PCB Prototyping 101: A Beginner’s Guide to PCB Prototypes, PCB Prototyping Process and PCB Prototype Manufacturers

1. What is PCB?

• 1.1 PCB Fabrication Vs. PCB Assembly
• 1.2. Types of PCBs
• 1.2.1 Single-side PCB
• 1.2.2 Double-side PCB
• 1.2.3 Multilayer PCB

Print circuit boards (PCB) are found in nearly all electronic products you can think of. PCBs have electrical components that are assembled to form an electrical circuit. PCBs act as the command center of electronic devices.

The use of PCB in electronic devices did not take off until the mid-1950s, and it was a game-changing improvement going from wire wrap and point to point construction, allowing mechanical and electronic devices to become smaller in size.

As the world’s dependence on digital and electronic devices dramatically increases, PCB demands are expected to exponentially grow in the years to come. Today, PCBs are becoming smaller while being able to do much more.

In this article, we will discuss the basics of PCB prototyping and the preparation before the PCB prototyping process begins, including the popular PCB design software and PCB fabrication specs. We will also explain the advantages and disadvantages of in-house and outsource PCB prototyping. Later down the article, you will get to know the step-by-step PCB prototyping process and how to choose a PCB prototype manufacturer.

1.1 PCB Fabrication Vs. PCB Assembly

Before we go deeper into the PCB prototyping process, let us demystify the commonly misused and often interchanged terms in the PCB manufacturing world–PCB fabrication and PCB assembly (PCBA).

PCB fabrication refers to the production of printed circuit boards. PCB assembly, on the other hand, involves soldering of components onto the boards and could either be surface-mounted or through-hole.

1.2. Types of PCBs

PCBs are manufactured in three different types–single-sided, double-sided, and multilayer. The size, complexity, and functionality of your PCB design determine how many layers should be used in one board.

1.2.1 Single-sided PCB

Single-sided PCBs is the simplest type as it only has a circuit on one side of the substrate.

1.2.2 Double-sided PCB

Double-sided PCBs are more complex than single-side PCBs since the circuit or the number of components cannot be fitted on a single side of the substrate, and thus two sides.

1.2.3 Multilayer PCB

Multilayer PCBs are the most complex type of PCB because these are composed of several layers whose circuits are connected via wires and drilled holes.

2. What is PCB Prototyping?

• 2.1 Benefits of PCB Prototyping
• 2.1.1 Ability to Spot Flaws
• 2.1.2 Ability to Test Each Component
• 2.1.3 Streamlined Workflow
• 2.1.4 Cost Reduction
• 2.1.5 Representation of Final PCB
• 2.2 PCB Prototype Options
• 2.2.1 Visual Model
• 2.2.2 Proof of Concept
• 2.2.3 Working Prototype
• 2.2.4 Functional Prototype
• 2.3 In-House PCB Prototyping Vs. Outsourced PCB Prototyping
• 2.3.1 Pros and Cons of In-House PCB Prototyping
• 2.3.2 Pros and Cons of Outsourced PCB Prototyping
• 2.4 PCB Prototyping in China

Where does PCB prototyping fit in all of these? Before a prototype PCB board goes into mass production, it has to go through a PCB prototyping process most of the time.

PCB prototyping can be really useful during the PCB manufacturing process because it is where you are testing multiple aspects of a PCB design before it enters mass production.

As a result, PCB prototyping is a long, tedious process, especially if there are going to be multiple revisions brought by the complexities of the prototype PCB board. So it is always best to start with an inexpensive way to produce a PCB prototype.

Before ordering a prototype PCB board, make sure that the PCB prototype manufacturer or prototype fabrication shop can meet your needs. You will learn more on how to choose PCB prototype manufacturer in Chapter #5.

Before going any further into the PCB prototyping process, it is recommended to split determine the goals of your prototype PCB board based on appearance and functionality.

The goal of a PCB prototype based on appearance, or what is known as a looks-like prototype, is to focus on the physical form or aesthetics of the prototype PCB board. PCB prototyping techniques like foam or clay 3D printing, CNC machining, and injection molding. Meanwhile, the goal of a PCB prototype based on functionality is to resolve any technical difficulties.

2.1 Benefits of PCB Prototyping

Normally, PCB prototyping is recommended if the prototype PCB board will be used for products that are intended to enter the market. PCB prototyping is so important for a lot of reasons.

2.1.1 Ability to Spot Flaws

The main reason why PCB prototyping happens is to detect flaws in your PCB design. Instead of going straight to a standard PCB production run, PCB prototyping gives you a chance to inspect your prototype PCB board for defects and resolve them before entering mass production. And you know what a problematic design that has entered mass production means–an awful lot of money and effort going down the drain.

2.1.2 Ability to Test Each Component

For prototype PCB boards with complex designs, it is imperative to test out all its components individually to ensure they are all fully functional. Check if the prototype PCB board can withstand certain conditions, including power variations, temperature variations, and shock resistivity. Otherwise, it would be a lot more difficult to catch a problem once a prototype PCB board is all done and assembled.

