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32 DESIGN007 MAGAZINE I MARCH 2024 Changing the order of production or the time allotted for a task creates variation. Changes to temperature in the facility or concentration levels in chemical processes also might affect the output. Bringing it All Together for Ongoing Improvement I encourage you to visit your preferred man- ufacturer to get a better feel for how they make boards and where variations are most likely to occur. With a good working knowledge of how the manufacturing process can dri and vary, potential issues can be anticipated and addressed in the design phase. Understanding the fabrication process will help you align the PCB manufacturer's capa- bilities with the design requirements. Collab- orating with them before creating the design can help ensure that elements like component placement are optimized for manufacturabil- ity. is can save time and effort and help real- ize a more manufacturable design. ere is so much more to explore on the sub- ject of designing for reality. I hope you will lis- ten to our Episode 2 that dives into electronics pre-manufacturing processes. DESIGN007 Matt Stevenson is vice presi- dent and general manager of ASC Sunstone Circuits. To read past columns, click here. Down- load The Printed Circuit Design- er's Guide to… Designing for Reality by Matt Stevenson. You can view other titles in the I-007eBooks library. An important but sometimes overlooked aspect of flex and rigid-flex fabrication and assembly is the flex circuit tail, which is attached to a rigid PCB with pressure-sensitive conductive adhesives. This sub- assembly is becoming very common. We often see this applied to glass displays and microelectronic applications. But this method of attachment without connec- tors is not as straightforward as one may think. The wide varieties of circuitry to be bonded create many attachment challenges. The best track configuration is not always pos- sible, so one must be familiar with the optimum lay- outs as well as what is not recommended when con- sidering these trade-offs. Less than optimum trace and pad layouts result in the need for more custom- ization and smaller processing window variations for the bonding process. Here are some common configurations that flex assemblers have developed, and the preferred approach for the method of bonding. Bonding imbalance results from either bad co-pla- narity between the bonder head and stage or a thickness deviation of the flex and PCB materials. The interposer will absorb these discrepancies to some extent and help bring the bonding results in parallel. If bonding is imbalanced, the devel- oped color will also be uneven; adjust the bonder tool or stage until you achieve uniformity of color. Since Prescale will turn color with heat and pressure, con- firm the color in short bonding time and low pressure. To confirm the condition of equipment, please do not use cushion materials. Continue reading in the February 2024 issue of Design007 Magazine. Design Guidelines for Flexible Printed Circuits