How do you choose electronic components?

You need to be able to source electronic components for your new product that reach your cost, quality, and reliability expectations. In fact, the success of your product is riding on the components that it’s made up of being perfect for the job. It’s not as simple as just going online and choosing something that works, either. In order to find perfect components, we follow this process…

What follows is a summary of the electronic component selection steps, but I discussed it in far more detail on our group’s podcast here.

The electronic component selection process is more complex than many people think. Proper electronic component selection is not actually as simple as going to Radio Shack, buying a part, and just using it as long as it works. Today’s manufacturers need to make sure that their components to be used in mass production meet certain criteria and there are many elements to consider during the sourcing process. We’ve broken the process down into 18 steps…

1. Define your Requirements
To define your requirements you’ll consider what your product does, its users, the environment it will be in, and how this particular component needs to function in order to help it achieve its goals among others. Each part’s cost, specifications, etc, must be noted now, too.

2. Select the Key Components
Key components are those that the product relies upon to function correctly. For electronics, it might be a display, type of chip, enclosure, etc. Without these, you are in trouble so they must be noted and considered with care.

3. Analyze the Operating Environment/s
Note your product’s intended operating environments. Components that can handle the environment without failing are crucial, otherwise, the product will be unreliable.

4. Identify Critical Parameters per component
Your requirements will demand that components that work in a specific range must be sourced, therefore you need to work on the range of parameters you need for each part. This might be voltage, tolerances, etc. If you select parts without the right parameters you may find that they fail if the environment alters slightly, such as a power surge, or those that are too highly rated just cost you too much.

5. Source the Components
Sourcing components directly from component manufacturers is usually the best option in terms of cost and reliability of supply. You should always obtain the datasheets and check the specifications against your requirements.

6. Consider the Supply Chain
It will reduce risks of disruption if you choose to source from well-established and professional manufacturers. At the same time, find a second-source supplier, especially for key components, so they can step in and supply you if there is ever a problem with your main pick.

7. Check for Obsolescence
Design engineers should be wary of each part’s lifecycle and confirm with the manufacturer that they plan to produce it for the long term. This will reduce the risks of you incorporating a part into your new product that is then suddenly unavailable.

8. Analyze costs
Purchasing components at the right cost impacts the sale price of the product. If you buy in large quantities prices will be far lower, so it’s better to find a supplier who can supply your required quantity at a reasonable price.

9. Selecting Components at the right level of Reliability and Quality
To guarantee better reliability you should try to select parts that have a margin of reliability, for example, they can handle temperatures outside of the usual operating environment of the product. To do this, you need to perform reliability testing on samples of the parts.

10. Purchase Second-Source Components
If you have found second-source suppliers for your critical components at least, be sure to purchase some and then if there is an emergency you will already have a supplier who can step in and won’t have to do the sourcing process from scratch causing delays.

11. Component Database
Implement a component database and keep it updated with new versions of datasheets, version numbers, etc. Be sure to remove obsolete information so your team only sees up-to-date information about the components.

12. Design for Excellence, especially DFM
Use DfX to design your product with design goals in mind that will reduce risks later on, for example, Design for Manufacturing, or DFM , is a popular principle to embrace because it emphasizes designing the product to be easier and more straightforward to manufacture and at a lower cost.

13. Compliance and Standards
Check each component’s datasheet to confirm that it complies with the safety standards and regulations of wherever you intend to sell it. If you unwittingly miss a compliance requirement it’s very unlikely you can sell the product which will be a disaster if they’re all waiting on the docks in a container.

14. Simulating and Prototyping the Product
Now you can make tangible samples or prototypes. You will use the components to make rough prototypes at first and then, as you iterate the prototypes, they will get closer and closer to production standard. This helps you to qualify and validate the functions, performance, looks, etc, of the product.

15. Documentation and Record-Keeping
The many changes that design engineers make to the product during the development process need to be documented so progress can be tracked and team members know when changes were made. Fixes to problems may be collected in a lessons-learnt database, along with dates, who made a change or fix, etc.

16. Design Reviews
Not long before production starts you will have done a lot of testing on components and prototypes and will be close to satisfied that it looks and works correctly, reaching your goals and expectations. But, before signing off, a design review meeting should be called where all engineers and management examine each part of the product being in mind if it reaches its requirements. The purpose is to validate and verify that the product reaches its requirements for performance, reliability, quality, etc, and functions as expected.

17. Lock the Bill of Materials (BOM)
Before manufacturing the BOM is locked which means that there are no more changes to parts used or designs. Component suppliers are contacted to confirm costs and availability and place orders. Everyone works together to make sure that all of the parts will arrive on time for production to start on a specific date. Then attention turns to setting up the manufacturing assembly line/s, writing SOPs, hiring staff, etc.

