other places.
Lastly, time-consuming management and KPI reports can be almost completely automated. The software not only eliminates errors and improves the reports’ objectivity, it allows the process engineer to spend less time crunching numbers and more time doing what he does best -analyzing and improving processes.
Maintenance and Phase-out
During this phase of the lifecycle, the process engineer uses the same tools, but process monitoring and reporting will be mostly automated. Regular reports are increasingly becoming customized for specific target groups (operators, supervisors, management, quality control, etc.), and are designed predominantly as trend reports.
Phase-out involves removal of inactive data from the operational systems to free-up capacity for new data and improve the systems’ performance. It’s important, however, to make sure that this data can be reactivated at any time. For example, historical data can be useful to accelerate the creation of stable processes for new products.
Positive Outlook
SMT process engineers can rejoice about two positive trends. On one hand, their work is becoming more critical for their companies’ profitability. Their job focuses on improving the factors that determine a company’s competitiveness - namely the cost, quality, efficiency, and flexibility of the entire electronics manufacturing process.
On the other hand, machine manufacturers increasingly recognize and support this trend with appropriate tools. Development activities reflect major trends of the future: Web-based tools and software modules will provide access to processes and control data at any time and from anywhere. As a result, using optimization specialists will become more efficient and cost-effective because they will be able to monitor and control processes in factories remotely.
At the same time, Web-capable software makes it possible to link previously separate process chains. For example, a machine manufacturer’s service staff will be able to access systems remotely to check the machines’ condition and improve scheduled maintenance intervals. At the same time, counters on the placement machines could be linked to the purchasing department directly, or even to the supplier’s ordering system.
Conclusion
The rising demand for traceability also provides a strong impulse for integrating SMT processes with manufacturing execution systems (MES) and enterprise resource planning (ERP) systems. Here, the process engineer’s job is to provide the appropriate process-technological foundation during the NPI phase, especially as far as the desired level of accuracy is concerned. By combining setup verification with specific barcode IDs on PCBs, some technologies* can supply all the data required for reliable product and component tracking. This data can be transmitted to higher-level systems easily using open XML interfaces.
Real-time is another core idea for future developments. Systems and software will increasingly process and supply data in real-time to accelerate response times at all levels. It will be up to the process engineer to aggregate this flood of data into manageable and informative packages, and present them in a way that makes sense for specific users.
*SIPLACE platform, Siemens.
Vern Harrison, software product manager, Siemens AG Automation and Drives, Electronic Assembly Systems may be contacted via e-mail: Vern.Harrison@siemens.com. Douglas Johnson, software product manager, Siemens AG Automation and Drives, Electronic Assembly Systems, may be contacted via e-mail: Douglas.Johnson@siemens.com. Stefan Zuehlke, software product manager, Siemens AG Automation and Drives, Electronic Assembly Systems, may be contacted via e-mail: Stefan.Zuehlk@siemens.com.