2.1.3 Streamlined Workflow

With your ability to spot flaws and test all components of a prototype PCB board, it makes your workflow more efficient. You are likely going to hit your timelines right.

2.1.4 Cost Reduction

PCB prototyping not only results in an efficient workflow, but it also makes your bottom line happy. By having a prototype PCB board, you are likely going to reduce the cost brought by unnecessary production mistakes, regardless of the volume of your production run.

2.1.5 Representation of Final PCB

Knowing how your standard PCB performs once in full swing is extremely important. And it is only through a prototype PCB board you can gauge the accurate performance, size, design, etc. of your standard PCB. Even in the presence of tolerances in prototype PCB boards, at least you get an idea what a finished PCB works and looks like.

2.2 PCB Prototype Options

There are several kinds of PCB prototypes and each of them varies in purpose in every stage of the PCB prototyping process. Depending on what you want to use a prototype PCB board for, your PCB prototype manufacturer might suggest using not just one PCB prototype but two or three or all of them.

2.2.1 Visual Model

A visual model is used to illustrate the physical form of your PCB design and emulate the standard PCB. Electronically, a visual model does not function as it is only intended to demonstrate and review the design in a dirt cheap way possible.

2.2.2 Proof of Concept

A proof of concept (POC) prototype shows the viability of your PCB design. Not all capabilities of the standard PCB are included but just enough to show that design is feasible.

2.2.3 Working Prototype

A working prototype functions like the standard PCB but not quite like it. It has all the functionalities planned for the final board, but they might be subject to change before entering a mass production run.

2.2.4 Functional Prototype

A functional prototype is intended to be as good as the standard PCB. It should include all characteristics and capabilities designed for the final PCB, which means it must be production-quality already.

2.3 In-House PCB Prototyping Vs. Outsourced PCB Prototyping

The time it takes to create a new product from design to manufacturing is important in an on-demand world. This rings true in the design phase.

Typically, a model is designed and the assembly of a PCB prototype is outsourced to a third-party, sometimes based abroad. Nonetheless, there are factors to consider when running an in-house PCB prototyping or outsourced PCB prototyping line.

2.3.1 Pros and Cons of In-House PCB Prototyping

PCB prototyping is time-consuming. Time is primary driving benefit you will get from doing in-house PCB prototyping.

If your timeline is strict, you might want to consider turning to an in-house PCB prototyping process. In-house PCB prototyping allows you to expedite your fabrication of PCB prototypes from weeks or even months to just a few hours or minutes.

Keeping your PCB prototyping process in-house also means valuable designs are contained within your corners. This protects them from third-party party PCB prototype manufacturers from copying, spreading, or leaking your PCB design.

However, PCB prototyping is a process that requires constant change, redesign, and regeneration. Doing an in-house PCB prototyping process means you will be cutting loose from PCB prototype manufacturers, which means you have to it on your own.

For this process to become as smooth as possible, your in-house PCB prototyping line must be flexible and adaptable to quick changes in the design or sudden integration of new parts and in the most drastic scenario where you might need to restart the PCB prototyping run.

2.3.2 Pros and Cons of Outsourced PCB Prototyping

Outsourcing PCB prototyping, on the one hand, is extremely cost-efficient, especially to an overseas PCB prototype manufacturer. But more than the obvious cost savings, outsourcing PCB prototyping allows for a sharing of more ideas, hypotheses, and tests for your project.

Based on their experience, a third-party PCB prototype manufacturer can come up with multiple testing cycles, experiments, and new product ideas that you might have not thought of or used before.

Unfortunately, part inspection is a difficult task if you choose to outsource your PCB prototyping process overseas. Additionally, outsourcing the PCB prototyping process, especially abroad, can put a damper on your overall process when your prototype PCB board is messed up.

2.4 PCB Prototyping in China

Outsourcing product manufacturing in China has become the standard practice for thousands of companies around the world. But the outsourcing of PCB prototyping in China and prototyping, in general, is still in its infancy stage; it is less common than mass production.

Like all business decisions, outsourcing PCB prototypes in China has its own set of advantages and disadvantages. The only way for the advantages to outweigh the disadvantages is to assess your needs well and take the appropriate steps. If you want to learn more about how to choose a PCB prototype manufacturer, read our detailed guide in Chapter #5.

China is the best country to have your PCB prototype or standard PCB manufactured since it is a fairly affordable place to manufacture, even for prototypes and low volumes. Companies based in the United States, Canada, the United Kingdom, and elsewhere can reduce their PCB prototyping costs by taking full advantage of the economies of scale that have been made to support the massive number of hardware development taking place in the country, especially in Shenzhen, the electronics capital of the world.

To say that China is a low-cost, low-quality market has, to some degree, become a statement of the past. In fact, China spent $1.1 billion on additive manufacturing in 2017, which means its prototyping market is exponentially growing.

