What is a Prototype PCB?

Electronics have become such an important part of our daily lives that it’s difficult to imagine a world without PCBs. From our mobile phones and smart watches to satellites and massive machinery, PCBs are virtually everywhere, and they range from small and simple to massive and sophisticated. For some PCBs, the primary design considerations are simply the size you have to work with, the quality of components, and the goal you have to achieve with the circuit. However, for more complex circuits, both designers and manufacturers have to focus on aspects like thermal dissipation, signal integrity, and several other physical and electrical characteristics of the circuits. This is one of the reasons why some of the most complex PCBs aren’t designed and manufactured in one go, and they often start life as prototype PCBs. 

Prototype PCB – From Design To Product

Prototype PCB, as the name suggests, is the first of its kind or a preliminary version of a new design that is created before the PCB can be mass-produced or produced in the desired numbers. However, before we dive deeper into what a prototype PCB is and how it influences the design, manufacturing, and fabrication process, there are a couple of misconceptions about the prototype PCB that should be clarified.

• A prototype PCB is the first complete iteration of a PCB design but that doesn’t necessarily mean that it’s incomplete or developed with less effort than required for the final design. A prototype PCB might be ordered after extensive designs, redesigns, and back and forth between designer and manufacturer/fabricator. In many cases, the prototype PCB may end up becoming the final design as is or after some relatively small modifications. 
• While a prototype PCB serves as a proof-of-concept, that’s not its only role. Creating a prototype PCB can equip the designer, manufacturer, assembler, suppliers, and other stakeholders involved in the process with important knowledge about the PCBs production and life cycle. From availability of necessary parts to cost of manufacturing, every bit of information gleaned from the manufacturing of a prototype PCB can be beneficial in the mass production or subsequent production step.

The creation of a prototype PCB is something both the designer and manufacturer can decide upon. Even after extensive research and multiple design iterations, the designer may not be completely confident about how a PCB will turn out “in the flesh,” so they may go for a prototype before finalizing the design. But even if a designer is completely confident about the design, the manufacturers and assemblers may recommend going with a prototype PCB first so they could have an accurate assessment of the time, effort, and resources that would be needed to mass produce the PCB. It may also help them with decisions like creating specific molds, templates for vias, and ordering some parts in mass. 

Quick-Turn Prototype Manufacturing and Its Benefits

Going for a quick-turn prototype is actually one of the main benefits associated with the “prototype” route of PCB development. There are many manufacturers and assemblers that offer quick-turn PCB prototypes, i.e., in a matter of days instead of weeks. This allows the designer to receive their PCB prototype in a relatively short amount of time so they can start enjoying many of the other benefits of a PCB prototype. This includes (but is not limited to):

Identifying Design Flaws In Early Stages

When a designer requests a quick-turn prototype from a manufacturer, and the manufacturer goes into production mode right away, they may identify flaws and problems in the design that may either prevent them from starting the manufacturing process or rethink the original cost and delivery assessments. Some of these design flaws may be rectified on the manufacturer’s end (after informing the designers), while for others, the designer may have to send another iteration. Either Way, many of the design flaws are caught early, often mere hours or a few days after the design is shared with the manufacturer. But it’s worth noting that this benefit is more clearly evident in quick-turn PCB prototypes than prototypes that may follow a slow or delayed production schedule. 

The main benefit of this early identification of design flaws and in prototype stage instead of the actual production stage is cost. Instead of discarding multiple PCBs or making changes in them post-production to rectify the issues, which may undermine their quality or longevity or may cost a significant amount, the prototype can be scrapped and redesigned using the knowledge of the flaws. 

Testing The Final Product

There is only so much you can test and predict in the design phase of the PCB, and many limitations and problems are revealed only once you have the final product in hand. Some of these may be inherent in the design, like Electromagnetic Interference (EMI), signal integrity, heat dissipation, or minute variations in power or signal output based on different operating conditions. Others may stem from slight design modifications that the manufacturer has to make to quick-turn PCB prototypes, which may include via placement, trace width changes, etc. In any case, having the final product in your hands in a matter of days after you share the design (assuming you are going for a quick-turn prototype) can give you ample time to test the final product in a variety of operating and environmental conditions. You can test the electrical and thermal characteristics of the product, its performance, signal integrity in the replica of the environment it will be working on, and several other things. You may even test for its mechanical integrity, analyzing its performance after subjecting the prototype to vibrations and jerks. If any unwanted test results warrant a redesign, you may make the necessary modifications and get another quick-turn PCB prototype delivered to you to ensure that the new design doesn’t have the same flaws. 

