6 Key Considerations When Starting a New PCB Design

How often have you said to yourself, "I wish I would have known that earlier!" It's a fact that hundreds of decisions need to be made when starting a PCB design. The real struggle is which decisions need to be made first. A missed (or wrong) choice is similar to casting concrete. Once it's poured and cured, there isn't much that can be changed without a jackhammer. Many PCB designs have often been delayed or scrapped because of an overlooked decision.

This webinar will cover 6 key considerations that need to be made before starting any new PCB design:

• 1. Fabrication
  

• 2. Electrical
  

• 3. Mechanical
  

• 4. Regulatory
  

• 5. Procurement
  

• 6. DFM / DFT (Design for Manufacturing; Design for Test)
  

A cautionary note was brought to our attention regarding the bypass capacitors. "Usually generosity with bypass caps is a great thing, but beware LDOs as most go unstable if you go beyond the specified capacitance in the datasheet. There are a few out there that are stable at any capacitance." One example comes from Analog Devices: https://www.analog.com/media/en/news-marketing-collateral/solutions-bulletins-brochures/257253984LDO.Family.bulletin.pdf

One cannot go by a universal 15% rule of thumb because speed depends on the Dk.

Even if the Dk is the same for all dielectrics involved, a single rule of thumb cannot be created because one must account for the ratio of air and solder mask material creating an "Effective Dk."

You can see below the effect of the dielectric's Dk getting closer to air:

       For a Dk = 4.6, the stripline would be 182 ps/in
       Microstrip would be 144 ps/in, a speed increase of 20.88%
       Embedded microstrip would be 168 ps/in, a speed increase of 7.68%

       For a Dk = 3.3, the stripline would be 154ps/in
       Microstrip would be 127 ps/in, a speed increase of 30.22%
       Embedded microstrip would be 142ps/in, a speed increase of 21.98%

Also, the microstrip geometry will need to be adjusted for impedance, which depends on Dk.

The Saturn Electronics website provides equation-based calculators. One can get good approximations, which is far better than a universal rule of thumb.

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10 things that may surprise you about engineers in the PCB process

At Nine Dot Connects, we address the "pain points" in the PCB design flow, from an EDA tool's functional capabilities to the PCB process itself. We can do this because all of us at Nine Dot Connects has walked a mile or two in your shoes.

We have learned (the hard way through experience) that engineering and business mix like oil and water. Much like many things in life, the PCB process that we logically believe should happen is not the PCB process in place. By understanding what makes us engineers tick, we can address the PCB process from a different, positive, and productive angle.

This webinar will focus on several observations we have made here at Nine Dot Connects as we have interfaced with numerous engineers and managers. These observations are so evident that quite frankly, they are not obvious. Join us for a webinar meant to cordially explain those engineering idiosyncrasies that you and your colleagues were never comfortable discussing with management.

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A Short History of the Short History of Printed Circuit Boards

Departing from our traditional in-depth technical topics, we want to cover a short history of Printed Circuit Boards (PCB). We want you to relax and enjoy the information.

In an odd sense, PCBs and their manufacturing advancements have been a response to history itself - The product innovations of the roaring 1920s, the foundation for communication equipment during the 2nd World War and beyond, the backbone for the innovations brought on by the inventions of the transistor and the IC, and the "right stuff" for the electronics needed for landing a man on the moon. And, of course, the "glue" propelled us into the internet age.

Please join us for a bit of history on the PCB. And remember, those who fail to learn from history are destined to repeat it (or in our industry, respin it!)

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To Route or Auto Route

We put this webinar together to address the complex issue of autorouting. It is a "high-level" presentation to look at the history and algorithms commonly used. As you will see, the effort is not simple. Routing a particular line is one thing; however, planning and prioritizing the routes are challenging. It is much like the old "chicken and egg" conundrum. The router must know the congestion points to prioritize routing; however, it does not know them until it starts to route.

We must also understand that the placement of components and real estate also plays a role in the ease or difficulty of autorouting. These are factors that are controlled outside of the autorouter.

The biggest effort in autorouting is constraining it. There need to rule in place to ensure that the routes are viable. There is a delicate balance. The more we constrain it, the more difficult it gets for the autorouter to complete the route.

More importantly, we must consider the time it takes to the autoroute. It is rare to get the routing correct on the first attempt. This is reviewing the result, modifying the rules or constraints, tweaking the strategy's order, and rerunning it. When the autorouter is done, the work must be reviewed. There will be odd routing formations that are "legal" within the constraints but would be considered poor routing practices if routed manually. Whether one wants to pour over the layout visually and correct issues or hand route each line and review the work as they progress.

In the end, we must decide whether or not to use an autorouter. This question completely depends on the board real estate, the number of components and pins, the clearances allowed, the strategies available, and the number of layers within the board. Though autorouters are used, most boards are still routed by hand. The human mind is still the better "autorouter."

Several EDA companies like Altium have moved away from the all-encompassing autorouter. An all-purpose router becomes a no-purpose router. There are too many scenarios and factors to make this viable. They recently introduced local routers that let the autorouter focus on a specific location. Once the router has completed the task in the space provided, the user can immediately review and clean up before moving.

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