Cost reduction and cost savings are the main reasons why companies turn to China for their PCB prototyping needs, making it a market of extraordinary value. However, this value sometimes comes at the expense of quality, so you need to be wary of who you are going to work with.

Also, logistics is still the main problem why outsourcing PCB prototyping in China is a huge disadvantage. On top of that, the protection of trade secrets, trademarks, copyrights, and patents are a major consideration as well, not only when outsourcing in China but when working across borders. And there will be cultural and language problems.

Nevertheless, with the ever-growing manufacturing industry in China, it should not be difficult to find the right PCB prototype manufacturer that can accommodate your PCB prototyping needs and beyond.

3. Preparing for PCB Prototyping Process

• 3.1 Gerber Files
• 3.2 Common PCB Design Software
• 3.2.1 Eagle
• 3.2.2 OrCAD
• 3.2.3 KiCAD
• 3.2.4 Altium Designer
• 3.2.5 PCB Wizard 3
• 3.3 PCB Fabrication Specs
• 3.3.1 Dimension
• 3.3.2 Number of Layer
• 3.3.3 Material
• 3.3.4 Board Thickness
• 3.3.5 Pad Plating
• 3.3.6 Impedance Control
• 3.3.7 Minimum Width/Spacing
• 3.3.8 Hole Sizes
• 3.3.9 Solder Mask
• 3.3.10 Silkscreen
• 3.3.11 Minimum Pitch
• 3.3.12 Castellated Holes
• 3.3.13 RoHS Compliance

After learning all the basics of PCB prototyping and its advantages, it is time to lay the groundwork for the PCB prototyping process. In this chapter, we will walk you through the preparation before jumping into the PCB prototyping process. You’ll get to know what Gerber files are, some of the most popular PCB design software, and the PCB fabrication specifications.

3.1 Gerber Files

Gerber files are the digital blueprints that allow your PCB prototype manufacturer or PCB manufacturer to construct your printed circuit board layer by layer. Many a free and premium PCB design software have built-in tools for generating Gerber files, such as Eagle, OrCAD, KiCAD, Altium Designer, and more. You will learn more about these PCB design software in the next section.

3.2 Common PCB Design Software

A PCB or PCB prototype is nothing without a PCB design software. The success of your PCB prototype in part depends on your chosen PCB design software and how you use it.

It is not an easy task to choose which PCB design software, so in this section, we will introduce you to the most favored PCB design software available on the market today, both free-to-use and premium packages.

3.2.1 Eagle

Eagle is one of the most popular PCB design software out there and this is due to it being free-to-use and user-friendly. The free version allows you to use two schematic sheets, two signal layers, and 80cm² board area. If you need more, you can upgrade to a premium plan, still at a fraction of most PCB design software’s cost.

The downside of this PCB design software is the lack of high-end features that enables users to create an easy layout of high-speed signal designs or other routing features, such as push shove routing. Additionally, its design workflow is a bit dated. But overall, Eagle is a great option for beginners and advanced users who do not need complex designs.

Eagle is available to download on Windows, Linux, and Mac.

3.2.2 OrCAD

OrCAD is one of the more established professional level PCB design software. It offers all high-end features you will need, including 3D modeling, curved routing, group routing, DFM checking, and advanced auto-router.

The number of signal and design analysis tools make it handy for almost all of your PCB prototyping needs. It also has many trim levels, including its free version, OrCAD Lite. Unfortunately, it has a steep learning curve so beginners might find it difficult to use at the beginning.

OrCAD is available to download on Windows, MacOS, and Linux.

3.2.3 KiCAD

KiCAD is open-source PCB design software, which means it is free for anyone to use. It includes a schematic, PCB and component module as well as high-end features found in professional PCB design software, such as 3D modeling, push shove routing, differential pair routing, and hierarchical schematic design.

Since KiCAD is open-source software, it has a large community of users and contributors that provide you support on anything software-related. However, it can be a bit hard to navigate this software due to its unconventional workflow and disorderly modules.

KiCAD is available to download on Windows, MacOS, Linux, and Ubuntu.

3.2.4 Altium Designer

Altium Designer is another popular professional PCB design software. Some of its features include a schematic, PCB module, 3D modeling, auto-router, differential pair routing, and track length tuning.

Unlike most professional grade PCB design software, Altium Designer is easier to use. However, its steep price point and rich feature set might make hobbyist and DIY communities second guess.

Altium Designer is available to download on Windows.

3.2.5 PCB Wizard 3

PCB Wizard 3 is a low-cost, easy-to-use PCB design software that is as powerful as the high-end design suites. It allows you to create single and double-sided PCB prototype designs.

It contains a schematic capture component, PCB component placement, PCB layout component, and auto-router. On top of those, this software allows you to generate various types of manufacturing file formats as well as a bill of materials report. However, it does not have a three-dimensional viewing feature.

PCB Wizard 3 is available to download on Windows.

