In my home laboratory, the garage, I have many bins. One contains small springs, another gear-motors, yet another small bolts… and so on. Despite my girlfriend’s skepticism, these bits are actually very useful for fixing assorted gadgets and household appliances, and they also provide fodder for my weekend tinkering habits. Keeping track of what I have and where it is uses up quite a lot of mental capacity in itself. At work, the sheer volume of components makes it necessary to have good software for managing of this information. Aside from freeing up brain power for other tasks, there are other important benefits. Allow me to demonstrate.
Managing small changes can take Large amounts of time
Oftentimes, component suppliers are kind enough to send you notices that a part is going obsolete once you’ve ordered a few. This can be very handy for preventing the type of panic attack that occurs when your contract manufacturer stops your biggest client's most important production run due to shortages on the eve of your boss’s anniversary party. Given this information, it is necessary to find a replacement for the part and document the change in every BOM in which it’s used. But it doesn’t stop there. Every new component needs to be vetted as part of it’s final assembly before a change is released. To do this in a timely manner, you’ll need to be proactive and organize how your information is managed.
Finding alternate parts
Naturally, a good first step is finding the new part. For most passive components, finding a suitable replacement part is not too difficult. The component must have the same footprint and value, and have good or better specification values. For example, tolerance, power dissipation, voltage rating, frequency response, etc. For active components, or for passives like transformers with multiple pin-outs, close attention must be paid to pin assignment. A comparator that meets all of the performance requirements may still not be pin-compatible, so be sure to double check those pin assignments. The result of using the wrong parts can sound like popcorn, but doesn’t smell nearly as nice. To avoid that scenario, most modern CAD software comes with component libraries to manage this type of information.
Using the wrong can sound like popcorn.
Considering the Bottom Line
The cost of the replacement is another consideration. Often a direct replacement will have a similar cost, so no sweat. Still, strange things happen in the market of supply and demand and costs can change drastically. On these occasions, making the right decision means considering alternatives such as whether or not there is head-room in the design to use a cheaper component with different specifications. If not, and the cost becomes prohibitive or a replacement can’t be procured, you might be looking at board re-work to use an alternate pin-out, or even a re-spin. BOM revision control and rework documentation can quickly become complicated to track in these instances, though good software can help.
If a direct replacement was not available but a similar part was, it is important to consider how the component affects the design, and why the original was selected to begin with. For example, a component can be chosen in order to reduce the number of part-types required in a design. Sometimes such component’s specifications will exceed the requirements of the circuit. When cost is critical, these decisions may also need to be re-evaluated. Good notes that are clearly associated with the schematic will help to figure things out more quickly.
Consider how things are organized.
Where Did I Put That?
Once the selection of the replacement has been finalized, finding where the original part was used becomes the next task du jour, or du-week (as it were) depending on how many designs it was used in. Finding every instance of where a component was used in every product of the company can prevent some very unwelcome surprises. When it comes to things that machines do much, much better than humans, this is an important one.
Using Altium, I have the benefit of using BOM Management tools to solve many of the above problems. Aside from helping immensely by comparing component specifications and availability across suppliers while using real time pricing, there are great tools for figuring out where components are used. These features make it much easier to manage the necessary information for complex PCB assemblies. So make life easier. Be more popular at parties, and more organized at work. Give Altium a try!
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