< img height="1" width="1" style="display:none" src="https://www.facebook.com/tr?id=1724791474554128&ev=PageView&noscript=1" />

2 Layer PCB: The Ultimate FAQ Guide

Before you invest in a new 2-layer PCB, you should read this guide.

It has all information you’re looking for about multi-layer printed circuit boards.

So, if you want to be an expert, keep reading.

What is a 2 Layer PCB?

A 2 layer PCB is a printed circuit board with two layers of conductive copper traces.

These layers are referred to as the top and bottom layers.

It is also known as a double-sided PCB and it allows a higher component density than the single-sided PCB.

You find the 2 layer PCBs used in various electronic circuit applications in the electronic industry.

2 layer PCBs can be used for simple circuits as well as sophisticated circuitry formations.

Some common circuits utilizing 2 layer printed circuit boards include circuits for automotive application, cellular devices, and equipment for testing, monitoring and instrumentation.

2 Layer PCB
2 Layer PCB

How is a 2 Layer PCB Constructed?

You find a 2 layer PCB made from the lamination process where two copper foils are used to sandwich a substrate.

Fiberglass is commonly employed as a substrate for printed circuit board construction.

How are Components Connected to a 2 Layer PCB?

You find two methods typically used in connecting components to the 2 layer PCB, that is, through-hole mounting and surface mounting.

In through-hole connection, components have leads that are inserted into drilled holes to secure them to the board.

Surface-mounted components are soldered to the board surface.

Surface mounting has the following advantages:

  • SMT allows the compact arrangement of components allowing for smaller boards that can be used in miniature devices.
  • You find that SMT requires no holes reducing costs incurred in drilling.
  • The process of attaching components in surface mounting is faster than that of through-hole mounting.
  • 2 layer boards with SMT are highly compact allowing faster performance.
  • You find surface mounted components can be accommodated on both the top and bottom layers allowing for increased density.
  • SMT reduces induction eliminating the adverse effects of radiofrequency interference.

However, you find the SMT is limited in the following ways:

  • The tight fit of surface mounted components repairs a difficult process. Furthermore, soldering provides a permanent joint which discourages replacements.
  • The thermal cycling process used in the soldering process can damage connections.
  • SMT cannot be used for components with large heat dissipations as they would break the solder joint through melting.
  • You find surface mounted components are susceptible to rough handling and physical stress conditions.

On the other hand, you find the following benefits attached to through-hole mounting:

  • Through-hole mounting is reliable as it provides a firmer board connection for components.
  • You find through-hole mounted components can sustain large stress conditions without the danger of breaking the board connection.

However, setbacks related to through-hole mounting include:

  • The holes required for through-hole mounting are drilled adding to the overall board cost and time.
  • Routing is limited in a through-hole board configuration, especially where there are multiple layers.
  • The time taken to place components on the board using through-hole mounting is longer than SMT.
  • The soldering techniques for through-hole mounting require operations on both sides and cannot support repeatability.

Can a Board be 2 Layers with Components on One Side Only?

Yes, it can.

A board can be 2 layers with components on only one board side if conductive traces are on the other side.

It is not the presence of components on both board sides that makes a printed circuit board a 2 layer PCB.

It is rather the presence of conductive traces derived from a layer of copper foil.

Are Arrays used in the Fabrication of 2 Layer PCB?

Yes, they are.

Arrays are useful in the fabrication of large scale orders of 2 layer PCBs allowing for automation and repeatability.

There are two common alternatives for arrays which can be used separately or combined: scoring and tab routing.

A combination of arrays serves complex designs with undefined margins.

Scoring as an array is used for 2 layer board designs with uniform edges.

This technique is characterized by reduced material wastage and thus material savings in cost.

Layers of panels are stacked together in bundles to be scored.

You find that material savings are more pronounced on large productions.

Tab routing applies to 2 layer board designs with non-standardized shapes.

Furthermore, you use tab routing array when components are to be positioned along the periphery of the board.

In this array, an allowance of less than a quarter of an inch is provided between boards.

Tab routing is supported by the use of rails to aid in assembly.

What Material is Used for the Base of a 2 Layer PCB?

The non-conductive material is used for the 2 layer PCB base.

It is called a substrate and is commonly made from fiberglass reinforced with epoxy resin.

You can alter the substrate material to make your board flexible or rigid.

2 layer printed circuit board
2 layer printed circuit board

Is a Solder Mask used for the 2 Layer PCB?


A solder mask offers protection for the copper path of both layers during the soldering process from oxidation.