3.3 PCB Fabrication Specs

PCB fabrication specifications are design requirements that have an immense influence on your product’s cost, supply chain, yield, and manufacturability. Failure to determine PCB fabrication specs could result in a costly PCB prototyping process (and the future product) and low yield.

To help you save time and money in the PCB prototyping process, here are fabrication specs that you might have to chew over. Keep in mind that PCB prototypes might differ a little in specifications from the standard PCB board.

3.3.1 Dimension

It simply is the size of your board. How big is your PCB prototype in size?

The cost of a prototype PCB board scales with surface area, so make sure to use only the space you need in order to cut down on your expense. Note also that prototype PCB board designs with irregular shapes that result in waste materials during PCB fabrication will cost you more than a smaller, rectangular footprint for a similar board.

For a prototype PCB board, the minimum board size is 10mm x 10mm and the maximum is 500mm x 500mm. For standard PCB, the minimum board size is 6mm x 6mm and the maximum is 600mm x 700mm.

3.3.2 Number of Layer

The number of layers in a prototype PCB board indicate the level of complexity it is. More PCB copper layers mean the higher chances of components and pins to cross over one another. Normally, prototype PCB boards have 1-8 layers while standard PCB have 1-32 layers.

3.3.3 Material

Two of the most common type of PCB materials used these days are the fiberglass epoxy, known as the FR-4, and the phenolic paper, known as the FR-2. Other less known types of PCB materials include Teflon, polyimide, and peek (polyether ether ketone).

Glass epoxy is often the default choice of most PCB prototype manufacturers, which has to be carefully thought of if your processes include high-speed or RF boards. A phenolic paper is more toxic and tends to be more prone to chipping and cracking.

3.3.4 Board Thickness

Board thickness is a major mechanical PCB specification. The industry standard for prototype PCB board thickness is 0.4mm to 2.0mm and 0.4mm to 3.2mm for the standard PCB.

However, the number of copper layers dictate the core dimensions of a prototype PCB board and standard PCB based on your desired thickness. Small and tight prototype PCB boards may command a 1.0mm thickness or less.

3.3.5 Pad Plating

Pad plating is a coating method wherein the exterior copper surface of a prototype PCB board or a standard PCB is covered with another metallic material. This technique enhances the solderability of the pads during assembly.

Two most common plating techniques for prototype PCB boards are leaded or lead-free HASL (hot air solder leveling) and ENIG (electroless nickel immersion gold) plating. The former applies solder to the board during PCB assembly, while the latter has more resistance to oxidation and flatness but more expensive.

3.3.6 Impedance Control

For a prototype PCB board or standard PCB that has a radio on it, such as Wi-Fi, NFC, and Bluetooth, impedance control has to be specified. Various factors affect impedance, including solder mask, trace width, and dielectric of the prepreg material. For instance, Wi-Fi antennae circuits are normally controlled to 50-ohm impedance.

Impedance control can only be determined by expensive equipment that not all PCB prototype manufacturers have as part of their service. If this is something you need for your prototype PCB board, you might have to have this service added on top of your PCB fabrication costs.

3.3.7 Minimum Width/Spacing

The minimum width/spacing is the distance between individual copper traces on your prototype PCB board or standard PCB. Many PCB prototype manufacturers can handle down to 3-4 mil spacing, although 6 mil spacing is fairly safe. A prototype PCB board that has sufficient spacing can route out 64 or 128 pins of a microcontroller, which is pretty nifty.

3.3.8 Hole Sizes

Specifying the sizes of the holes and vias on your prototype PCB board is a good way to maximize space. The hole size tolerance of prototype PCB board and standard PCB ±0.08mm – ±0.15mm.

The smaller hole size tolerance means the harder your PCB prototype manufacturer to go through the drilling process. Missing hole size tolerance may mean more wasted materials.

3.3.9 Solder Mask

Solder mask is used on copper traces of a prototype PCB board or a standard PCB to prevent solder bridges from forming and causing short circuits.

PCB prototype manufacturers have a variety of colors to choose from. Green is cheap; white is hard to maintain; black avoids cosmetic defects.

3.3.10 Silkscreen

Silk screen is the final layer of your prototype PCB board or standard board. It contains the text, graphics, and designators to help annotate your board.

This process is appropriately called legend printing, but silkscreen became more popular because silkscreen printing with epoxy ink is the most common technique for marking PCB legends. A higher resolution, more expensive version of silkscreen printing is liquid photo imaging (LPI).

3.3.11 Minimum Pitch

Pitch is the distance between neighboring pins on an electrical component. Normally, the minimum pitch is 0.3mm among PCB prototype manufacturers. Prototype PCB boards and standard PCBs with a myriad of pins that are close to one another and conservative pitch requirements may produce more scrap.

3.3.12 Castellated Holes

Castellated holes are vias and clearance holes that have been cut down a diameter to reveal copper along the side face of the PCB. Integrating castellated pads to prototype PCB board design is recommended if your module or PCB mounts on another PCB. Not all PCB prototype manufacturers can build PCBs with castellated holes, so be sure to consider that.

