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