Moreover, since solder is conductive, when allowed to interact with the copper traces, it can create undesired paths for electrical conductivity.

Some of the materials used in making solder masks include epoxy liquid which is least expensive and laid through screen printing.

The liquid photo-imaginable ink is being applied by screen printing or spraying.

The dry-film photo-imagable solder mask which is applied via a vacuum process of lamination.

How do you Solder 2 Layer PCBs

Unlike a single-sided board where the soldering process might be less complicated, soldering two layers of a PCB poses a great difficulty.

This is especially true when carried out manually.

However, you can greatly simplify the soldering process of a 2 layer PCB by:

  • Using a pick and place contraption
  • Using a computer numerical controlled milling machine

Soldering involves the use of solder flux and paste.

Solder flux serves the purpose of purifying components ridding them of unwanted particles such as rust.

Furthermore, it reduces the chance of rust to reoccur by locking air out during the soldering process alongside enhancing the solder drip.

Soldering paste is used to attach the components to the board.

What are the Advantages of the 2 Layer PCB?

You find the 2 layer PCB with the following attractive traits that make it preferred for many PCB designs:

  • You can achieve a higher component density with the 2 layer PCB
  • A 2 layer PCB allows for the copper traces to be routed closer than a single-sided PCB.
  • The 2 layer PCB can find simplified and varied use across different circuit demands.
  • Compared with other multilayer printed circuit boards, the 2 layer PCB is cheaper.
  • You find the 2 layer PCB offers more circuit density compared to the single-sided board.
  • With a 2 layer PCB, you can make smaller boards with a high component count than a single-sided board.
  • The configuration of a 2 layer board allows multiple usages such as using the bottom layer as a copper pour or ground plane.
  • You can also use a 2 layer PCB as a current source in an electrical system.
  • There is better component management with a 2 layer PCB as components can be organized over both surfaces. You can have through-hole components on the top layer and surface-mounted components on the bottom layer.
  • A 2 layer PCB can be used to accommodate grounding and the common collector voltage via the bottom layer. Using this approach allows the size of the board to remain unchanged.

Are Vias used in 2 Layer PCBs?

Vias have drilled holes that are plated with conductive material to allow for electrical transfer between multiple layers.

There are three types of vias: the blind vias, the through vias, and the buried vias.

The blind and buried vias are associated with inner layers which a 2 layer PCB lacks.

As such, only through vias are used in 2 layer PCBs.

Through vias offer an electrical connection between the top and bottom layers.

What Copper Weights are used for the 2 Layer PCB?

The weight of copper in a PCB is provided in ounces (oz) and taken over a spread of a square foot.

The copper weight helps in determining the thickness of the conductive trace.

Besides, the 2 layer PCB commonly employs copper weights of half an oz, a single oz, or 2 oz for its layers.

You will find a 1 oz copper PCB in a two-layer formation with each layer amounting to half an oz.

1 oz copper pcb
1 Oz copper PCB

Similarly, a 2 oz copper PCB will have two layers of a single ounce of copper each.

2 Oz copper PCB
2 Oz copper PCB

Can a 4 Oz Copper PCB be made in a 2 Layer PCB Formation?


4 oz copper PCB can be made in a 2 layer PCB configuration.

4 Oz Copper PCB
4 Oz copper pcb

You find it possible through the use of layers made of 2 oz copper each.

The construction is such that a core of the substrate is made and laminated with two copper films of 2 oz weight.

What Holes are Drilled on a 2 Layer PCB?

There are two types of holes drilled on a 2 layer PCB.

You find plated holes and non-plated holes.

Plated holes are made close to the board edges.

They are lined with a conductive material such as copper to allow for thermal and electrical transfer.

Non-plated holes are plain walled holes with no conductive capabilities.

These holes are usually kept apart at no less than half a millimeter apart with hole diameters of 0.5 mm.

To make the holes, a CNC machine with a drill bit is used.

The whole arrangement and pattern are dependent on the PCB design.

The plating of the hole extends outside the hole to form a flat base at the entry and exit points.

How are the Traces on 2 Layer PCBs Determined?

The traces on 2 layer PCBs are used as the conductive path for electric charge transfer.

The conductive trace parameters of trace width and trace spacing are determined by the copper weight of the layer.

Furthermore, you find the current requirements and component density useful in establishing the trace parameters.

What is Impedance Control concerning a 2 Layer PCB?

Impedance refers to the collective value of reactance, resistance, and conductance exhibited by a circuit in a 2 layer PCB.