3.3.13 RoHS Compliance

RoHS (Restriction of Hazardous Substances Directive) compliance is an important consideration that you have to communicate with your PCB prototype manufacturer. RoHS compliancy certifies that your product that is directly sold and shipped to your customers is free from lead and other toxic substances/materials.

4. PCB Prototyping Process

• 4.1 Designing PCB Prototype
• 4.2 Creating Schematic Design
• 4.3 Creating Bill of Materials
• 4.4 Designing PCB Routes
• 4.5 Checking PCB Prototype
• 4.6 Creating Photo Film
• 4.7 Printing Inner Layers
• 4.8 Aligning Layers
• 4.9 Combining the Layers
• 4.10 Drilling Holes
• 4.11 Copper Plating
• 4.12 Outer Layer Imaging
• 4.13 Copper and Tin Plating
• 4.14 Final Etching
• 4.15 Applying Solder Mask
• 4.16 Applying Surface Finish
• 4.17 Applying Silkscreen
• 4.18 Cutting Board
• 4.19 Sourcing of Components
• 4.20 PCB Prototype Assembly
• 4.21 Solder Paste Stenciling
• 4.22 Picking and Placing
• 4.23 Reflow Soldering
• 4.24 Inspecting PCB Prototype
• 4.25 Inserting Through-Hole Components
• 4.26 Functionality Testing
• 4.27 PCB Prototype Testing

Once you have all the requisites, you are all set to begin the PCB prototyping process. A lot of PCB prototype manufacturers can help you with the process. Working with a PCB prototype manufacturer that offers full turnkey solutions can streamline the process since you do not have to deal with multiple companies back and forth.

Your final prototyping goal is to arrive at a production-quality PCB prototype that will look and work like your final, mass-produced prototype PCB board.

PCB prototyping is all about learning. Every time you make a prototype PCB board, you will learn something new.

Begin with the basic and cheap PCB prototype. As you modify bits and pieces of a prototype PCB board, you should be able to come up with a PCB prototype that is as good as the final PCB prototype.

4.1 Designing PCB Prototype

The design is the foundation of the PCB prototyping process. As we said in the previous section, you can take advantage of the free and premium PCB design software to come up with your own PCB prototype design.

It is recommended to start designing a custom PCB if you are quite certain about your PCB’s functionality. A custom PCB prototype can be practical and convenient to build before entering the mass production. If you are looking into creating a custom PCB prototype, there are available breadboards and perfboards that you can buy online.

A breadboard is a solderless board for a temporary PCB prototyping. It has strips of metal under the board and connects the holes on the top of the board.

A perfboard, also called dot PCB, is another PCB prototyping material. It is a thin, rigid piece with pre-drilled holes at standard intervals across a grid. It is usually made of paper laminated with phenolic resin or fiberglass epoxy.

4.2 Creating Schematic Design

Once you have designed the PCB prototype, it is time to come up with a schematic design, which illustrates all the project requirements and goals that PCB prototype manufacturers and engineers will use during the production process.

A schematic design may include information about materials, components, and hardware to be used in production. It will also describe the board’s function, characteristics, and the arrangement of the components. Additionally, deciding on the right panel size and grid is important during this phase.

Producing a schematic design is not a one-off task. It has to go through preliminary checks to ferret out possible errors and rectify them.

After that, the schematic design has to run simulations using a PCB design software to make sure the PCB prototype works well. Once the simulations are good, the electronic schematic design shall be converted into a netlist, a description of the connectivity of the electronic circuit.

It helps to constantly run design rule checks throughout the design process because it gives you the opportunity to rectify defects and errors as you go.

4.3 Creating Bill of Materials

A bill of materials is a list of all the components and materials you need for production of the prototype PCB board. If you choose to contract a PCB prototype manufacturer, they will use this document to ensure they get the right ones.

A detailed bill of materials may include the following information:

• The number of needed components and materials.
• Reference Designators. Codes used to identify individual parts.
• The specifications for each component and material described in the appropriate units, such as farads and ohms.
• Footprint. The location of each component on the prototype PCB board.
• Manufacturer part number. The part number used by the component manufacturer.

Once the bill of materials and schematic design are ready, a layout engineer and a component engineer shall check these and collect the required components and materials. The component engineer is specifically responsible for choosing the right components and materials that will work for the schematic design and meet the cost and size requirements of the client.

4.4 Designing PCB Routes

Design PCB routing by connecting the traces on the board. When designing the routing of the PCB prototype, you need to include a variety of factors like power levels, signal noise generation, and noise sensitivity.

In most PCB design software, the netlist you have previously created is used to plan the routing. In addition, most of them can automatically calculate the most favorable routes based on the number of available layers and other factors.

If ever the PCB routing becomes messy to the point that many routes are crossing over other routes, consider using a two-layer prototype PCB board just to make things systematic and tidy. Dedicate one layer to the east-west connections, the other to north-south connections.