Identifying Manufacturing Challenges 

This benefit manifests whether you are going for a quick-turn PCB prototype or a prototype developed on a typical schedule. In both cases, the manufacturer will be able to identify several things that might be improved in the mass production stage. Note that if you have adhered to the best Design-for-Manufacturing DFM practices and the manufacturer’s design recommendations, the manufacturer may not have any problems producing your design. But that doesn’t mean there is no room for optimization. You may be able to reduce the cost of each PCB unit produced by simply eliminating certain vias, growing or reducing the size of the PCB, opting for different materials, etc. But in most cases, one of the most important benefits of a quick-turn prototype or a regular prototype would be the identification of manufacturing challenges, like the need to run multiple drill iterations on a single PCB layer or certain vias being too close to each other for conventional drilling. 

Identifying Assembly Challenges

A quick-turn PCB prototype or a regular prototype will also reveal any assembly-related challenges that might arise. The most common challenges include not taking the entire package size of a component into account while designing or designing for an older package’s dimensions, whereas a newer, differently-sized package is available in the market right now. It may require certain design adjustments or a complete redesign of the PCB. If the issue is identified in a prototype, the designer, manufacturer, or assembler can come up with the best course of action to rectify the issue, whether it’s opting for different components or a complete redesign of the PCB layout. 

Accurate Cost Assessment

Designers get a reasonably accurate quote when they order a quick-turn PCB, and even though the price of producing a single PCB is significantly different from mass production and includes a lot of duplication of effort, the cost of mass production is easy to extrapolate from the original cost. However, quick-turn PCB prototypes give both designers and manufacturers more insights into reducing or minimizing the cost of these PCB units. They identify areas where small adjustments, like switching from laser to conventional vias, replacing blind vias with through holes, reducing tolerances, or adding/subtracting layers, might significantly lower the cost of production. But that’s more than just a prototyping benefit; it requires proper communication between the designer and the manufacturer. 

Supply Chain Issues

Lastly, quick-turn PCB fabrication (for a prototype) may inform both manufacturer of the PCB and designer about potential supply chain issues. They may learn how difficult it can be to get a hold of certain components or materials to make the PCB. So before mass production, they can either order these in bulk or switch to more easily available materials. It can also help them develop more realistic expectations of delivery timelines and costs. 

These are just some of the many benefits of going with a PCB prototype first before ordering the PCB in the requisite numbers. Quick-turn PCB fabrication (for the prototype) may enhance these benefits by offering the necessary information to all relevant stakeholders as early as possible. 

Quick-Turn PCB Fabrication and Prototype Challenges 

Quick-turn PCB fabrication (for prototype or mass production) may enhance the benefits a prototype offers but it’s also important to understand its limitations as well. Most of these limitations are associated with how the prototype is fabricated and how comprehensive the communication between designers and manufacturers/fabricators is.

• A prototype, whether you are going for quick-turn PCB fabrication (which may come with an additional cost) or normal delivery, introduces an additional cost in the PCB production. Granted that this cost is far lower than what the designer or manufacturer or any other stakeholder) may have to bear if the problems are identified at a later production stage/mass production stage, but the additional upfront cost is a factor worth taking into account. 
• A PCB prototype may also prolong the production process, though this is something you can mitigate significantly by going for quick-turn PCB fabrication (for both prototype and actual production). Nevertheless, the prototyping stage increases the timeline of final delivery. But just like the cost-benefit, it may actually save time if there are issues that are identified in the prototyping stage that would have been time and resource-consuming in the actual production stage (redesigns, testing, etc.).
• One limitation of prototyping is limited visibility into the supply chain constraints. Many fabricators have a limited quantity of almost all PCB manufacturing materials and a wide range of components in place (sample quantities). If they are able to create the prototype using just their own inventory, it may convey a false sense of confidence in designers and other stakeholders about the availability of certain materials and components, and they are confronted with actual problems when they order the prototype PCB in mass quantities. 
• If the PCB prototype is incomplete, i.e., focuses on specific mechanical and electrical characteristics and components of the PCB, it may not paint an accurate picture of the final product. This is especially true when PCB has to be integrated with other solutions and elements in the final form, like external heat dissipation. 
• If the PCB fabricator doesn’t share insights from the fabrication and assembly process with the designer, including insights that may allow them to lower costs and improve performance with some design adjustments, the benefit of prototyping would be significantly limited. Ideally, both designers and fabricators should communicate extensively about the prototype and its production so that all the stakeholders have ample information on hand before finalizing the design. 

Conclusion

A PCB prototype may seem like an additional cost and time element, but in the long run, it can actually help designers or other stakeholders save a lot of time and cost. It allows for early testing and identification of certain problems in the HDI PCB, giving designers ample time to change their design and come up with a more efficient and better-performing version of the original design. Manufacturers and fabricators can also learn a lot from developing a prototype, including how to adjust their standard processes to make the fabrication of a particular PCB easier, faster, cheaper, and more efficient.