Connect the Dots: Designing for Reality—Routing, Final Fab, and QC
Target Condition: ‘Boomer to Zoomer: Do You Copy?’
Elementary, Mr. Watson From Classroom to Career—Bridging the Gap in PCB Design Talent
Mark Thompson's Biggest Problems With PCB Designs
July 6, 2023 | Mark Thompson, Out of the Box ManufacturingEstimated reading time: 1 minute
What are the top problems I see with PCB design? From where I sit now on the assembly side, one of my biggest concerns related to PCB design is the lack of uniform part markings on the Gerber or ODB++ data, specifically the way customers reference diodes. We would prefer either an “A” depicting the anode side or a “C” or “K” for the cathode side. Many customers simply use either a line or a dot, which requires us to contact them to clarify which side is the cathode and which side is the anode.
If a line is used to denote the cathode side, many times the silkscreen clip using the mask clearance by the fabricator wipes out most of the line, making it difficult or impossible to determine the location of the cathode side. Using a dot doesn’t really help; does a dot depict an anode or cathode? Besides, dots are typically used to denote Pin 1 designators. Please use an “A” for the anode side and a “C” or “K” for the cathode side.
Controlling Controlled Impedances
Another area that concerns me is controlled impedances. Don’t make assumptions about controlled impedances. Your goal as a PCB designer is to simulate impedance to within 10% of your goal. The fabricator should be able to take it the rest of the way since the fabricator knows its press parameters, press values, and effective Dk. Trust your chosen fabricator and use the numbers they provide you.
If you simply go online and check material PDFs for the purpose of establishing impedances yourself be aware that many of the generic spec sheets are for very thick dielectrics (.014" core and sometimes even .028" core) the Dk associated with the thicker dielectrics are higher which, if used for trace widths .005" and below will create a mismatch and the fabricator will come back with a line size that your space may not support.
Also, consider the speed. If the literature is showing 4.5 Dk at 1 Mhz, and you know this product will be running at higher speeds, such as 5,10 or even 20 Ghz, understand the Dk will be driven way down. You may be looking at something closer to 3.8 Dk at 5 Ghz and the mismatch will affect the impedance.
Mark Thompson is an engineering manager with Out of the Box Manufacturing and a longtime CAM expert.
This article appeared in the June 2023 issue of Design007 Magazine.
Share on:
Suggested Items
Strategic Materials Conference 2025 to Highlight the New Era of Materials Innovation
02/12/2025 | SEMIWith advanced materials as a critical enabler of semiconductor growth applications, the Strategic Materials Conference (SMC) 2025 will gather top executives and technology leaders from the semiconductor manufacturing industry for exclusive insights into the latest advancements in materials innovation.
American Made Advocacy: New Congress, New Opportunities
02/04/2025 | Shane Whiteside -- Column: American Made AdvocacyLast month, I spent two days in Washington, D.C., discussing the need for policies that level the playing field for our technology providers and the tens of thousands of workers they employ. As you might expect, the 2024 elections have reordered Washington, but doors remain open for the manufacturing community, and I am optimistic that actions to reshore and rebuild are possible.
Effects of Advanced Packaging and Stackup Design
12/26/2024 | I-Connect007 Editorial TeamKris Moyer teaches several PCB design classes for IPC and Sacramento State, including advanced PCB design. His advanced design classes take on some really interesting topics, including the impact of a designer’s choice of advanced packaging upon the design of the layer stackup. Kris shares his thoughts on the relationship between packaging and stackup, what PCB designers need to know, and why he believes, “The rules we used to live by are no longer valid.”
VDL to Produce Crucial Components for New Medical Isotope Reactor
12/18/2024 | VDL GroepVDL Groep is working to further broaden and strengthen its hightech activities. The industrial family business with its headquarters in Brainport Eindhoven is taking its first, substantial steps into the nuclear sector, a key growth market. Operating company VDL KTI in Mol, Belgium, will produce and supply crucial components for the new PALLAS reactor in Petten.
VDL to Produce Crucial Components for New Medical Isotope Reactor
12/16/2024 | VDL GroepVDL Groep is working to further broaden and strengthen its hightech activities. The industrial family business with its headquarters in Brainport Eindhoven is taking its first, substantial steps into the nuclear sector, a key growth market.