Designing PCB routing can take a lot of time, especially for bigger and more complex prototype PCB boards.

4.5 Checking PCB Prototype

Conducting regular design rule checks throughout the process enable you to take over functionality issues before moving into the fabrication stage. A comprehensive inspection is highly recommended to see every bit of details of your design.

Thermal issues like heat spots are some of the most common problems many run into. It is necessary to keep your PCB prototype’s temperature consistent. Inconsistent temperatures and heat spots are usually caused by features like thermal paths, the size of PCB, the number of PCB layers, and varying copper thickness.

Apart from design rule and thermal checks, you should also include an electrical check (ERC), a layout-versus-schematic (LVS) check, and an antenna check. Once these checks and other quality assurance assessments are done, you can proceed to the next steps.

4.6 Creating Photo Film

Using your PCB prototype design, you or your PCB prototype manufacturer need to create a photo film of the prototype PCB board for each layer and solder mask of the board. The photo film is a plastic sheet printed with a photo negative of the board, which marks the conductive copper and non-conductive copper parts of the board.

4.7 Printing Inner Layers

Copper is then applied to a substrate material. Your PCB prototype manufacturer can do this for you.

In this step, the copper is pre-bonded to the substrate before applying a layer of photoresist. It is then exposed to ultraviolet light to harden the photoresist.

Areas blocked by blank ink from the plotter will remain flexible or melted. They will be removed before the hardened photoresist.

4.8 Aligning Layers

For PCB prototypes with multiple layers, you need to align them and punch accurate registration holes. The alignment has to be accurate, otherwise combining the layers with the inner layers will match.

4.9 Combining the Layers

The outer layer materials called prepreg and the original substrate covered by a copper foil and containing the copper trace etchings are combined.

In the layer-up stage, the prepreg layer is placed over an alignment basin, followed by stacking of the substrate layer, copper sheet, more prepreg, and an aluminum foil and copper press plate.

In the bonding stage, a bonding press computer heats up the stack, applies pressure, and cools the stack. From here, the stack is unpacked by removing the pins and the pressure plate.

4.10 Drilling Holes

Your PCB prototype manufacturer will drill holes into the stack which will be used to add components later. The holes need to be as precise as possible, about 100 microns in diameter.

Your PCB prototype manufacturer will use an X-ray locater to home in on the right holes and a computer to drill them. Drilling prototype PCB boards with more than 100 holes might take a while.

4.11 Copper Plating

Copper plating uses a chemical bath to put down a layer of copper about one micron thick on the panel’s surface. The copper will veil the whole board, including the interior walls of the holes, to cover the fiberglass material of the interior panel. A computer controls this process for precision.

4.12 Outer Layer Imaging

Another layer of photoresist is applied on the panel to image the outer layers with your PCB design. It follows the same process as the previous one and produces an inversion of the inner layers.

4.13 Copper and Tin Plating

Another set of copper plating is done and this time the photoresist layers ensure that the copper only deposits on the desired parts of the prototype PCB board. Normally, the board receives tin plating to protect the copper during the next stage.

4.14 Final Etching

The PCB prototype manufacturer uses chemical solutions to remove any excess copper. With the tin plating, the copper keeps the conductive areas protected. The conductive connections are done after this.

4.15 Applying Solder Mask

Wipe the panel clean, then put an epoxy solder mask ink on it. Expose the prototype PCB board to ultraviolet light to harden the film. Then, remove unhardened parts.

4.16 Applying Surface Finish

Deposit more plating, using either gold or silver to get a surface finish. The PCB prototype manufacturer might use hot air leveling to make sure the pads are consistent.

4.17 Applying Silkscreen

A silkscreen is applied to the surface of the PCB prototype using ink-jet writing that carries crucial information about the board.

4.18 Cutting Board

After testing the PCB prototype’s electrical functions, the PCB prototype manufacturer cuts the separate board from the bigger panel using either a v-groove or a router. This makes it easier to pop the board out of the panel.

4.19 Sourcing of Components

As you enter the PCB prototype assembly phase, you need to obtain all the necessary components. You can do this yourself or a PCB prototype manufacturer can do it for you. Either way, the bill of materials you created earlier will come in handy at this point.

4.20 PCB Prototype Assembly

Once all components and materials are ready, your PCB prototype manufacturer will assemble them for you.

4.21 Solder Paste Stenciling

The PCB prototype manufacturer applies a solder paste to the board, which blends with a flux to help the solder melt and bond to the prototype PCB board surface.

By putting a stainless steel stencil on top of the PCB prototype, the applicator only applies solder paste to the areas where components will be in the finished PCB prototype. It spreads the solder paste evenly to every open area. When the stainless steel stencil is removed, the solder paste should be left in the desired places.

4.22 Picking and Placing

The PCB prototype manufacturer will pick and place machine to place surface mount components (SMD) on the PCB prototype. This tool orchestrates these non-connector components over the soldering paste in preprogrammed areas.

