Advanced Multilayer PCB Manufacturing Services

What is a multilayer PCB

A multilayer PCB is a printed circuit board used in electrical products that has more than one layer of wiring. A multilayer board uses extra một lớp or double-layer boards stacked together. For example, a board that uses one double-sided board as an inner layer and two single-sided boards as outer layers, or two double-sided boards as inner layers and two single-sided boards as outer layers, becomes a four-layer or six-layer printed circuit board. These boards are made by stacking and bonding with insulating bonding material and by using alignment systems. The conductive patterns are connected as the design needs. These boards are also called multilayer printed circuit boards.

Multilayer PCB design: how to decide the number of layers

The performance and cost of a printed circuit board depend a lot on how many layers it has. So it is important to choose the number of layers correctly. This article focuses on the main points to think about when you design PCBs from 1 to 20 layers.

Important factors to consider when choosing 1–20 layers

Let us start with the things to think about. Maybe you know roughly how many layers your PCB needs. But you should check why a multilayer PCB may be better than a single-layer PCB. Look at the points below to clear your doubts:

• Use or application: Where will the PCB be used? As said above, PCBs are used in many types of simple and complex electronic devices. So you must know if your application needs minimal function or complex function. A simple device may do fine with one layer. A complex device often needs more layers.

• Type of signals needed: Do the boards need to carry microwave or high-frequency signals? The layer choice also depends on the types of signals they must carry. Signals can be high frequency, low frequency, ground, or power. If your application needs many different signal paths or mixed signals, you will need a multilayer PCB. These circuits may also need separate ground and shielding layers.

• Via types: The type of vias you choose is another key factor. If you choose buried vias or blind vias, you may need more internal layers. So via choice can change the number of layers you need.

• Density and number of signal layers needed: The layer decision also depends on two important things: signal layers and pin density. The number of layers in the PCB tends to grow as pin density goes up. For example, if pin density is 1.0, you may need 2 signal layers. But if pin density is less than 0.2, you may need 10 layers or more.

• Number of planes needed: Power and ground planes help lower EMI and shield signal layers. So the number of planes you need will affect the layer choice. More planes mean more layers.

• Manufacturing cost: Though it is not the only need, cost is a key factor in choosing layers for a 1–20 layer PCB design. The cost to make the PCB rises with more layers. Multilayer PCBs are more expensive than single-layer boards. The cost will depend a lot on the requirements listed above.

• Delivery time: The lead time for a 1–20 layer PCB order depends on all the factors above. For example, if your design only needs a single layer, the lead time may be short. If you order boards for complex industrial electronic devices, the delivery time will be longer.

If you cannot decide based on the points above, you can discuss your needs with the PCB manufacturer Philifast.

What are the pros and cons of multilayer PCBs

Compared to single-sided PCBs, multilayer PCBs show clear differences in their surface and in their life performance. These differences are key to the board’s durability and function. The main advantages of multilayer PCBs include resistance to oxidation, varied structure, high density, and the use of surface coating techniques that ensure board quality and safety. Below are important high-reliability features and the pros and cons of multilayer PCBs:

1. Hole wall copper thickness is normally 25 microns

• Advantage: Increased reliability, including better resistance to z-axis expansion. The thicker copper on the hole wall helps strength and life.

• Risk: There are some risks. In real use, issues like blow-out or outgassing, or problems in the assembly process, may affect electrical connections. These issues can cause inner layer separation or hole wall cracking. Under load, these faults can lead to failure. IPC Class 2 (which is the standard for many factories) may require that copper plating on multilayer boards be less than 20% [note: this sentence keeps the original numeric reference].

  (Keep in mind: the exact IPC rule details depend on the rule set and factory practice. The point here is that hole plating and its control matter to reliability.)

2. No solder repair or open-circuit repair

• Advantage: A perfect circuit boosts reliability and safety. No need for maintenance in normal use.

• Risk: If repair is poor, the multilayer PCB can become open. Even when fixed correctly, under load conditions such as vibration, there may still be a risk of failure. This can lead to field failures.

3. Cleanliness standards beyond IPC norms

• Advantage: Higher cleanliness on a multilayer PCB improves reliability.

• Risk: Residues on the board and solder buildup can harm the solder mask. Ionic residues can cause corrosion and contamination on soldering surfaces. This can cause reliability problems like poor solder joints or electrical faults and, in the end, increase the chance of real failures.

4. Strict control of shelf life for each surface finish

• Advantage: Good control of surface finish helps soldering, reliability, and lowers the risk of moisture ingress.

• Risk: Old surface finishes on older multilayer boards may show metallurgical changes. They may cause solderability problems. Moisture ingress may cause issues during assembly or later delamination in the field. This can lead to inner wall separation and open circuits.

No matter if in the manufacturing and assembly lines or in real use, multilayer PCBs must show reliable performance. Of course, this reliability links strongly to the maker’s equipment and process skill level.

Differences between single-layer and multilayer PCB prototyping

When you design and build a printed circuit board, you must decide if a single-layer or multilayer PCB fits your device. Both types are used in many standard uses. But the needed type depends on what you use the board for. Each type has specific features that make it fit certain tasks. Simple home devices often use single-layer boards. More complex machines need multilayer PCB designs.

Single-layer PCB

A single-layer or single-sided board includes a base layer, one conductive metal layer, and a protective solder mask and silkscreen. Most manufacturing processes use copper as the conductive metal. One side of the board holds all the needed components. The other side has the conductor pattern.

Because their design is simpler than double-sided and multilayer boards, single-layer PCBs are cheaper and easier to make. This simple design is also their main shortcoming. They have fewer connection points. So single-layer PCBs have lower speed and fewer options for routing complex circuits.

Double-sided PCB

Another option is a double-sided PCB. It has more layers than a single-layer board, but fewer than a multilayer board. Like the single-sided variety, a double-sided board uses one substrate layer. The main difference is that the double-sided board has a conductive metal layer on both sides of the substrate.

Double-sided boards let you route more signals than single-sided ones. They still cost less than multilayer boards. They are a good middle choice for many designs.

Bo mạch in nhiều lớp

A multilayer PCB consists of three or more double-sided boards that are bonded together with special adhesive. Each board has insulating material between layers. Although a multilayer board can use many stacked boards, most have an even number of layers, often between 4 and 12. This is because an odd number of layers can cause warpage and twist after soldering.

With more boards and more connections, multilayer PCBs fit devices that need many functions and advanced features. They have higher operating ability and faster signal performance than single- or double-sided boards. But their design is more complex, they cost more, lead time is longer, and they need more care in repair and assembly.

Final notes

Choosing the right PCB type depends on your product needs, signal types, pin density, plane needs, cost limits, and delivery time. Talk with your manufacturer early if you are unsure. A good PCB maker can help you trade off cost, performance, and lead time. If you want help with layer counts and stackup for a specific product, you can discuss the design with Philifast or another qualified PCB manufacturer.