Defect Mitigation and Product Quality: Five Areas to Watch

Transcription

1 Defect Mitigation and Product Quality: Five Areas to Watch

2 By Chris Eldred Defect Mitigation and Product Quality: Five Areas to Watch One of the reason the label quality control fell out of favor in the 80s was the emphasis it placed on inspecting defects out rather than eliminating the opportunity for defects to occur. In a perfect world, product designs and manufacturing processes can be perfectly fine-tuned to eliminate most defect opportunities. Unfortunately, shortened design cycles, difficult-to-modify product qualification processes and low product volumes often limit the amount of fine-tuning that can be done as defect opportunities are found in production. One of the key points of value an electronics contract manufacturing partner can add is the ability to mitigate defect opportunities both through design for manufacturability (DFM) and through robust process control. TeligentEMS, an EMS provided headquartered in Havana, FL, routinely supports mission critical projects and focuses on mitigating defect opportunities wherever possible. This whitepaper looks at five areas that it considers important in mitigating defect opportunities both through redesign, and via exceptionbased systems and process controls. These are: New product introduction (NPI) practices Specialized application expertise Supply chain management support Documentation control centralization Ability to monitor quality trends in real-time. NPI Practices The NPI process is the first step in defect mitigation because it is the point at which a contract manufacturer analyzes the product and determines what challenges it may present. In TeligentEMS process at customer request, DFX including design for manufacturability, assembly and testability (DFM/DFA/DFT) can be performed to eliminate issues likely to contribute to defects and ensure an optimized inspection and test process. This includes a comparison to industry-standard design guidelines, plus analysis of any equipment constraint issues that may need to be addressed based on a customer s preferred production methods. TeligentEMS team also validates all parts against the approved vendor list (AVL) and verifies RoHS status. Following prototype and pre-production runs, customers are provided with detailed feedback on lessons learned. This feedback phase is important. In some cases, this feedback may help improve a product design by illustrating the production impact if the design is left unchanged. In cases where requalification costs prohibit changes, it provides an improvement suggestion for the next generation plus documents specific process constraints.

3 Specialized Application Expertise Most contract manufacturer-driven DFM processes utilize industry-standard design guidelines as the basis of recommendations for change. However, there may be unique DFM requirements that are not considered if the contract manufacturer lacks expertise in that application. TeligentEMS has long specialized in RF communications-related products and frequently encounters process and designrelated issues not commonly addressed by industry-standard design guidelines. For example, to minimize signal noise in the printed circuit board assembly (PCBA), solder paste deposition needs to be exceptionally even. At the manufacturing level, this translates to consistent solder joint height, wetting angles and volume. At the design level, that is determined by pad geometry and solder mask clearance design. In some cases, the best option for maintaining tight tolerances is done through solder mask opening design and in other cases it is done with etch design. However, if too large an amount of copper is exposed, the potential for solder deposition variance and concomitant electrical noise increases. A common example of this issue involves SMT connectors that have a center joint which provides a signal. If solder paste height and wetting is not even, the signal is distorted. Having an EMS provider with RF expertise engaged early in the design process is critical, because once the signals are set, modifying the design forces the design team to effectively rework their entire layout process. Similarly, once FCC testing is completed, it becomes difficult to cost justify another design spin based on manufacturability requirements alone. Another point of unacceptable variance can occur when the cumulative geometric dimension tolerance creates an unacceptable level of electrical noise. This can occur when components with fairly broad spacing tolerances exceed the total placement tolerance on the board. This can be mitigated through solder mask design to constrain movement and lock components in place. This example also underscores the value of having design engineers perform a geometric dimensioning and tolerance check after component selection. When the issue isn t discovered until manufacturing, often the only solution is to add special fixturing to lock the components more tightly in place during reflow. This increases production tooling non-recurring engineering expense. As these two examples illustrate, the solution to application-specific manufacturability issues is rarely one-size-fits all. Instead, it is requires considering multiple trade-offs and choosing the solution that best fits the product requirements. Supply Chain Management Support Supply Chain Management expertise is also important in defect mitigation since supplier quality, materials integrity and handling practices all have an impact on quality. To ensure materials integrity, TeligentEMS utilizes a proprietary system known as Possible-X, which integrates closely with the ERP system in receiving. The receiving inspection process has been designed to capture the bulk of the information required for both internal and customer requirements so that this information travels with the material throughout the storage, kitting and production process.