4.23 Reflow Soldering

The reflow soldering process ensures that the solder paste is solidified well to hold the components on the prototype PCB board.

Using a conveyor belt, the PCB prototype will be carried through a reflow oven where a series of heaters to slowly heat up the board to around 480 degrees Fahrenheit, melting the solder in the solder paste. As it cools down, the melted solder solidifies, and permanently sticking the SMDs to the PCB prototype. For PCB prototypes with two sides or multiple layers, stenciling and reflow soldering are conducted separately on each side or layer.

4.24 Inspecting PCB Prototype

Checking for errors after the reflow step is necessary because there are instances that the conveyor belt causes accidental movements. Such movements may cause poor connection quality, electrical shorts, and even complete lack of a connection.

Manual checks, X-ray inspection, and automatic optical inspections are done to ensure quality control of the prototype PCB board.

4.25 Inserting Through-Hole Components

Apart from SMDs, some prototype PCB boards need other components which are called plated-through-hole (PTH) components. They are plated all the way through the board to enable them to send an electrical signal from one side to the other.

Manual soldering or wave soldering is necessary to insert PTH components on the PCB prototype. Soldering paste will not work with these components because it will just pass through the holes without adhering to them. However, wave soldering does not work with double-sided boards.

4.26 Functionality Testing

Functionality testing is the second to the last step in the PCB prototype assembly process. This step simulates the normal operating conditions the PCB prototype will be exposed to.

4.27 PCB Prototype Testing

Before powering up your PCB prototype or moving to PCB fabrication, PCB assembly, and PCB manufacturing, look out for anomalies in your prototype PCB board one last time. It could be short circuits, inverted polarity, populated components, routing crossovers, damaged or missing components, and a lot more.

Testing the PCB prototype according to your project goals and intentions enables you to see design flaws. If you have multiple prototype PCB boards with different designs, run identical tests on the boards and mirror the results. If possible, run the PCB prototype within the product it will power.

5. How to Choose a PCB Prototype Manufacturer

• 5.1 Cost
• 5.2 Quality
• 5.3 Industry Experience
• 5.4 Certifications and Competencies
• 5.5 Equipment
• 5.6 Customer Service
• 5.7 Minimum Order Quantity
• 5.8 Lead Time

Looking for a PCB prototype manufacturer is not as hard as a PCB manufacturer and assembler. But in most cases, PCB manufacturers and assemblers have a PCB prototyping service that you can avail.

As much as possible, choose a PCB prototype manufacturer who will also be your final board manufacturer/assembler. This will save you time going to different service providers back and forth.

In this chapter, we will guide you how to choose a PCB prototype manufacturer. What qualities should you be looking for? What questions should you be asking during the selection process?

We’ve narrowed down the criteria to eight and explained how they could affect your PCB prototype or the PCB prototyping process in general.

5.1 Cost

Production cost is the primary consideration for most companies when it comes to choosing a PCB prototype manufacturer. If in-house PCB prototyping or a do-it-yourself prototype PCB board is not an option, you can reach out to a third-party PCB prototype manufacturer or a PCB manufacturer/assembler.

An overseas PCB prototype manufacturer or PCB manufacturer/assembler could be cheaper if you are looking to produce prototype PCB boards in bulk. The cost of your prototype PCB board largely depends on the PCB prototype manufacturer’s expertise and the type of service required.

For instance, it could or could not cost you a lot of money if you will pass on the purchasing of components to the PCB prototype manufacturer.

When requesting for a quotation from a prospective PCB prototype manufacturer, make sure to examine the quoted price for hidden charges. When you have established a good relationship with a PCB prototype manufacturer, it should not be hard to score perks and discounts such as free tooling cost, etc.

5.2 Quality

The quality of your prototype PCB boards directly affects your end product’s application and performance.

If the quality of your prototype PCB board is already questionable at its development and testing stage, surely your end product will not fly down the line. Therefore, a prototype PCB board should be as good as the final product before entering mass production.

One good way to assess a PCB prototype manufacturer’s performance is to look at its product situation. You might want to ask questions like:

• What statistical process control methods do a PCB prototype manufacturer or PCB manufacturer/assembler apply during the PCB prototyping process?
• Does the PCB prototype manufacturer or PCB manufacturer/assembler implement regular quality administration improvement like quality control circles (QCC) or total quality management (TQM)?
• Does the PCB prototype manufacturer or PCB manufacturer/assembler apply administration of engineering change order (ECO)?
• Does the PCB prototype manufacturer or PCB manufacturer/assembler follow strict quality control assessments such as equipment calibration, material inspection record and administration, file administration, ESD control plan implementation, BOM preservation, SMT (surface mount technology) yield rate, and AQL level?

5.3 Industry Experience

PCBs are used in various products across many industries. Hence, it is hard to find one PCB prototype manufacturer or PCB manufacturer/assembler that covers all industries and are masters of all.

