Best Part Swap Opportunities to Reduce PCB Cost

When designing for PCB prototyping, the cost of individual parts does not always play a big role. If you're designing one-offs or hobby projects, you'll probably only look at parts prices when your assembly house sends you an invoice.

But if you're eventually going to produce at scale, the cost of the prototype is small compared to the BOM cost over the product’s lifetime. When it's time to make that transition to volume manufacturing, the BOM cost becomes a big factor and every component becomes a candidate for cost reduction.

To help designers who need to identify BOM cost reduction opportunities, there are some simple part swap choices you can make. The cost savings per part might be small, but small savings per part always adds up to very large numbers. Here are some of the basic things to look for when deciding on part swaps to reduce PCB costs.

Reduce PCB Cost in Your BOM

There is a fine line you need to tow when identifying part cost savings in your BOM. You need to make sure that you preserve all the important functions, and you don't want to create quality or reliability problems when swapping parts. But during prototyping, we sometimes jump right to the parts that are available in a library rather than scanning each line of the BOM for the lowest cost parts that still meet specs.

Keep this point in mind and make a list of the most important specifications that apply throughout your BOM. Some of the most common blanket specifications for all parts in a build include:

• Operating or storage temperature range

• Compliance to some industry standard, such as automotive standards

• Compliance to some safety or ESD standard, such as an IEC standard

• Limits on moisture sensitivity

• Compliance with RoHS/REACH

• Z-axis profile of the component (needed for mechanical compliance)

After taking some time to determine the most important high level specifications, you can start looking for swap opportunities that will reduce PCB cost.

Connectors

While it's not always possible in every design, connectors offer an opportunity for cost reduction. connectors can be pricey because of their physical size, but there are many alternative connectors that can be procured at volume.

For example, a good way to reduce costs is to use standardized connectors when your product must use a cable. For power, that means using a barrel jack; for data, that usually means something like USB. For many other interfaces, that might mean swapping for a standard pin header or mezzanine connector. Using a single part number for headers is a great way to reduce BOM lines while also potentially gaining a larger volume discount.

Use a common connector option to get volume discounts on components.

SMD Passive Components

Passive components are the most common parts used in PCBs, so of course they are an excellent place to look for opportunities to reduce BOM cost. SMD passive components come in common case sizes that make part swaps incredibly easy. Some of the simplest ways to reduce part costs throughout the BOM include:

• Switch from high to low precision components where acceptable

• Consolidate duplicate parts to a single part number (single BOM line)

• Swap a large case size for a smaller case size to reduce number of BOM lines

• Switch to lower voltage or power ratings where acceptable

All of these approaches are meant to reduce the number of BOM lines and use less expensive parts. By reducing the number of BOM lines, you will reduce assembly cost because pick-and-place machine time cost is determined by the number of unique lines in the BOM. You can get a volume discount on the consolidated part number as this will require a higher quantity per assembly. 

IC and Semiconductor Ratings

Some of the basic safety and compliance ratings for ICs and semiconductors are also areas where part costs can be reduced. Higher temperature ratings, industry classification, isolation ratings, and even moisture sensitivity ratings all bring higher cost. A quick look through the bom will most likely reveal some components that have ratings which are higher than necessary, so this gives a quick opportunity for cost reduction.

The most common semiconductor that creates excess costs due to over-design is MOSFETs. Some MOSFETs come in packages that are quite large and could have excessively high power ratings. These ratings could be much too large for the circuit where they operate, so examining these components creates an opportunity for significant cost reduction. Another component where you see the exact same problem is with diodes: these are often also chosen such that they create over-design and thus excess costs. Swap these for lower-rated components as long as it will not impact reliability.

DPAK packaged MOSFETs tend to be very rugged, but swapping these out creates an opportunity for cost savings.

When you’re ready to prepare your product for volume PCB assembly, make sure your company uses the best PCB design features in OrCAD from Cadence. If you’re ready to take even more control over net logic and board layout, you can graduate to Allegro PCB Designer for a more advanced toolset and additional simulation options for systems analysis. Only Cadence offers a comprehensive set of circuit, IC, and PCB design tools for any application and any level of complexity.

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