18. Pilot Run
Before starting mass production it’s the last chance to check that the components you have selected can be used to manufacture the products at scale. For this, use the components that you have, by now, tested and validated in a short pilot run using the same line, staff, equipment, processes, etc, as will be used in mass production. If there are any production issues, packaging problems, etc, you will encounter them now and can fix them before things go any further and you have produced thousands of units of your product.

Get help

Agilian has a supply chain management team that can assist you in sourcing the ideal components for your needs. Here’s how we manage supply chains for you.
If you have any questions about bringing your new product to market, please don’t hesitate to get in touch with us…we’re happy to offer some friendly advice and let you know if and how can help you.

Speak with the Agilian team

Overview

Surprisingly, many engineers do not pay enough attention to the task of selecting the right electronic component during the initial phase of their embedded product design.

Selecting the right electronic component is one of the most critical & challenging aspects of product design. In this article, I do not aim to explain how to select different electronic components like resistor, capacitor, transistor, digital IC, microcontrollers, relay, connector, display, etc. as there is no one answer to this challenge. The correct answer is, you should know clearly what is your requirements w.r.t a particular electronic component.

There are so many ways to solve the same problem, it will depend on various things like, if you need a compact design, easy to manufacture design, most affordable, most power efficient, least number of electronic components, most reliable, etc.. So, at the end it’s a trade-off, where, you are trying to decide which electronic component matches most of your requirements.

Every electronic component is different and needs specific attention, but, general rules of the game remains the same.

Which all parameters to consider?

To start with, I recommend making a list of electronic components and their critical parameters which needs to be checked. There are a number of parameters which I always consider while choosing the right electronic component.

Hope this will help you next time when you are working on a project where you need new components to be selected.

But before that one important point about electronic components from previous designs.

Electronic component from a previous proven design

The easiest bet would be to use the part you have already used in your previous proven design, this helps reduce the risk of design issues, delays, also no additional part in inventory to manage.

But, this approach has one drawback. If you stick on to an older proven electronic component, you may miss the advantage of a new part, which may bring in benefits like more compact, more integration, more power efficient, better protection, better longevity. When starting a new design, it also brings an opportunity to try newer parts available (maybe you can have a fallback option on board if you have doubts about the new part’s performance).

Selecting the New Parts

Now, let us assume we have to select a part which we did not use before, so how should we approach this challenge. As mentioned before I would list all the parameters which need to be considered and then go refining/filtering from the available part database. Best would be to look for parts available with online distributors like DigiKey, Mouser, RS Components, Farnell, Element14, etc.

Let me discuss some of the parameters one by one, this is based on my personal experience working with many companies on various projects:

1. Manufacturers

Select manufacturer wisely. Always consider a manufacturer who has good product documentation like an informative datasheet, application notes, reference designs, evaluation board support, support channel. For complex devices, you may want to get in touch the manufacturer over email to test their support. If local Field Application Engineer support is available in your country, would be really helpful. Trusting manufacturers who do not have good product documentation and support is tricky.

Application Notes

Application notes from the manufacturer help a lot in understanding the application circuit and many times tested electronic components make/rating is also provided, which reduces the risk greatly. Evaluation board can also be used for pre-qualification.

Some manufacturers also provide a lot of other resources like industry-specific reference design, software tools to help designer evaluate the performance of the electronic component as per your own configurations before even designing anything. This heavily reduces the development time and chances of failure.

Technical Support / Design Review Support

Electroninc component manufacturer’s support is critical.

In case you are stuck, you can ask their engineer’s help. Many manufacturers also provide design review facility which greatly helps when you are designing for the 1st time a circuit with their parts. You can send them your schematics with their part used and they can help you review and tell you if everything is OK or if they have any recommendations.

Many companies maintain a list of the preferred list of manufactures which gets 1st preference.

2. Application Circuit Complexity

New parts need application understanding and many times the application circuit’s complexity drives the part selection. If say part A has complex application circuit w.r.t part B, provided all requirements are met by both, the obvious choice would be to go with part B. But, sometimes that comes with a cost, for example, easy application circuit but at a little extra cost, here comes the trade-off.

Some similar parts might have ESD protection inbuilt, so might cost a little more. Please consider carefully what benefits you are getting, like compact size, easy design vs. implication like dependency on one manufacturer, higher lead times, impact on overall PCB real estate, production testing/repair time, etc.

3. Electrical Parameters [voltage, current, power, accuracy, response time, speed, resolution, etc.]

This is the core of the requirement, Eg: for a resistor, you need to see it’s resistance value, tolerance, temperature coefficient, wattage, etc.

Another example is, consider a DC-DC Converter IC, some of the electrical parameters would be input voltage range, output voltage accuracy, inbuilt protections available like over current, over voltage, under voltage cutoff, thermal shutdown, light load efficiency, power rating, thermal management, etc.

Make sure you make a list so that you do not miss a critical parameter.

