How to make a working prototype of an electronic device

We continue to publish articles on the development and production of sophisticated modern electronics. This time we will tell about the manufacture of prototypes and prototypes. Any project includes this stage, the further fate of the device depends on its results - output for mass production or sending for revision.

The working sample embodies the results of the work of engineers, programmers, industrial designers and technologists. His feel, review and evaluate, comparing the expected with the actual.
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Why do we need these prototypes? How many pieces do you need to make within the project and how much does it cost? What documents are needed for the production of prototypes? You will find answers to these questions under the cut.

1. Prototypes: what is it and why is it even needed?

The prototype (prototype) is a full-featured model of the device, made in full size and as close as possible to the mass product. The main question that the sample allows to answer is: did you manage to technically implement your idea in a real device?

A prototype is created for testing software and hardware, checking for collection, final selection of materials and components, as well as for estimating parameters that are impossible or difficult to assess "on paper" (tactile sensations, usability, weight, body marzime, etc. .).

The samples are also used for passing pre-certification tests, functional testing, electromagnetic compatibility analysis, strength and climatic tests. They can be shown to potential investors or to be evaluated by users.

2. What is the prototype device?

It is necessary to distinguish between these two concepts:

Sample (prototype) device = electronic components + printed circuit board + installation + software installation + case

Product prototype = device prototype + cables / power supplies + packaging + documentation + accessories

With the release of a new product, as a rule, from 4 to 10 different types of prototypes are manufactured: from rough mock-ups made by hand to detailed detailed full-featured devices with all the necessary accessories. In this article we will talk about working samples (prototypes) of electronic devices.

3. How to assess risks and plan a budget for sample production?

It is important to take into account possible risks and rely on at least two iterations, because you are working with a new device that has not been previously performed. Another layout, element base, body - all this requires new solutions in the design.

When working with the first version of the prototype, you may encounter problems. For example, you do not like the characteristics of the device, so you decide to modify them; or you are using a new processor, with which no one has worked before, and when testing it, errors will be revealed. All possible risks and force majeure situations cannot be foreseen even with the most careful planning.

Any modifications to the device and adjustments in the design documentation (CD) will require new prototypes to verify the consistency of the idea, debug assembly technology, etc. If you do not work out all these moments at the sample stage, then similar problems can be encountered in the production of the installation batch, and these are delays in the project timeframe and a significant increase in unplanned costs.

Prototyping is a more laborious process compared to mass production. Therefore, the cost of the prototype can exceed the costs calculated for the device in the series, ten or more times.

4. How many prototypes do you need for the project?

Usually requires no more than 10 pieces. If the device is needed for the work of programmers, 5–7 samples will suffice. If for load tests - you may need more than 10 "experimental" devices.

The minimum number is 3 samples, and better than 5. These figures are determined by the production technology of prototypes, they have a lot of manual work, the probability of marriage is high. For example, you made five devices, three of them earned, two did not. Accordingly, the cause may be a defect in production, and not a mistake of the developers, since the manufacture of a small number of new electronic devices requires debugging of technological processes.

Three / five samples are also the optimal number of devices for testing. They can manifest themselves in different ways: the first has interruptions in power, in the second the USB interface does not work, in the third problems are not found. This indicates mounting problems (soldering). Several samples allow you to collect more statistical data on the deficiencies (this can be either a production defect or a developer error).

Another factor that influences the number is the use of images in the work of various specialists. The programmer debugs software on them, the engineer checks and adjusts the characteristics, the tester evaluates the performance, etc. In the process of intensive use, the risk of damage to the device increases: it can be dropped, broken during assembly, improperly connected to power, etc. The more samples there are, the less you will be exposed to risks and will be able to get the desired result in the planned time frame.

It is also important to consider the number of professionals who will work with devices in parallel. Plus, provide one sample for the customer who can pick it up for demonstration to investors.

And the last factor is when multiplexing printed circuit boards, when components are mounted for several boards at once in one iteration, the cost of manufacturing one or five boards may differ slightly.

5. What documents are needed for prototyping?

Below is a list of documents that you will need to order the production of prototypes:

• For the production of printed circuit boards: project files in any format (preferably Gerber RS-274-X) and an accompanying document indicating the dates and quantities.
• Files for the purchase of components: the PTO (material list) with an indication of the nominal, type of housing, name (Part number) and manufacturer, it can also be PE (list of elements) or specification.
• For a prototype case: an assembly drawing or a 3D model of the case as a file in STEP format.
• For installation: assembly drawing, PnP-file (pick and place), designed for the equipment of automatic installation of components on the board, with an indication of the nominal, housing, reference designation and coordinates of the center of the components.

Naturally, the more detailed documentation you provide to the manufacturer, the better. The main thing is that all information be systematized and backed up with cover letters, they will allow you to build a transparent process of interaction with the contractor, track deadlines and get the expected result.

We hope these tips will help you launch your project and get high-quality prototypes of electronic devices the first time!