What Are the Different Stages of Electronic Prototyping?

When prototyping, here at Ignys we typically create an A model, a B model, and – depending on the project’s complexity – a C Model. From here, we’ll move on to unit production models.

It’s worth acknowledging that the A model will be wrong. The A model is the first time you combine all the design efforts. You are integrating different people’s pieces of IP onto the board, and each person’s IP will typically come with different data sheets.

The data sheets could be wrong or differ from those of others. For example, a footnote on page 173 could be relevant to your application but not to others.

You stitch these devices onto a printed circuit board, manufacture a few prototypes, and test them.

We always advise only making a handful of prototypes. Do not, under any circumstances, make hundreds of these, even if your project is late. They will be wrong, and you will have to modify them. There will inevitably be some problems.

You want those prototype boards in the hands of the engineers as fast as possible so they can test them and then work out design solutions. If there’s any strange, unexpected behaviour, it needs to be understood because it will come back to haunt you at some point during the development process.

When every piece of functionality has been tested on the A model, you can move to a B model, which incorporates all the changes you’ve made and all the problems you’ve identified and gives you a far more solid base.

At that point, you might wish to make additional prototypes to potentially get into the hands of users, and indeed for your development teams.

From here, you’ll be looking at getting your prototype into scale-up and production. You may wish to produce some new product introduction models. While you’ve got a B model designed for production in mind, your manufacturer might need some tweaks and adjustments to ensure they can produce the product effectively.

How to Design a Prototype Demonstrator Model

For a prototype demonstrator model, you must determine what you want to demonstrate and why.

Do you want to prove the functionality works? Or are you looking to go down the MVP (minimum viable product) route where you want user feedback? Regardless of your intentions, these questions must be considered to ensure you do things for the right reason.

Ultimately, you need to nail down the specific purpose of your demonstrator model and do that. Don’t try to do everything in one go.

Why You Shouldn’t Put an A Model into Production

A model prototypes are highly likely to have something wrong with them.

For example, perhaps the specification has changed. You might realise that this product iteration isn’t what you really want. This realisation can come after you’ve shown it to a user or made the prototype and put it on the workbench.

But it would be best if you also considered that there will be changes in the electronics themselves.

Device values will be amended between the A and production models, printed circuit board tracks may also be altered, and you may even make changes to the device itself. It would be best if you considered the ongoing global semiconductor shortage, which could force you to design one chip out and another one in, depending on availability.

Because of this, ordering many A model prototypes for production can be incredibly costly.

Critical Differences Between Electronic Prototyping and Scale-Up

Prototyping proves you can make a few models that demonstrate the right functionality and behaviours in a benign environment. They’re usually tested in a lab environment that’s likely to be air-conditioned. Testing often occurs with users who know how the product should be used or have worked out the use cases, which adds an unintended bias to how the product is tested.

There’s a significant difference between having a handful of prototype demonstrators and scaling up to high-volume manufacturing. At the manufacturing stage, you must have resolved problems associated with temperature, variations, tolerances, and usability.

Somebody, without prior knowledge of use cases, will do something that you never thought they would, and that will break your device, “That’s often me! If someone gives me a product to test, I can pick it up and break it in a few minutes!”

The critical point is that the test and validation, the scale-up stage, includes compliance and quality control considerations. Having peace of mind that every batch off the production line will be okay is vital to preventing many product recalls and customer complaints.

Once you’ve tested the product yourself, over the range of temperatures it’s advertised to perform at, and with end users, you’ve got a product you can consider shipping.

Skipping this crucial stage will create a whole world of pain.

Fletcher’s Law of Prototyping

‘Fletcher’s Law’ is a bit tongue-in-cheek, but essentially, it says that the higher the number of prototypes initially made, the worse the product and those prototypes will be.

This is usually due to cultural or environmental pressures. It is typically the result of businesses compressing the product development process to get a product out of the door ASAP. In short, it is a culture of trying to do as much as possible, in as short a time as possible, to meet a fixed launch date.

Sure, the product might be launched on time, but this usually means that the design, prototyping, and testing have all been rushed. Because of this, crucial steps such as a design review may also have been skipped to save time.

Because of this, you’re saddled with poor-quality prototypes, and all these prototypes now need to be hand-modified, with components added and removed, PCB tracks cut, soldering, and more.

This means that your engineering team wastes time modifying boards that go out for test instead of working on testing and getting your prototype closer to a B model standard that would take your product to market in a reliable fashion faster.

Fletcher’s Law acknowledges that rushing actually slows you down. You spend more money, and while you feel like you’re making progress, you’re just wasting time and money.

Electronics prototyping is not like writing code. You can’t just compile it and get away with it. There is a lead time to get components, which is currently extensive due to the global chip shortage.

Next, you’ve got to manufacture and test them. So, every time you do a PCB prototype, you can lose up to 2, 4, 6, or even 8 weeks. You are better off focusing on getting the quality right on the first run and scaling up.

Want to know more?

If you’re considering your next prototype, why not get in touch for a non-salesy / no obligation chat?
We’re never pushy, always interested and happy to talk shop.