Lean Manufacturing for Rigid Flex PCB

The common part number startup for Rigid Flex PCB often can suffer from a number of those wastages. Particular waste items are specific to a part number (customer out of office, conflicts in documentation, iterative design discussions, etc.) or be implanted as accepted gaps in a supplier's product launch system. As part of a continuous enhancement mentality, wastes should be identified for reduction through a documented and tracked part number introduction procedure.

Some of the more common waste elements are:

- Transport
- Inventory
- Motion
- Waiting
- Over-processing
- Over-production
- Defects

Transport: In a new part number introduction process (NPIP), transport is the movement of documentation (electronic or paper) from one department to another requiring successive reviews and sign-offs. Excess transport is a symptom of a departmentalized approach to part number start-up rather than a process flow approach. A cross-functional design review team with one leader can help and remove departmental barriers assure that reviews and inputs are done in parallel rather than serially. Transport can also include sending info requests and approvals to clients and providers. These demands need to be challenged relating to their effectiveness and necessity.

Waiting: New part number start-up requires information flow. When someone is waiting for information, oftentimes the process becomes stalled at various steps. This can happen from within the company, the customer, or the supplier. A good NPIP system includes checklists so the needed certification is quickly identified and missing components can be requested immediately. Team members are focused on quick communication so that there is as little standing by time as possible. Customers, inner team members, and suppliers all need to be intimately involved to foster good communication. Again, parallel processing is an important message. Sometimes a decision followed by a course correction, is a faster journey to the destination than waiting for all the information to become available.

Over-processing: In the design and kick off start-up system, the equivalent of over-processing is over-specification. It is appealing to specify a tighter resistance than required because developers believe it provides them a bigger safety margin. While this is sometimes the case, other times a tighter tolerance will push a manufacturer to make tradeoffs that reduce producing yields, require additional tooling, and add time to the processing sequence. When permission standards are defined in absolute terms, additional delays occur. Criteria specifying "no stains" or "no foreign material" can create an inspection struggle until a conference of the minds occurs between the customer and supplier. Having a well-documented layout and design guide, as well as having knowledgeable manufacturing technicians on the startup team, will help assure that a new part number kick off with acceptable manufacturing yields and meets the customer's requirements.

Over-production: The matching of overproduction in a part number startup system is over-design. As in the case explained in overprocessing, developing in "safety margins" might be preferable, but it can also backfire. An example in the world of flexible circuitry might be specifying thicker copper to permit much higher amperage capability, but thicker copper can also degrade flexibility. Over-design may also increase cost, so one needs to understand if the increased cost truly yields a more reliable product.

Defects: The outcome of a poorly performed part number introduction may result in low manufacturing yields triggering high scrap rates, delayed deliveries and potentially malfunctioning product supplied to the customer. A startup process should be rigorous enough to prevent pitfalls seen on previous part numbers. It's not possible to get everyone review every part number prior to product launch, but using multiple subject matter professionals to preview design layouts is a good first step. Capturing the cooperative wisdom of the organization is the goal as this can guide identify "gotchas" that can be prevented. This review should be considered an aggressive step but in the world of custom made flexible circuits and heaters even the best plans may result in surprises. When this happens, a team focused on quick reaction is critical. When the gremlins unavoidably are revealed, the best NPIP system is a combination of pre-launch proactive review and a reactive team ready to respond quickly.
It is a continuous improvement effort plan to supply intensified customer support during initial part number design and delivery. It is a methodology tailored to a company that provides custom engineered products. Similar techniques and practices can help reduce the mudas experienced during part number startup.