How to identify multilayer PCB?
PCB layers are the determining factor in the power and capacity of a printed circuit board. People often wonder whether a one-layer PCB will suffice, or if it is better to go with a two- or four-layer PCB - hint: there is no such thing as a three-layer PCB - or something in the multilayer range.
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While the numbers of layers largely depend on your budget and functional needs in a PCB board, this does lead to question - what exactly are multilayer PCBs? Basically, "multilayer" refers to anything with more than two layers, such as a 4-layer PCB or something in the 6-layer to 12-and-up range.
In the passage, we will tell you everything about the multilayer PCB and how to identify multilayer PCB. Come and check the content below and read for more professional knowledge.
What are the common questions to identify multilayer PCB?
As you consider how many layers would be ideal in an order of PCBs, you need to consider the factors that make a multilayer favorable to a single- or double-layer, and vice versa.
1. How will my printed circuit board be used?
When calculating the needs of a printed circuit board, consider the types of machines and devices your PCBs will be used in and the demands these machines/devices will place on the board circuitry. Will these PCBs be used in high-tech, complex electronics or in simpler items with minimal functions?
2. What operation frequency is needed?
As you take these questions into account, consider what you will need in terms of operation frequency. Its parameters determine the functions and capacity of a PCB. For higher speed and operating capacity, multilayer PCBs are essential.
3. What is my budget for the project?
Other things to consider are the manufacturing costs of single- and double-layer PCBs versus multilayers. If you want to have the highest capacity possible in today's circuit board technology, you will need to pay for the high manufacturing costs involved.
4. How quickly do I need the PCBs?
Lead time - the time it takes to manufacture a set of PCBs of single vs. multiple layers - is also something to consider when you order a large shipment of printed circuit boards. The lead time for one- and two-layer boards could be anywhere from 8 to 14 days, depending on the size of the board area. Then again, if you are willing to pay more or less, the lead time could be as short as five days or as long as a month. The lead time will increase, per board size, with every layer you add to the order. PCBs in the four- to 20-layer range could have a lead time of anywhere from 12 to 32 days, depending on whether you want the boards to have small or large dimensions.
5. What density and signal layers are needed?
The number of PCB layers also depends on pin density and signal layers. As indicated by below chart, a pin density of 1.0 will necessitate 2 signal layers, and the number of necessary layers goes up as the pin density drops. With a pin density of 0.2 or less, you will need PCBs with at least 10 layers.
For 2 layer PCB
The two-layer PCB is the next step up in printed circuit board technology. With its higher capacity, the two-layer PCB - alternately called a double-layer PCB - can support a wider range of contemporary electronics devices than the one-layer PCB. At the same time, two-layer PCBs are much less complicated from a manufacturing standpoint than the various multilevel printed circuit boards on today's market. As such, the two-layer is the most widely used PCB option.
A two-layer PCB is much like a one-layer PCB, but with an inverted, mirror-image bottom half. With the two-layer PCB, the dielectric layer is thicker than in the single-layer. Furthermore, the dielectric is laminated with copper on both the top and bottom sides. Moreover, the lamination is covered with soldermask on both the top and bottom.
Illustrations of the two-layer PCB generally look like a three-layer sandwich, with a thick grey layer in the middle that represents the dielectric, twin brown strips above and below that represent the copper and thin green strips along the top and bottom that represent the soldermask.
Thanks to its equal top and bottom sides, the two-layer PCB allows for more routing traces. The benefits of the two-layer PCB include the following:
• A flexibility of design that makes it suitable for a broad range of devices
• Dense circuitry that makes it suitable for a range of modern-day applications
• Low-cost construction, which makes it convenient for mass production
• Simple design, which makes it easier for manufactures around the world to understand
• Small size, which allows it to fit in a variety of devices
For 4 layer PCB
A four-layer board consists of a more complex set of layers than the one- or two-layer PCB. Whereas both the single- and double-layer PCB contain a single row of dielectric material, the four-layer PCB contains several. As with all multilevel printed circuit boards, the four-layer PCB includes several layers of conductive material and copper between the top and bottom soldermasks.
The four-layer PCB stackup consists of the following layers:
• Four strips of conductive copper
• Three inner-dielectric layers - two prepreg and one core
• Twin dielectric soldermask layers at the top and bottom
In 4-layer PCB design, the 4 copper strips are divided internally by 3 inner dielectrics and sealed at the top and bottom by soldermask. Generally, 4-layer PCB design rules are illustrated with 9 strips and 3 colors - brown for copper, gray for core and prepregs and green for soldermask.
Even though the common illustrations of four-layer PCB design would seem to indicate the prepreg and core layers consist of the same material, the former is not totally cured, and is therefore softer than the core. During the manufacturing process, heat and pressure are applied to the four-layer stackup that causes the prepreg and core to melt and bond the layers together.
For 6 layer PCB
The six-layer PCB is where circuit board technology really starts to get into the more advanced aspects of today's electronics. With the six-layer PCB, manufacturers can power a range of commercial tech products, health care devices and industrial machinery.
The six-layer PCB stackup is similar to the four-layer, but with two extra copper layers and two additional rows of dielectric material. In the six-layer stackup, the second and fourth dielectric rows are labeled as "core", and the first, third and fifth are prepreg. Of the six conductive copper rows, the second and fifth are plane and the rest are signal.
For complex multilayer PCB
As the multilayer printed circuit boards increase in layer count beyond the numbers four and six, further layers of conductive copper and dielectric material get added to the stackup.
For example, an eight-layer PCB contains four plane and four signal copper layers - eight in all - bonded by seven inner rows of dielectric material. The eight-layer stackup is sealed at the top and bottom with a dielectric soldermask. Basically, the eight-layer PCB stackup is much like the six-layer, but with additional pairs of copper and prepreg columns.
The trend continues with the 10-layer PCB, which adds two more layers of copper for a total of six signal and four plane copper layers - 10 in all. Bonding the copper in the 10-layer PCB stackup are nine columns of dielectric material - five prepreg and four core. Ten-layer PCB stacks are sealed, like all others, with dielectric soldermask at the top and bottom.
By the time you get to the 12-layer PCB stackup, you have a board with 4 plane and 8 signal conductive layers, bonded by 6 signal and 5 core columns of dielectric material. 12-layer PCB stacks are sealed with dielectric soldermask.
PCB Knowledge ⋅ 07/06/2021 17:06