4 Upon delivery each component is validated to the AVL. Any variance in labeling triggers additional inspection steps. Custom components are automatically routed to go through additional inspection including Critical-to-Quality (CTQ) measurements. Following inspection, a bar code label with purchase order receipt information is generated for each package and an ERP transaction is executed. The label data includes key information such as moisture sensitivity level (MSL), RoHS status, etc. Certificates of compliance are also validated at that point and scanned into Possible-X. The system automatically flags parts needed to fill shortages to ensure they are expedited. Possible-X supports TeligentEMS robust process for counterfeit prevention a design that conforms to AS5553 and the Company also maintains membership in the Government-Industry Data Exchange Program (GIDEP), to ensure that process includes checks for identified trends in counterfeiting. Documentation Control Centralization Products and manufacturing processes often go through engineering and/or process revisions. As a result, centralized documentation control is critical in ensuring the correct revision level of the product is built and all known issues are addressed by the production process. As the central digital repository for information, Possible-X is the access point for all production documentation and links all related information. It tracks ECOs and deviations and links them to work orders so that as documentation is pulled to build a product, production associates access the correct revision. Possible-X also contains a new production introduction (NPI) checklist and work instructions for each product. The checklist aligns with the Company s focus on Lean manufacturing since a standardized setup process helps minimize variability. This is particularly important with low volume and/or legacy builds as production on these products is typically infrequent and there may be little production floor memory of production setup. Production associates utilize Possible-X s Production Dashboard, known as p-dash. This tool is designed to help empower production associates by ensuring they have fast access to the information needed to do their jobs. Associates must log in using their id number. They utilize the system to clock in and out, plus access all documentation related to their jobs, which is typically displayed at workstation monitors. p-dash also facilitates movement of cross-trained associates among different work areas as demand varies, since documentation access is linked to work order. This login access supports both intellectual property protection and ITAR compliance. p-dash also lets associates open support tickets which text a message to an engineer whenever a production issue arises that the associate needs help with. This helps ensure that issues that could impact product quality are corrected immediately.

5 Ability to Monitor Quality Trends Real-Time The fifth area of focus in real-time quality trends tracking. While the data generated is derived from inspection activities, showing this data in real-time helps drive a rapid response in identifying and eliminating defect opportunities as they occur. At TeligentEMS, Possible-X s metrics menu has been designed to provide early warning when product quality is falling outside of control limits and facilitate rapid root cause analysis and corrective action. Defects per million opportunities (DPMO) is monitored in the SMT area in real time. Monitors showing a real-time, color coded graphical interface indicating both DPMO and production status relative to production targets are placed throughout the production floor and are also accessible to management. DPMO is measured in real time and the charts displayed on monitors show averages of the last hour, previous 24 hours and previous 7 days. The top ten identified defects are shown in a pareto diagram. A test data collection chart displays results from in-circuit test, functional, flying probe, RF, burn-in and hipot, making it easy to identify if any issues are developing in any test stage. Issues are addressed as they arise by the people closest to the issue. As with all Possible-X tools, it is possible to drill down to data related to specific work orders and serial numbers to determine the root cause of any identified issues. Mitigating defect opportunities is best done with a holistic approach that considers the complete product realization process. The ideal time to integrate a contract manufacturer is early enough in the design phase that common manufacturability and testability challenges can be discussed and corrected. However, defect opportunities are also caused by non-production activities. Utilizing systems which ensure material integrity, correct handling and use of the correct documentation revision level eliminates defects that can creep in through inattention. Use of an NPI checklist with each production run helps eliminate setup variation and ensures that any known product issues are monitored even if the product is built infrequently. Finally, real-time monitoring of quality data trends helps ensure that variations in product quality caused by undetectable variations in material quality or a process variation are rapidly identified and corrected. Chris Eldred is TeligentEMS President and CEO. He can be reached at celdred@teligentems.com. About TeligentEMS For more than 30 years, TeligentEMS has provided a full range of electronic manufacturing services to companies in the industrial, medical, military/aerospace, telecommunications and instrumentation industries. We specialize in technically complex printed circuit board assemblies, subassemblies and box build. Our superior RF expertise enables us to support a wide range of communication technologies. We are ITAR registered and ISO 9001 and ISO certified. Our global procurement and supply chain capabilities, combined with our real-time systems for project status, quality data collection and device history recordkeeping ensure we offer customers a cost effective and highly responsive solution.