Everything you should know about multilayer PCB
PCBs or Printed Circuit Boards are the core component of electronic and electrical devices in the current time. Printed circuit boards are the essential part of devices having purpose of determining different functionalities combining numerous wiring mechanisms and components on to a single board achieving a specific goal. In the past, printed circuit boards used to be very simple in design and appearance and a couple of techniques were being used for its manufacturing.
However, now the manufacturing techniques have become complex and so is the appearance achieving sophisticated goals. The multilayer PCB is a type of PCB having many layers, usually more than three interconnected together for acquiring a specific function.
What is a multilayer PCB?
For fabricating a multilayer PCB, numerous layers are required to be interconnected. However, multilayer PCB is not the same like double layer PCB that has only layers for conduction of current. Instead, multilayer PCBs have more than two paths for conduction. The conductive layers are supposed to be buried within the center of the material.
What is a multilayer PCB made of?
In order to fabricate the multilayer PCB, numerous layers of core material and pre-peg are to be laminated considering high pressure and temperature. The process is for ensuring that air is not trapped among the layers. The conductors of the PCB are entirely encapsulated through resin and the adhesive is holding the various layers intact. The material range of multilayer PCB is very vast starting from basic epoxy glass to Teflon and other ceramic materials. The material for the core and pre-peg is often the same.
However, pre-peg is not entirely cured which makes it valuable when compared to core. Moreover, the alternating layers of the PCB are placed within a lamination press after which high pressure and temperature are applied to stack them up that cause the pre-peg to melt and intact the layers together. This is how a hard and solid multilayer PCB board is fabricated.
Why is multilayer PCB needed?
Industry trends have made the multilayer PCB frequent to be used in the manufacturing of electronic devices. With the progress made towards the miniaturization and multifunctionality of electronic devices, their internal components are supposed to follow the same trend.
Furthermore, double and single sided PCB are found to have limited capabilities and functioning; therefore, multilayer PCBs offer a thorough solution. It is a fact that multilayer PCBs have only a few drawbacks but having advanced performance and reliability.
Therefore, the functionality of multilayer PCB is having an edge over its cost and is used in electronic devices. Furthermore, with the advancements in technology the machinery is upgraded along with techniques of production making the multilayer PCB affordable. Therefore, with such irreversible trends and continued progress in technological advancement, multilayer PCB is expected to see increased growth in the manufacturing of electronic devices.
What is the difference between single-layer and multilayer PCBs?
|Single layer PCB||Multilayer PCB|
|A single layer of the base material is used in the single-layer PCB.||Multilayer PCB has more than two layers.|
|The base material is also known as the substrate and has a single layer.||The multilayer PCB is having many layers of substrate.|
|These have one conductive metal layer.||These have more than two conductive layers.|
|These have one protective solder mask.||These have more than two protective solder masks.|
|One layer of silk-screen is there.||More than two layers of silk-screen are there.|
|These PCBs have lower costs.||These PCBs are expensive.|
|Single-layer PCBs have high volume.||These are light in weight.|
|These have shorter lead time.||These have higher lead time.|
|These have simple design.||These have complex design.|
|The speed of operation is very slow.||The speed of operation is very high.|
|The quality is low.||The quality is high.|
|These are readily available.||The availability is difficult.|
How is multilayer PCB connected?
The multilayer PCB is having more than two layers of conducting material. These layers appear in the form of various layers of double-sided circuits that are laminated and glued together. The arrangement of layers is made in such a way that the layers are placed on the surface for having a connection with the environment. The electrical connection through the middle of layers is acquired through vias. The vias can either be buried or blind type that are plated through holes.
Where are multilayer PCBs used?
Multilayer PCBs are widely adapted throughout the different sections of electrical and electronic industries. There are various advantages of multilayer PCB apart from being exceptional in performance such as low weight and compact size etc. The following are some common uses of multilayer PCBs.
- Laptops and computers
- Data storage devices
- Signals reception and transmission devices
- Cellphones and tablets
- GPS devices
- Satellite systems
- Control circuits of industries
- Aerospace industry
- Biomedical industry
- Military industry
- Safety devices such as fire alarms
- Weather analysis devices
- Nuclear detection devices
How to create a multi-layer PCB?
The process of creating a multilayer PCB is not that simple. However, with the advancement in technology and utilization of state-of-the-art techniques, it has become more prevalent. Following is the process of creating a multilayer PCB.
- The first step is the creation of a layout design through PCB layout software like EagleCAD, Proteus, PSpice, etc.
- The second step is the creation of the core layer or inner layer. Copper foil is utilized for the lamination of the desired thickness of the core layer.
- Lamination is the third step comprising the sheets of copper foil, pre-peg, and inner layers. These sheets are stacked over each other and then holes are utilized for the alignment of the stacked sheets. For instance, for a multilayer PCB having four layers, the stacking process will be like at the bottom there is going to be a copper foil layer, a pre-peg sheet, an inner core layer, and then another pre-peg sheet. At the top copper foil is placed.
- Application of high pressure and temperature under vacuum is the next step to be followed. The vacuum creation is of great importance to ensure no air traps among the layers.
- Afterward, the resins of the pre-pegs are joining the sheets, copper foil, and core together resulting in the formation of a multilayer PCB.
What are the considerations in multilayer PCB design?
The following considerations should be made while designing multilayer PCBs.
- The layer of route adjacent signal must be in the opposing direction over the PCB. If the adjacent signal layer is over the 2nd and 3rd layers, then the route must be made in the horizontal direction for one and in the vertical direction for the other. This helps in avoiding crosstalk problems.
- The utilization of plane and power layers must be made. This will not only assist in the even distribution of ground and power but is also creating a microstrip structure helping in the integrity of signals.
- The size of the inner signal layer must be reduced with thru-hole pads.
It can be concluded that multilayer PCBs are sophisticated and fabricated under state-of-the-art technology and manufacturing processes. The use of such PCBs is not limited to a specific industry or application but are widely adapted in almost every industry because of its high performance and features.