Avoid these BIG 5 mistakes when you start your multilayer PCB fabrication process

Article By : Suresh Patel, Mer-Mar Electronics

Here are five common mistakes that are typically made during the PCB fabrication process and ways to avoid them.

As the demand for miniature and powerful devices keeps increasing, so does the need for multi-layer PCBs. PCBs are certainly increasing in layers as well as in component density. What is important in ensuring accuracy in such PCBs is the design and thereafter its fabrication. Despite the growing use of such PCBs, some mistakes are relatively common when it comes to the PCB fabrication process. We bring to you five common mistakes that are typically made during the fabrication process as also ways to avoid them. With due attention paid to these five aspects, you can ensure that you can avoid costly mistakes and that you do not have to deal with correcting these errors when the electronic device is ready to be sent out into the market.

Multi-Layer PCB Fabrication Process: 5 common issues and how to avoid them

1. Design Complexities

Multiple layers come with an intrinsic complexity in design. The probability of complexity is further increased on account of the demands that are placed by miniaturization.

The two risks that multilayer PCBs particularly deal with in terms of design include:

  • Bows
  • Twists

Let us look at them a little closer. A bow refers to the spherical curve while the twist is a deformation that is seen parallel to the diagonal of the board. In order to avoid bows and twists, the following measures need to be taken:

  • The parameters of the board need to be carefully selected so that the stress on the circuit board can be relieved.
  • The material chosen needs to be RoHS compliant.

2. Selection of Substrate Material

A common mistake in fabricating multilayer PCB is the choice of the wrong substrate material. In choosing the right material, you need to ensure that the material conducts electricity as well as provides insulation between the conductive layers.

Here are the aspects to check for in making the right choice of material:

  • High-frequency substrate materials need to have a small and stable dielectric constant.
  • The substrate should also have high heat resistance, chemical resistance, and impact strength.
  • It should have low hygroscopicity
  • It should provide excellent electrical insulation.

Typically, FR 4 is a popular choice when it comes to the substrate material.

3. Resin-plugged Through Manufacturing 

Resin-plugging is fast emerging as a standard process when it comes to PCBs, especially where there are a large number of layers. Resin-plugging is the go-to process, especially where pressure-filling and green oil-plugging resins cannot provide optimal results. Resin plugging is a preventive measure that helps in securing vias from the unwanted flow of the solder material. However, manufacturers typically face the issue of resin plug holes. This is an issue that needs to be solved with the help of a vacuum plug machine.

4. Heat Dissipation

When it comes to the multi-layer PCB fabrication process, overheating is an issue. What is required is proper heat dissipation methods. There are a number of methods that ensure heat dissipation is facilitated. These include:

  • Convective heat removal
  • Conductive heat removal
  • Use of fans
  • Use of cooling radiators
  • Use of materials that help in heat transfer such as aluminum, copper, magnesium, and more.

5. Back Drilling

Very often, multilayer PCB fabrication comes with issues such as loss of circulation, hole blocking, and more. Back drilling has a very important role to play as a popular PCB manufacturing technique. With the use of the right angle as well as the right manufacturing parameters, these issues can be avoided.

By avoiding the above 5 common mistakes you can ensure reliable and performance-driven Multilayer PCBs.

In addition to the above 5 mistakes, here are some design aspects to watch out for:

  • Look for layout issues such as any missing traces or vias
  • Watch out for any schematic errors
  • Keep an eye on the environment that the PCB has to operate in and plan accordingly
  • Ensure there is communication between the PCB designer and the electronics engineer
  • The designer needs to understand the fabrication process including aspects such as dimensional tolerances.

Last but not the least, ensure that there is robust test planning so that you do not have to deal with costs of rework and product recalls.


About the Author

Suresh Patel has worked as a sales engineer and other management roles at Mer-Mar Electronics. He brings 25 years of experience in printed circuit board sales and technical client service and managing business. You can connect with him on Twitter.


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