Design007 Magazine

100 DESIGN007 MAGAZINE I DECEMBER 2021 e use of rigid-flex PCB, CoB implemen- tation, and wirebonding alone could lead to a slew of potential pitfalls or challenges: • Designing the rigid-flex with different stack-up between the rigid and flex sections • Wirebond routing in the miniature board area • Use of stacked vias for routing • Controlling the impedance of 100 Ohm • Extraction of the 3D wirebond in 2D (with all legacy tools) does not help with accuracy • Simulation time for extracting the wirebond profile with respective signals e CoB assembly process, commonly referred to as direct chip attachment (DCA) technology, refers to the assembly/technology process in which a die is directly mounted, elec- trically connected, and typically encapsulated with a silicone- or epoxy-based material in the final PCB. Figure 2 shows a typical implemen- tation of the CoB and the wirebonding. e rigid-flex design is best created using a PCB design tool with the ability to define and add multi-stackup and constraints for rigid- flex, including inter-layer and comprehensive spacing rules. When the CoB is a large chip with a greater number of pins than a typical PCB tool can handle, you will need to use the SiP capability of a package design tool. Figure 2 and Figure 3 show the final fabrica- tion layout images of the product and 3D view with wirebond profile. Aer the layout of the CoB in rigid-flex, cre- ate the MIPI/xTalk channel topology and per- form signal extraction and simulation of the channel. If a custom compliance kit/MIPI is available, perform compliance checks and gen- erate the compliance signoff pass/fail report. All of these are best performed using a fast extraction and simulation solution. Next, it is important to simulate the entire camera module including the rigid-flex, wire- bonding, channel, and the connector. is is typically done using the divide and conquer approach by extracting each component as a whole or in parts and merging them together manually in a SPICE file for simulation. is is no longer true with new extraction tools, which can extract the rigid-flex board, wire- Figure 2: Fabrication drawing.

• December 2021 — Design007 Magazine
• Feature Contents — The Art and Science of PCB Design
• Additional Contents
• Flex007 Contents
• Column — The Art of PCB Design: I Know It When I See It
• Feature Interview — PCB Design: Where Art and Science Intersect
• Column — 'Dealing' With PCB Design
• Feature Article — Will AI Replace the Art of PCB Design?
• Column — The Rise of Resin in IoT Applications
• Column — Leveraging Digital Twins to Optimize Electronic Systems
• Feature Interview — Field of Dreams: The Art and Science of Designing with Field Theory
• Article — Test and Inspection
• Feature Article — The Colorful World of PCB Design
• PCB007 Highlights
• Feature Article — The Art of Using Symmetry—and Asymmetry—in PCB Design
• Column — Best Practices for Solder Mask Application
• Column — High-Performance 3D Printed Circuitry
• Feature Interview — The Art and Science of DFM
• Feature Interview — The Art and Science of PCB Design—You Are the Best Tool
• Feature Column — Creative Minds Pushing Boundaries
• MilAero007 Highlights
• Column — Live or via Zoom, Knowledge Is All Around Us
• Column — Better Electronics Start With Better Training
• Short — Navigating the Supply Chain Storm With ICAPE
• Article — RealTime with… American Standard Circuits: Thermal Management
• Feature Article — Revving Up Design
• Flex007 Column — Shaping Flexible Circuits
• Flex007 Short — Elementary, Mr. Watson: We've Never Done It That Way Before
• Flex007 Highlights
• Flex007 Column — Challenges in Simulating a Wirebonded CoB on a Rigid-Flex PCB
• Flex007 Short — Flexible, Wearable X-ray Detector Doesn't Require Heavy Metals
• PCB Design007 Top Ten Editor's Picks
• Career Opportunities section
• I-007e Educational Resource Center
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