Impedance control seeks to minimize the effects of impedance during board operation.

Also, impedance is affected by the conductive path length and dielectric properties of the core.

Besides, impedance values affect the operation of 2 layer PCBs used in high power and high-speed applications.

Impedance effects are demonstrated by an increase in signal deflection and distortion.

If left unchecked impedance can jeopardize radio frequency transmission.

Impedance control minimizes signal deflection while mitigating signal distortion by considering impedance values at the design stage.

You can identify materials with properties less vulnerable to impedance encroachment.

Also, the layer arrangement needs to be considered since chances of impedance increase with increasing layer count.

What Routing Methods can be used for the 2 Layer PCB?

Routing provides the addition of wires on a PCB for proper component connection.

Individual routing of the board can be carried out for single board projects.

For multiple boards, palletization and V-score routing can be carried out.

These boards are arranged in an array and more common for an automated assembly process.

How is Silkscreen Applied on the 2 Layer PCB?

The silkscreen is an informative sheet placed over the solder mask.

It provides information related to the board, and components used, through the use of characterizations and symbols.

Some of the information includes points of test, part numbers, manufacturer’s information, and identifiers for components.

You find two common methods of applying silkscreen onto a 2 layer PCB.

Silkscreen can be applied through screen printing where the desired information is printed over a stencil.

An ink-jet printer can also be used to print a silkscreen via digitized information.

Why are Tolerances Important in 2 Layer PCBs?

2 layer printed circuit board
2 layer printed circuit board

Tolerance is an allowance for dimensions related to the 2 layer PCB such as hole and pad sizes.

Tolerance is useful as it provides flexibility in your design while adhering to the ethos of designing for manufacturability.

What Surface Finish is used for the 2 Layer PCB?

There are several finishes available for the 2 layer PCB.

Some common finishes include:

  • Immersion silver, which offers a smooth surface while providing good solderability. However, you find this finish limited in terms of its ability to handle environmental factors such as temperature and humidity.
  • Hot Air Solder Level which has a longer shelf life and strong solder joint. A smooth finish is difficult to achieve with this finish type and thus less favorable for use with fine finish demands.
  • Electroless Nickel/Immersion Gold is favored for its smooth surface, strong joint on soldering, and resistance to environmental factors such as temperature and humidity. ENIG is also highly flexible in finding use in different designs.

What are Gold Fingers on a 2 Layer PCB?

Gold finger PCB
Gold finger PCB

Gold fingers are used to denote the connector edge terminations used for insertion for a 2 layer PCB.

Gold fingers are made from gold hardened to offer a smooth finish with high wear resistance even with recurrent use.

Gold fingers can be used alongside other types of surface finishes enhancing solderability and protection from wear.

What Quality Testing Method is used for the 2 Layer PCB?

Testing of a 2 layer PCB helps to establish the conformity of the 2 layer PCB to the design needs.

It also evaluates its reliability across the two-layer formation.

An electrical test can be carried out on the 2 layer PCB without components and when it is populated.

You find the electrical test useful in establishing shorts and opens on the top and bottom layer of the PCB.

With this test, a flying probe is used to identify points of electrical isolation and undesired connections.

Faults are corrected and tested again before the assembly of components is carried out on the board.

Identifying faults before assembly minimizes board failure.

If ignored, the cost to deal with an error especially after populating the board can be great.

A 2 layer PCB can also be tested when components have been attached to unearth failings related to the assembly process.

With this test, you can determine the functional failings of the board and those of connected components.

What are the Quality Standards for a 2 Layer PCB?

The following consist some of the standards provided for 2 layer PCBs:

· BS-123200-003

This standard provides for the quality assessment of a rigid 2 layer PCB with plated-through holes.

· BS-EN-61249-2-2

In this standard, materials for a 2 layer PCB and its interconnecting structures are provided.

· BS-CECC-23100-801

The standard is a harmonized system for assessing the quality of electronic components used on 2 layer PCBs with non-plated holes.

· BS-6221-4

The standard provides for a specification methodology for 2 layer PCBs with non-plated holes.

· BS-IEC-61189-5-3

This standard provides a generalized test procedure for electrical material and interconnections used on a 2 layer PCB.

It also provides guidelines for the solder paste use on the PCB.

· DD-IEC/PAS-62326-7-1

This standard is specific to the performance of both single and 2 layer PCBs.

As you can see, there are many factors you should consider when buying 2-layer PCB.

For standard and custom designs of 2 layer PCBs, Venture is always here to help.

Recent Posts
Contact Us
Send A Message