How to Make a PCB Prototype?

Like most other creative endeavors, creating a PCB starts with an idea. However, the idea is rarely "circuit-first." In most cases, someone is tasked to make a PCB to serve a specific function, and the PCB design is confined to that function. It may also be confined to the specific physical dimensions of the device under which it's supposed to serve. These restrictions and the function of the circuit govern how it's designed and developed. In some cases, both designers and PCB manufacturers have a lot of leeway and flexibility, while in others, they may have to design/manufacture a PCB within a set of restraints. But even when they come up with what seems to be the perfect design, it's usually a good idea to first get a PCB prototype developed for proper testing and identification of flaws that cannot be predicted at the design stage.

Benefits of PCB Prototyping

Before we dive into the steps and good practices of making a PCB prototype, it’s important to understand the benefits of PCB prototyping.

The most significant benefit is that a PCB prototype, especially if you are getting the whole PCB made and assembled, can be fully tested. You can test it for its desired purpose, its electrical characteristics, and even its performance in specific environmental conditions like high heat or humidity.

A prototype may also reveal certain unforeseen problems in the manufacturing or assembling stage. Even if you have designed the PCB for manufacturing and have adhered to the fabricator's recommendations, there might be unexpected problems, like too tighter tolerances for some vias or component placement that doesn’t take into account the 3-D area available.

Developing a prototype can also help manufacturers and assemblers identify several useful and beneficial insights for designers that may allow them to modify the design for better results, lower costs, or both.

Most importantly, PCB prototyping can help designers identify any major flaws early on in the process, which they can rework before the actual production. This may save time and cost in the long run.

What Should Designers Understand About PCB Prototype Services

Understanding what PCB prototype service is, what it entails, and how to fully leverage it can help a designer draw out the maximum benefits from PCB prototyping. A PCB prototyp service may differ from one PCB manufacturer to another. For some, there might be no difference, and the manufacturer/fabricator would treat a prototype PCB the same way they would a normal PCB manufacturing job. However, some manufacturers may offer PCB prototype services in different ways. The PCB prototype service may have a quicker turnaround time (usually less than 48 hours), the cost might be higher than what it is when you get a relatively large batch/set of PCBs made, but most importantly, they may offer you several detailed insights about the manufacturing and assembling process, i.e., information that may be helpful in revising the design if needed. So, it may be a good idea to seek out a PCB manufacturer that offers dedicated PCB prototype services.

Another thing designers should do is familiarize themselves with the exact nature and scope of the PCB prototype service a PCB manufacturer is offering. Manufacturers may have specific guidelines and recommendations for prototype designing in addition to their usual PCB design guidelines about tolerances and file formats. In addition, designers should adhere to the following best practices when designing a PCB prototype:

• Treating it as the final design. This means checking and double checking everything at the design stage, preparing proper schematics, preparing notes/directions for manufacturers for anything unusual, etc. The goal of the prototype should be to identify problems that cannot be identified in the design stages.
• Whenever possible, use standardized components for the PCB. Even though many prototype PCB manufacturers have a comprehensive collection of components, including relatively rare ones, it's the same for materials used in the PCB, but unless a non-standard/rare component or material is a design requirement or serves a specific purpose, make sure the prototype uses standard materials and components. Because when you are mass-producing the same PCB, the cost and additional effort of using non-standard components and materials may be amplified based on the number of units needed to be produced.
• Adhere to the prototype PCB manufacturer's guidelines and recommendations for design, including tolerances they are comfortable with, hole diameters, via/component placement, bend angle for flex/rigid-flex PCBs, etc. This design-for-manufacturing (DFM) approach will ensure you will not waste time reiterating the prototype design.
• Keep tolerances only as tight as absolutely needed, and whenever possible, leave some breathing room in the design/layout. If your design is too "tight," you may have a harder time modifying it after the prototype reveals problems like needing larger capacitors or relocating a particularly large component somewhere else on the circuit. These recommendations might come from the prototype PCB manufacturer, or you may glean from your prototype design, but either way, they would be much easier to accommodate if you have a relatively roomy layout. Otherwise, you may end up relocating and adjusting several other components, traces, and vias just to get enough room.
• While designing the prototype, keep thermal management, mechanical integrity of the design, and signal integrity of the board in mind. If you delay it for a later design iteration, you may end up changing more than you originally intended.
• Design from the perspective of testing. That's the primary directive of a PCB prototype, so leave as many test points as needed and ensure enough room for labeling components (silkscreen) so you know what is when your circuit is finally completed.

