From prototype circuits on bread boards to designing our own printed circuit board (PCBS), it was like getting off the training wheels. There’s a lot to learn about this process, so let’s get started. PCB design is carried out in an electrical engineering (EE) process. EE creates the “brain” of how devices work. Without electronics, you’re left with little more than a pile of metal and plastic.

Things to know before starting PCB design: 1. PCB size – this depends on your product size (or case size). Product dimensions are defined during the electronic engineering design process. You can watch a video about it here. 2. PCB layers – The more layers, the more complex the MANUFACTURE of PCB. (Note: Even a single-layer PCB can be a complex PCB, but here we are talking about the complexity of making a PCB. The more layers a PCB has, the more expensive it is to manufacture.)

Layer 2 is usually used for simple toy products

Iot related products usually have 4 layers

Typically used for floors 6 to 8 of a smartphone or smartwatch.

3. Your PCB manufacturer’s requirements. Be sure to read the guidelines for rhythm, trace size, power isolation, and file naming before you start designing.

Information you need to provide to PCB manufacturers:

Number of layers (e.g. 2, 4, 6, etc.)

Materials (FR-2 (phenolic cotton paper), FR-3 (cotton paper and epoxy), FR-4 (glass fiber and epoxy… Etc.)

Thickness (0.5 mm, 1.0 mm… Etc.)

Color (red, black, green… Etc.)

Surface treatment (ENIG (chemical nickel/gold immersion), DIG (direct gold immersion), OSP (organic solderable preservatives, etc.)

Copper weight (1 oz (35 microns), 2 oz (70 microns), 0.5 oz (18 microns)… Etc.)

Gerber file

PCB design process:

Circuit design

For this step, you need to create the schematic. This is a document, like a blueprint, that describes how components relate to each other and work together. To create the schematic file, you will need a software tool. We like Quadcept because it is optimized for designing PCBS for manufacturing (for example, you can export a Bill of Material (BoM) directly from the tool) and is cloud-based, so it can be easily used anywhere. (They also offer a free community version of the tool for manufacturers and students.)

There are many other options you can choose from:

Altium

ExpressPCB

Frequency device

KiCad

Cadence allegro

mat

Computer aided design

DipTrace

After you install the selected tools, you need to obtain the component specifications for each selected component. They can often be found on the supplier’s website. The model file will help you draw the schematic. This component becomes available in the database when you upload the model to the software tool. Then, all you have to do is follow the data manual and connect the wire to each pin in the component. (Note: the details of the design process will depend on the software tool chosen).

Each schematic symbol needs to have an associated PCB space area to define the physical dimensions of the component and the location of the through holes on the brazing pad or PCB. You should have selected the components (or are now selecting them), and we describe this process in the EE Design Process video (see video).

Example diagram

A good schematic is really important, as it will be used as a reference document during debugging and is a good communication tool with other engineers. In addition, the manufacturer can test the device through the test points on this document.

PCB layout + Gerber file

To design the PCB layout and create Gerber files, you can use the same software tools we mentioned in circuit design. Unlike a schematic, a PCB layout assigns the actual components to exact locations on the PCB and shows the tracks that connect each component together between the PCB layers. As mentioned at the beginning of this article, the more layers, the more complex the manufacturing required, and the higher the cost.

Divide the PCB into logical parts based on functions (e.g. power supply, audio output, etc.). Then, be sure to group the components of each section into the same area. In this way, you can keep the conductive trace short and reduce noise and interference.

The user interface (UI) also needs to be kept in mind when designing a PCB. Components such as audio jacks, connectors, leds, etc. need to be adjusted to achieve the best user experience.

Once the layout is designed, a Gerber file is generated. Your PCBA manufacturer will use this file. There are many companies that offer these services, and from HWTrek’s expert library we recommend Kingbrother, NexPCB, and HQPCB.

Sample Gerber files

The placement of components on the PCB is very important. Some components can interfere with each other and cause unexpected behavior. For example, if you have both Bluetooth and Wi-Fi modules, they have the same 2.4ghz bandwidth and can interfere with each other if incorrectly placed.

PCB production

When you send the Gerber file to the PCB manufacturer, they can print the board. This will be the basis to further build the foundation for adding components to the PCB and manufacturing the PCBA (printed circuit board assembly).

Unassembled PCBS

PCBA (Assembly)

Material preparation

At this point in your EE design, you should have selected the components. You can ask the PCBA manufacturer to order the required components for you, or do it yourself if you choose a supplier. Matters needing attention:

Lead time: As these components come from different suppliers, keep the lead time in mind. For some components, it can take up to 8-16 weeks.

Packaging: Order components from reels that are automatically picked up by SMT machines instead of packaging them individually.

Minimum order quantity: Check the minimum order quantity of the component. If you purchase less than the minimum, make sure the selected components are in stock. For small batches (up to 50), you can order online from DigiKey or Mouser. For more quantities, please seek advice from your manufacturer.

Loss: Order 10% more to cover loss (not for expensive components)

Install components on the PCB

There are two main ways to place components on a PCB surface:

Through-holes (through-holes) are manual methods of assembling assemblies with wires into holes on the surface of a PCB. It is also commonly known as DIP or dual in-line packaging process. (See SMT in progress in this video)

SMT (surface mount technology) is the most widely used method in mass production. It is done by fast, accurate SMT machines that save you time, money and avoid human error.

Things to remember:

Your component type number must not exceed the number of reels that the manufacturer’s SMT machine can support.

Optimize and consolidate your components so that only one SMT runs.

Check manufacturer supported footprint pad sizes. Otherwise, the SMT machine will not install components correctly.

Some larger components cannot be installed by machine and still require manual through-hole work. Therefore, both technologies can be used on the same board.

Any components you need to manually add via the through-hole method add to the manufacturing cost.

Reflow soldering

Reflow soldering is the process of making components “stick” to the PCB. The PCBA heats the circuit board through a reflow furnace or an infrared lamp until the solder melts, thereby permanently attaching the component to the circuit board.

The trickiest part here is not to overheat or damage the components, because the thermal characteristics of each package are different. A reliable PCBA manufacturer will be responsible for this process, and all you need to do is provide them with component specifications.

Reflux process.

Other welding methods:

Wave soldering is mainly used for manually added components by the through-hole method. In this case, your PCBA will first go through the reflow welding furnace, and then manually add other components after it will go through the wave soldering machine.

Iron welding can be used for specific situations, but not for mass production.

Testing and quality inspection

In this step, PCBA samples are tested to ensure quality. Common errors are: short circuits in disconnected components, misaligned components and parts of the circuit that should not be connected. The most common tests:

ICT (Online testing). When designing a PCB, some test points are usually reserved for debugging, programming, and other purposes. The ICT machine will use these test points for open/short circuit testing and check that the values of the passive components (resistors, inductors, capacitors) are within the specification range.

AOI (Automatic optical inspection). Manufacturers use a “gold sample” (reference PCBA) to compare with other samples. For this test, the hardware creator will need to provide specifications and tolerances to the manufacturer to set the parameters.

X ray. The PCBA manufacturer will use X-rays to check the welding conditions of the BGA (ball Grid Array) components. Watch the X-ray test in this video.