4. Mechanical Parameters [dimension, package, weight, etc.]

Mechanical dimension plays an important role in part selection. It starts with, what kind of size constraints you have? Are you OK with a little bigger size or you need to select a package which is as compact as possible? With the smaller package, also comes the complexity of assembling, testing, repairing. Example: if you are select an SMD resistor, it would very hard to manually solder a 0402 package vs. 0603 or 0805.

Another example is the lead-less (BGA / LLP) packages. It will be complex from PCB design / manual soldering point of view, so decide carefully what makes the best sense for your overall requirement. Do you want to go automated PCB assembling route or stick to packages which could be soldered manually?

In general, we should keep the overall weight of the product low as it directly impacts your shipping cost. In some cases, weight might be a bigger constraint like for a wearable product or anything which goes on, for example, a drone.

5. Consideration w.r.t Manufacturing / Testing

Whatever part you select should not create an issue when you manufacture them in bulk or while testing, so always consider manufacturing & testing process in mind while selecting a part. Visualize beforehand, how that part is going to be placed on board and then tested.

6. Environmental Parameters : Temperature / Humidity / Pressure / Vibration

Environmental parameters are also very important, should be known beforehand and be considered carefully. You should know the range of temperate your product will see, then take the worst case analysis and do the selection, likewise for other parameters.

Check properly operating/storage temperature, humidity, pressure, vibration range and its effect on the part performance. Missing this consideration may lead to field surprises like field failures or bad performance.

8. Long term availability / End of life (EOL)

Whenever possible, select an electronic component which has a pin-compatible alternative. But, that doesn’t mean you compromise on critical specifications.

Long-term availability is a big topic whenever you are selecting an electronic component, as you don’t want to design a circuit with a part which is going to be NRND(not recommended for new design) soon.

So, make sure your electronic components especially ICs, MCUs, Connectors, Display, etc. which are selected, have min. 5 to 7 years (or as per your requirement) availability. If you have any confusion or information about availability is not available, you can check with the manufacturer. You can also use CIIVA from Altium to know the life cycle status of an electronic component.

I wrote an article on how to find equivalent electronic components, please read it.

9. Lead time

Lead time plays an important role. This can totally screw up your development roadmap if you missed considering it beforehand. Sometimes sample lead times are short but when you try to buy a bigger quantity, lead times are higher, so be careful.

If lead times are high and you don’t have a choice of another part, you may need to keep some extra stock. This has an effect on your overall cost of the product.

10. Cost

Everyone wants to have the best electronic component at the most affordable cost. Don’t compromise on quality if you are getting at a lower cost. Sometimes device cost more due to better performance, more power efficient, smaller package, more integration (like optical isolation, ESD protection inbuilt in RS485 transceivers, etc.), better reliability. So, consider overall value-add rather than just the cost of an electronic component.

Don’t just buy lowest cost electronic component, see the overall cost impact on BOM, production time, repair time, etc. If you consider this way you can take a better decision.

11. From where to Buy

This is critical.

As mentioned earlier, I always recommend buying electronic components from trusted sources like directly from the manufacturer if possible, authorized distributors, etc.. I do not advice to buy from a shop (online or physical) where genuinity of electronic component is not assured.

One may find it attractive to buy from a local vendor as it is available off-the-shelf and many times at lesser cost, but, in case there are any issues with the quality of electronic component, you may end up paying the price by loosing on precious time wasted on debugging.

I have experienced this several times in the early days of my career so I always keep this in mind.

12. Fall Back Solution / Assembly options

It is always a good idea to keep some fallback /assembly option (if required) for the new circuit you are designing so that in case one circuit option doesn’t work, you will have another possibility. This many times saves manual patchwork, even redesign.

In some of my designs, I have used assembly options to make two different types of DC-DC converter chip compatible for power supply section as I was unsure about the long-term availability, lead times of the part. This helped me with long-term availability and more flexibility as now I had two options.

Assembly options are also useful when you want an option in your board to bypass a section in case it is not required. You may put an optional zero ohm resistor.

13. Design Reviews

Follow 3 level review process: 1st – always do a detailed self-review. A 2nd review should be done by someone else than you in your organization. If possible (recommended) get it reviewed by an external experienced engineer or consultant if you don’t have confidence. By doing reviews this way, your design, the part selection is getting questioned by multiple people and chances of errors, effort/time loss in re-spinning the design would greatly reduce (if you have setup a proper guidelines, process for the review).

14. Prototype before you plan production

For complex part selection, it is always advisable to test application circuit for that particular electronic component either using the evaluation boards or by making a small board, before including in the full design.

Once the part is tested and performance is evaluated, it can be included in the full product design. Many companies do the full design itself but then they are aware that they are taking the risk and if some problem comes they need to redesign and get it manufactured again. So, take an informed decision on what is best for you.

Hope these 14 point considerations will help you in your next design.

If you like the article, please share it with others. Any suggestion or comments, let me know here. Read my other articles on embedded system design.

Happy Learning to you!

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