While this may not apply to every circuit and every designer, in some cases, it might be useful to design a prototype with multiple iterations in mind. Each PCB prototype and assembly iteration may take some time, but for complex circuits, it may be useful to get the functionality hammered down first and then focus on the electrical and mechanical integrity of the circuit. So, for each PCB prototype and assembly iteration, make sure to focus on the current and all previous elements you tested it for (ensuring nothing old gets compromised for the new things you are testing for.)

Prototype PCB Manufacturer - Good Practices and Guidelines

There are several good practices and approaches that prototype PCB manufacturers should adhere to as well to make prototyping beneficial for all entities involved in the making of the PCB prototype.

The most important rule that a prototype PCB manufacturer must follow here is communication. They should communicate everything necessary regarding the prototype PCB, whether it's their manufacturing capabilities, design requirements, or tolerances, they are comfortable with, before they receive the designs. Once they have the designs in place, a good manufacturer will note every insight they may have about the design and how it might be improved, which will be communicated to the designer later. In some cases, they may communicate certain recommendations to the designer right away so they can be realized in the first iteration of the prototype.

Then, there is the manufacturing process itself. Insights like reducing the number of layers while increasing vias or increasing the surface area of the PCBs can be really helpful for the designer. Communicating these recommendations and the rationale behind them to the designer can equip them with the information they need to improve the prototype design.

Prototype PCB production also requires manufacturers to adhere to top quality assurance standards during development and testing. The idea is that as much information as every stakeholder has about the prototype and its manufacturing, the better. To this end, manufacturers can also offer comprehensive testing services along with prototype PCB production so that the designer has as much information as possible.

It's also a good idea to be more flexible when it comes to feedback. Instead of asking the designer to send over revised design iterations, the manufacturers responsible for prototype PCB production may choose to send over design recommendations that they can incorporate into the current or next prototype right away. This saves time, and since it would be from the prototype PCB production/fabrication lens, production may be easier and more efficient going forward.

Each deviation, change, recommendation, supply chain challenge, and alternative may be documented. This will ensure that the designer knows about every weak point or vulnerability during the prototype PCB production they may fix before ordering the final circuits in the desired quantity.

Finally, it's a good idea to keep the turnaround time on prototype PCB production as quick as possible. This gives designers more time to test their final circuit and considerably reduces the timeline of overall production.

PCB Prototype and Assembly

When it comes to PCB prototypes and assembly, the general idea is the same as before - offering as much information to the designer as possible and generating as many insights from PCB prototyping as possible. Anything, from a small reduction in the PCB form factor to component arrangement at the final assembly, can lead to a huge benefit for every stakeholder when PCB moves from prototyping to actual production.

A PCB prototype and assembly may be created under the same roof if the manufacturer offers both fabrication and assembly services. However, if the two parts of prototyping are done separately, the designer may receive two different sets of recommendations and insights about the design. The manufacturer may inform them about the challenges they face in developing the PCB board, which may cover elements like drilling, layout, coverlay, etc. In contrast, the assembler might focus on things like the form factor of components to be placed, their electrical, thermal, and interference characteristics with neighboring components, and the performance of the final circuit.

Making A PCB Prototype

One thing that every stakeholder involved in the development of a PCB prototype should understand is that it's both similar to and different from the final product. The designer should design a PCB prototype like it would be the final circuit (unless they are planning on making multiple prototypes), but they should also leave room for testing and space for modification. The manufacturer should treat it as a learning process, and the goal shouldn't just be to produce a viable PCB based on design but also to think about how it can be improved from a manufacturing perspective. The assembler shouldn't simply focus on finalizing the product but should also consider how its layout, component placement, and component density might be approved. This may include everything from recommending different component packages to reducing/increasing the number of certain components to optimizing the performance and electrical/thermal characteristics of the final product.

In addition to the "testing" lens, another lens through which different stakeholders should see prototype PCB is efficiency. Make sure that everything that can be identified and tested before the prototype is made is identified and tested. This is relevant to designers and manufacturers, who may assess the design before putting it into production. If they can identify certain problems at that stage and change the design before the first prototype is produced, there might be fewer problems to identify and test in the prototype, and as a result, the redesign might be less extensive and may require fewer redesign iterations.

Conclusion

It's important to understand that even though you have more leeway when it comes to mistakes in the prototype than you would have in the final PCB design, the goal should be to avoid these mistakes in the first place. A well-designed prototype allows you to test for challenges that exist in the final PCB despite the absence of any design mistakes. They may be environment-related or associated with some design limitations that you might not be able to foresee in the design stage. If you make a PCB prototype that requires no modification and changes and can just be mass-produced as is, it can be a major win from a design and production perspective.