Across all industries, component shortages are forcing design engineers to seek alternative parts and materials, or entirely redesign their projects.With analysts predicting the shortages to last potentially through 2018, the market is scrambling to find ways to keep projects on-time and on-budget. One common practice currently compounding the challenge of limited supply is a refusal to accept part substitutions.


When designing a new board or revising an existing project, engineers tend use familiar parts. This reduces risk of the board not working and makes it easier to put together the necessary files including a Bill of Material (BOM).  To ensure their designs are assembled exactly as specified, they sometimes will include a note that says “No Part Subs.” This means that if the designated part is no longer available, out of stock or obsolete, substitutions are not allowed. However, when inventory is limited, there are many reasons why “No Part Subs” is a bad idea.


First, it reduces the chances of getting an accurate quote. When it is only possible to get pricing on half of the components listed on a Bill of Materials, for example, the resulting project quote will be significantly lower than the actual project cost.


Second, when part substitutions are not allowed, it takes more time to locate and purchase the parts, if they are available at all. Frequently, sourcing BOMs with No Part Subs can take days to weeks.  Of course, without all the parts, the order can’t be completed unless the engineer agrees to have the boards assembled without all the components. This is known in the industry as “Do Not Install” the parts in question.


Third, the practice of not considering part substitutions increases the amount of back and forth communication between the design engineer and whomever is buying the parts.  Consider that a typically BOM includes 30 to 80-line items and, upon an initial search, the quoting or sourcing teams finds approximately two-thirds of the parts. That leaves many parts in question, which must be resolved one at a time.


It is highly recommended to be open to substituting any part that matches fit, form and functionality. If that is not possible, at the very least, consider allowing part substitutions for passives only. This provides confidence that the main components are purchased as designated but avoids all the other issues associated with locating passives. By allowing possible alternates, you can lessen the impact of the part shortage and get completed projects when you need them – even the next day.