More often than not, these PCB prototype manufacturers or PCB manufacturers/assemblers are serving multiple industries but are only at specific industries. For instance, a PCB prototype manufacturer or PCB manufacturer/assembler for smartphones and tablets are certainly good at producing prototype PCB boards that are space-constrained.

This is why it is so important to know your industry well so you would know what to look for in a PCB prototype manufacturer or PCB manufacturer/assembler. Contracting a PCB prototype manufacturer or PCB manufacturer/assembler that knows its expertise too well will expedite the PCB prototyping process, even with the occasional occurrences of changes.

5.4 Certifications and Competencies

You can tell how competent and well-rounded a PCB prototype manufacturer or PCB manufacturer/assembler is by certifications and compliances. Being competent and well-rounded are the foundation of any companies known to produce high-quality products.

Look for PCB prototype manufacturers or PCB manufacturers/assemblers that are ISO 900:2008-certified (quality management system), UL-approved (product meets specific, defined requirements), RoHS-compliant (free from certain hazardous substances). Choosing a PCB prototype manufacturer or PCB manufacturer/assembler that meet these certifications and other standards, your prototype PCB boards and your future product are in good hands.

5.5 Equipment

It is so important to know the list of equipment your prospective PCB prototype manufacturer has so you would know if they can meet your needs and requirements.

For example, PCB designs that require SMT components should be done by a PCB prototype manufacturer or PCB manufacturer/assembler that has its own pick-and-place equipment, 3D BGA inspectors, reflow ovens, and rework tools.

State-of-the-art equipment alone does not dictate the quality of work to be done, although it is a good indicator. Therefore, equipment is not just about how fancy it is. Whatever is in a PCB prototype manufacturer or PCB manufacturer/assembler’s arsenal, it should give you an idea on the quality of a prototype PCB board you will get and whether you will receive a timely order or not.

5.6 Customer Service

The PCB prototyping process may not be as complex as the PCB manufacturing or assembly itself, but customer assistance from the order stage up to the production is a necessity that customers deserve. Customer service may not seem to have a direct influence on the quality of your prototype PCB board, it definitely has a huge impact on how smooth your PCB prototyping process is going to be.

A great PCB prototype manufacturer or PCB manufacturer/assembler puts the interest of its customers first and provides an open line of communication where they can share their concerns. Since the negotiation process, you should be able to tell by the email, text or call replies if a PCB prototype manufacturer can respond to you promptly.

5.7 Minimum Order Quantity

The minimum order quantity (MOQ) varies on every PCB prototype manufacturer depending on the size and scope of a project. Since it is just a PCB prototyping process, a PCB prototype manufacturer might consider low MOQ, which could be anything from a one prototype PCB board to a dozen.

5.8 Lead Time

Lead time is also necessary during the PCB prototyping process. Doing an in-house PCB prototyping allows you to take control of your progress and process if you are proficient in doing so.

If you are not well aware of how PCB prototyping works, look for a PCB prototype manufacturer that offers full turnkey service–from PCB prototyping up to PCB manufacturing/assembly–to minimize delays in the process. In such a case, you only need to submit your PCB design and the PCB manufacturer/assembler can take it from there.

Take note, however, that outsourcing PCB prototyping domestically or overseas has a massive effect on lead time. PCB prototype manufacturers and PCB manufacturers/assemblers abroad, especially in China, might offer you cheaper options. But if you are pressed for time, contracting an overseas PCB prototype manufacturer might not be a sound decision to make. In this case, domestic PCB prototype manufacturers are the best option there is.

If you want to monitor the lead time of your PCB prototyping process, make sure to choose a PCB prototyping company that offers order tracking service beyond the promise to deliver your prototype PCB boards on time. Most PCB prototyping/manufacturing/assembly companies start the work as soon as the parts and boards become available.

6. Conclusion

PCB prototyping has been proven as an excellent method to avoid PCB design fiasco during the mass production stage. Going through a PCB prototyping process ensures your prototype PCB board is ready for takeoff before moving to PCB fabrication and/or assembly.

Before moving to the PCB prototyping process, you need to have your ducks in a row first. Do this by learning what Gerber files are, which PCB design software should you be using, and the PCB fabrication specs.

Whether you go in-house or outsource when it comes to your PCB prototyping process, weigh the pros and cons. If you want to protect your intellectual property and streamline your PCB prototyping process, go in-house by all means. If you want to save a lot of money, then outsourcing might be the best option to manufacture your prototype PCB board.

The PCB prototype manufacturer is also a key factor in the quality of your PCB prototype, so it is important to find the right one. In Chapter #5, we have broken down all the factors that come into play when looking for a PCB prototype manufacturer that fits the bill.

When choosing a PCB prototype manufacturer and possibly your PCB fabricator/assembler, only you have the final call because only you know your goals and priorities. Sizing up a suitable PCB prototype manufacturer should be based on factors like industry experience, competencies, cost, and lead time, among others.

That is all for the PCB prototyping process. We hope to have demystified it all for you. If you still have questions, leave them in the comments so we can get back to you as soon as we can.