Boards fail for various reasons, and because I’ve been part of the PCB industry for a long time, I’ve seen most of the reasons for failure. My experience also tells me that while some issues are out of left field and unforeseeable, most board failures are the result of common issues with design. As part of my ongoing crusade to help designers design for the reality of manufacturing, here are five common causes for board failure and how to avoid them:

1. Ensure You Have a Clean Schematic

   Designers don’t read minds; they read schematics. Design and manufacturing processes run smoothly when engineers make the document as functional as possible. It seems straightforward: Place the required components and connect the wires/traces to the appropriate point on the components. Other factors to consider before a schematic magically becomes a PCB design include physical and environmental design constraints, electrical interaction between signals, heat dissipation, and signal loss through the wires/traces.

   This is why the designer needs as much help from the engineer as possible. If a PCB designer has to interpret the schematic there is potential for trouble down the line. To ensure nothing is lost in translation from schematic to design, adhere to these best practices:

   • Start with a block-level diagram
   • Label all connects with comprehensible net names and avoid using auto-generated names
   • Lay out the schematic in a manner that clarifies locations
   • Label the schematic so that the next person working with it will easily understand it
   • Keep communication lines open, so designers can ask for clarification from the engineer if they are uncertain how to proceed. A quick back-and-forth, double-checking their understanding, could prevent a board failure
   • Use the design rule check (DRC) tool and do not allow any design with schematic errors or warnings to be built

2. Design for Drilling Efficiency and Accuracy

   To improve the efficiency of drilling during manufacturing and help cut down on errors that can result in damaged or unusable boards, designers can take the following steps:

   • Group components with like hole sizes together. This requires less drill movement and speeds up the drilling process.
   • Reduce the variety of through-hole sizes from the PCB design by paying close attention to allowances. This will help reduce the number of tool changes required during manufacturing. Boards cost less, get built faster, and have less opportunity for error.
   • There are pluses and minuses if you choose the smallest possible hole sizes during design. Smaller hole sizes can reduce the amount of material that needs to be drilled and removed from the board. However, most small-diameter bits have similar parameters regarding revolutions per minute (RPM), feed rate, chip load, and retract rate, so the improved drilling efficiency is usually pretty small. Smaller bits are more prone to deflection by the glass fibers in the laminate material, can create aspect ratio issues during plating when the board thickness to drill diameter ratio is too high, and may impact overall hole quality.
   • Make sure there is enough space between holes to ensure the structural integrity of the board and avoid drill bit deflection during manufacturing.
   • Pay attention to the allowances for various through-hole requirements. If multiple allowance ranges overlap, select a through-hole size that accommodates as many allowances as possible.

3. Manage Solder to Reduce Heat Sink Failures

   Heat-sink failures are common and can be difficult to detect, especially when the failure rates are low. However, even if the volume of failures is low, those costs quickly run into thousands of dollars. Common issues include:

   • Uncontrollable, unpredictable solder
   • Solder wicking through vias
   • Solder movement under large pads

   To avoid these problems, first, prevent solder from wicking through vias and ending up on the wrong layers of a PCB. Second, prevent solder from moving past its area of application. To achieve this:

   • Apply solder mask over the landing pad and open circular “islands” for paste application. If the solder will not behave in a large area, break that area into an array of smaller areas. Since solder mask restricts the paste to its area of application, this reduces the amount of solder connecting the chip to the board, increasing the consistency. Circular solder paste apertures release the solder more reliably than those with sharp corners, which helps prevent loose solder balls.
   • Surround the “islands” with small (~12 mil or smaller) vias that are tented and covered with solder mask. Removing the vias from the immediate area being soldered and tenting them prevents any stray solder from wicking down to the other side of the board while still providing good thermal transfer to the pads underneath. Add these vias as close as possible to the islands. The solder mask tenting will block any solder that wicks onto an exposed via due to manufacturing tolerances.

   We recommend designers include this as part of their package definition, uniformly applying it to all similar parts in the design.

4. Respect Your Power Supply

   It’s important to deliver the required power to each component on a PCB, but it can be a complex design challenge. Failure to manage power properly can cause overheating, short circuits, signal distortion, component malfunction, or even complete board failure.

   Designers must manage converting AC to DC while also delivering the correct voltage and current to each component. A well-designed PCB results when the designer takes power supply seriously, paying close attention to the effects that power delivery can have on surrounding components, such as through heat management or signal interference.

   • Design to maintain power quality and integrity, so power is effectively transferred from the power supply to every component, circuit, and device as expected. Your design needs to ensure that all components are supplied with the appropriate power level to achieve target performance of the entire circuit.
   • If your board has three or more layers, keep the power and ground planes on one of the internal layers. This will add structure to the board, and it gives easy access to both power and ground from other layers while keeping your PCB design clean.
   • Separate your ground and power planes to reduce electromagnetic interference while distributing power. Not only will this reduce strange signal patterns, but it can help prevent unexpected voltage drops.

5. Don’t Let Parts Issues Impact Manufacturability

   Issues with how parts fit on a board are among the most frequent causes of delay and cost overruns. PCBs with ill-fitting parts have issues with performance and durability, reducing the overall quality of the board. Here are some methods to avoid problems with parts fit:

   • Pay attention to the hole sizes for component pins. Check component physical dimensions, take dimension tolerances into consideration, and account for variation that can affect fit. Pins can be the wrong size or have the wrong spacing, and components can be larger than their footprint or land pattern indicates. Watch part sizes and pay attention to the minimum, nominal, and maximum material conditions for the original part.
   • Watch for holes in the footprint differing from pin size. If hole sizes are too tight, pins may not fit through the holes, or if they do go into the holes, they may not solder well. When designing the land pattern, you can find the pin size and tolerance range for components in the product datasheet. Use that information to plan the proper hole size.
   • Datasheets can disagree with CAD software. When the datasheet and the library part don't match up, resolve the delta before submitting the design. Check every part in the library against the data sheet before using it for the first time.
   • Pay attention to pinouts when using alternate vendor parts. Even if pin size and through-hole size are a confirmed match and solder joints appear sound, a part can still not work as expected. Similar parts with the same footprint might look like they should act identically, but they won't always have the same pinout. Each transistor has a gate, drain, and source, but manufacturers can differ in what goes where. Be aware of this as you select parts for your design.
   • Be aware of mechanical fit. It's not just the footprint and through-holes that are important. The physical size of a component can keep parts from fitting into designated spaces. MMC body size should be the rule, so pay attention to the tolerance range.

Read Matt’s book, The Printed Circuit Designer’s Guide to… Designing for Reality, or listen to his podcast here.

This column originally appeared in the August 2025 issue of Design007 Magazine.