Why should multilayer pcb manufacturing have copper tracks?2021-08-07
What is a PCB or printed circuit boards and what type is there?
In this article you will know all the basics about multilayer pcb manufacturing, its number of layers and how to count it. Moreover, we shall read the types and subtypes according to their number of layers, standard manufacturing material and others.
In addition, you will also know all the terms common in this field, such as:
- what is a multilayer plat
- rigid-flexible layer
- which are the microvias and blind vias
Introduction to multilayer pcb manufacturing
Printed Circuit Boards are present in all electronic devices today, from computers, mobile phones or the mouse itself to washing machines. Before the appearance of these boards, all the devices had loose electronic components, full of cables, resistors and circuits distributed throughout the chassis.
On the other side of the substrate, if it has another layer, then another layer of conductive tracks will go, resulting in a sandwich. The more layers, the longer and more complex the multilayer pcb manufacturing process is. Furthermore, we also save the space in the devices, making them smaller and smaller.
Here we can see the cross section of a 4-layer copper PCB with FR-4 and RO4003C insulations of different thicknesses, and with a through hole. Moreover, we will also talk about these holes later.
Why should multilayer pcb manufacturing have copper tracks?
For a PCB to be usable by the user, it must have the copper tracks where the components will go. For them the manufacturing process is more complex, but in summary we can say the following.
Using the image below as a reference, the top layer is where the components would weld to the tracks. The application of soldermask on the copper layer is a process that carries out using sheets and ultraviolet light.
Similarly, it exposes certain areas to light, where we remove the unexposed areas during chemical development. In addition, the remaining solder mask we fully cure to a stretchy finish.
The placement of connectors and ports on multilayer pcb
Next, and after various finishes, a legend or silkscreen is printed that will contain the information that the designer wanted to appear on the PCB. Usually the name of connectors, codes of elements and ports, brand, etc. we add during multilayer pcb manufacturing.
PCBs can be classified by their type of laminate, their construction, their electrical characteristics, and their structure. As we have discussed above, PCBs can therefore be classified according to the number of layers:
- Unilateral / bilateral
- Multilayer (up to 28 layers)
- Moreover, HDI multilayer
HDI multilayer pcb manufacturing
HDI (High Density Interconnect) multilayer boards have laser drilling of microholes and a density of tracks per unit area much higher than those of conventional PCBs. Moreover, it comes according to the IPC-2226 standard that defines them.
They have lines and spaces between them than those common in conventional PCB technology.
3 types of HDi PCB Board structure
Within the HDI multilayer PCBs there are 3 types according to their main structure according to the use of microvias, blind or buried routes. We shall explain this later, as indicated by the IPC regulations.
Type I: This multilayer pcb manufacturing defines a single micro-path layer on one or both sides of the nucleus. It uses both metallized microvias and metallized drills for interconnection, using blind, but not buried, vias.
Type II: Generally, it defines a single micro-path layer on one or both sides of the nucleus. It uses both metallized microvias and metallized drills for interconnection. Blind and buried routes are common.
Type III: It defines at least two layers of microvia on one or both sides of the nucleus. It uses both metallized microvias and metallized drills for interconnection, uses blind and buried vias.
Construction terminology to define the HDI construction grade:
- a single micro-path layer
- 2 micro-path layers
- Moreover, 3 layers of micro-path
– What is a microvia?
According to the new definition of the multilayer pcb manufacturing, a microvia is a blind structure with a maximum aspect ratio of 1: 1, ending at a point with a total depth of no more than 0.25 mm measured from the layer of starting copper up to the target layer.
What is a blind road?
It is a path that runs from an outer layer to an inner one, and therefore does not cross the entire PCB. These pathways can be performed mechanically or using laser technology.
What does it mean that a road is buried?
It is a path that crosses one or more of the inner layers, and therefore does not go outside. They are usually made with a mechanical drill.
Double sided flexible multilayer pcb manufacturing
Flexible multilayer Coating bonded on both sides of a structure without adhesive that contains three or more conductive layers with metallized holes. With or without reinforcement. The capacity is 4L in multilayer pcb manufacturing.
Traditional rigid-flexible structure Combination of rigid and flexible multilayer circuits containing three or more layers with metallized holes. Furthermore, it comes with22L capacity with 10L flexible layers.
Asymmetric rigid-flexible structure, in which the FPC is located in the outer layer of the rigid structure. Contains three or more layers with metallic holes.
– Rigid-flexible multilayer structure with buried / blind roads (microvías) as part of the rigid structure. 2 layers of microvias can be achieved. The structure can also include two rigid structures as part of a homogeneous construction. The capacity is a HDI 2 + n + 2 structure.
Book-binder and air-gap structure – a complex structure the spaces between the flexible layers allow a better bending of the flexible multilayer pcb manufacturing. The flex layers can be of different lengths in book-binder constructions to minimize compression of the inner flex layers at the bend radius.
PCB on an aluminum core
The most common type of all metal core PCBs are aluminum printed circuits (IMS – insulated Metal substrates). The base material consists of an aluminum core and standard FR4. It features a thermal coating layer that dissipates heat in a highly efficient manner while cooling components and increasing the overall performance of the products.
Why aluminum multilayer pcb manufacturing?
Today, aluminum-backed PCB is considered the solution for high-power, tight-tolerance applications. The main fields of application are in the fields of lighting:
- Generally, high-power LEDs
- street lamps
in automotive fields:
- Moreover, control units
- inverter switching
- Similarly, voltage regulators
- Moreover, output amplifier
- balanced amplifier
- Similarly, audio amplifier
- In addition,power amplifier; and in power supplies: switching regulator, DC / AC converter, SW regulator, etc.
Advantage of aluminum multilayer pcb manufacturing:
Aluminum multilayer pcb manufacturing is environmentally friendly: aluminum is non-toxic and recyclable. The aluminum construction also favors energy conservation due to its ease of assembly. For suppliers of printed circuit boards, the use of this metal helps to maintain the health of our planet.