Do I need a custom PCB design for my product?

by Patricio Cohen, Electronic Design Engineer

Almost always yes, but in the end it will depend on your application

Should I design a custom PCB or should I use a bunch of cheap development boards instead? This a very common question.

Today there are lots of cheap development boards available in the market for everyone that has interest in electronics. People can learn electronics at home without the need for expensive equipment. Students can easily build basic project ideas and test specific concepts at the university. Also, entrepreneurs can rapidly test their business ideas before building the definitive product. Examples of these type of development boards are the Arduino family, Raspberry Pi, Beagleboard and so forth.

Given their low cost, it’s natural for some people to ask why shouldn’t they use them for their commercial product. The answer to this questions is – it depends.

When designing a custom product idea, the odds that you will find an off-the-shelf development board that will exactly fit your needs are almost zero. Given this restriction, it will be necessary to use several boards and/or breadboards with connections between them. The nickname “Frankenstein System” is a very good one due to the fact that the whole system consists of several parts (boards) put together.

Frankenstein systems are very good for learning purposes, for testing very specific concepts and/or for having lots of fun as a hobbyist. However, they could be unreliable and impractical for industrial and commercial products as we will explain below.

Let’s review some important requirements that Frankenstein systems don’t have.

Corporate image

If you want to market the product as your brand you must have some kind of corporate image. Most of the products must have an enclosure not only to protect the circuitry from the outside environment but also to give it an identity and facilitate user experience. It’s true that in some cases circuit boards alone are the only product since there is no need for an enclosure. However, some kind of corporate image must be present so customers can identify your product from competitors. Selling your product as a bunch of boards with wires in between is not something that will help you to position your brand in the market.

Enclosure requirements

For most products, the electronics need to be inside an enclosure. Therefore, you can’t leave out of the equation characteristics such as their size, weight, and shape. With custom boards, you have freedom for the shape. You can even design one that exactly matches the enclosure with the aid of 3D modeling.

Since off-the-shelf boards have lots of IO pins available, they are generally big, therefore making the product bulkier. This could be something highly undesirable for certain types of products.

Implementation and Maintenance

Having lots of boards connected together not only is error-prone but also time-consuming for your technical team. This is true not only during the setup and production stages but for its maintenance as well. If the product consists of several boards and/or breadboards wired together, the probability of failure is greater as the number of boards increases. In fact, temperature and vibration produce problems in wired connections which can produce detrimental effects in industrial applications.  If the system is error prone you will need to provide technical assistance more frequently. Also, maintenance tasks will be more daunting and resource consuming as the Frankenstein is bigger.

Designing a custom PCB for your application is without any doubt the best choice. You will have the smallest possible system and also fewer connections to be made (this is also true for multi PCB projects). Also, the incorporation of hardware checking features can provide additional peace of mind. In the end, maintenance will be a lot easier, less costly and a lot less frequent.

Intellectual property

Cheap off-the-shelf developments boards have tons of information available at your disposal. This information is available through forums and other websites with huge numbers of users and visitors. In these places, you can ask almost anything about hardware and software. Some of these boards have application software inside an SD Card that can be easily copied.

Last but not least, lots of these boards are open source. And this obliges you to make your project open source too.

Manufacturing cost

Again as pointed above, these boards are big because they need to expose all IC pins. They do this by providing big headers that are designed to quickly wire connections to other boards or breadboards. Is not uncommon that some components (IC’s and connectors) are not required in your application. This is obviously a waste of resources in board area and components, which in big quantities could be a lot of money.

On the contrary, custom boards have exactly the resources they will need to use. No money will be wasted.

Reliability

Development boards as their name says are for “developing” or testing a concept. Also, their target market isn’t system manufacturers but hobbyists, students, and entrepreneurs. That is why mechanical and electrical reliability over time is not something they are concerned about. Their headers, for instance, are not appropriate for long-term connections. Sooner or later connections in moving boards will get loose and cause problems with other boards that are parts of the Frankenstein.

If you are intending to use your product in an industrial environment, there are other things you must be aware of. Especially important are the detrimental effects due to undesired mechanical and electrical events that are common in these type of environments.

Some of the very basic questions you must ask yourself about off-the-shelf development boards you intend to use are:

• Can they operate under an industrial temperature range?
• Is the board immune to external electromagnetic noise?
• What happens when input power surges occur?
• Are the input lines protected against over voltages?
• Are the types of communication interfaces available appropriate?

On Frankenstein systems, any of these scenarios most probably will make the system not to perform as expected and could be permanently damaged. This is because they are designed to be very cheap and not for this type of applications.

Analog performance

It’s true that these boards have ADCs and DACs for mixed signal applications but their performance is usually very limited. They are only useful for DC/low frequency and relatively big signals. This is because reliable analog to digital conversion demands multilayer boards and very careful design techniques to minimize contamination by external noise. If you need to convert very small signals, you are probably going to have lots of noise related problems.

In cases where the whole solution consists of a bunch of boards through wires, the result is far worse. Custom PCBs on the other hand, if they were designed for analog applications that need to measure very small signals, reliability and analog performance will be guaranteed by design. Also for all our designs, careful attention to PCB layout and circuit design are considered from the very beginning. This is to avoid signal integrity and EMC problems.

It is important to take into account, that depending on the signal you want to convert to the digital domain, you will have to consider designing a front-end or signal conditioning block. On a custom PCB, this will be very close to the data converter circuit for best results. On the contrary, in Frankenstein systems, this is not always possible and impairment of analog performance can happen.

Real-time performance

If you need to acquire signals starting at the hundreds of kilohertz or megahertz range and you are planning to use this type of boards you are absolutely in a bad direction. Even if they had the appropriate hardware for doing analog to digital conversion at those frequencies, the lack of digital signal processing power will render these types of boards useless for such applications. Here a custom PCB is the only way.

Low power consumption

This is a key factor for lots of embedded systems that must consume very little power. Wireless sensor networks are a very good example. Engineers in these cases need to use several techniques to extend battery life. Careful use of low power modes, underclocking processors and turning devices off and on are always necessary. Also, the hardware must be carefully designed to avoid current leaks (here micro amps are important!). In other words, you need full control of the hardware and software resources. Cheap off-the-shelf development boards are not very power efficient, therefore your available battery power could be depleted in a very short time.

Conclusion

If the observations addressed above doesn’t affect your product, then you should use a Frankenstein System based on cheap development boards because they are the best option in terms of cost and time. It makes sense to me that maybe only low-end and very small scale products could benefit from this type of systems. However, if you are serious about developing and marketing products, you need to consider all the points mentioned here. In the end, this means that best way is to go is to design a custom PCB for your project.