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Mixed Copper PCB: The Ultimate FAQ Guide

Table of Contents

Probably, you have any questions about mixed copper PCB.

A reason this guide explores everything you need to know about mixed copper PCB – from features, material type, applications to surface finish options, just to mention a few.

Keep reading to learn more.

Why Will You Use Copper In Mixed Copper PCB?

Mixed copper PCBs find their application in several electronic devices, and ensure they remain functional.

This makes them an important part of electronic devices since they are also durable and compact and ensure proper signal transfer.

Mixed copper PCBs contain several layers but one vital element you use when fabricating these boards is copper.

mixed copper PCB

Mixed copper PCB

Here are some reasons why copper is suitable when making mixed copper PCBs:

Suitable Conductor

Copper material is a good conductor of electricity and heat thereby improving the transfer of heat within the mixed copper PCB.

Otherwise, such stress can cause micro-fracturing thus resulting in the board failing.

The suitable electrical conductivity will enhance signal transmission without any loss in electricity.


Mixed copper PCB manufacturers need to use a small amount of copper as it is a suitable conductor.

This means that you can use a small quantity of copper and achieve the desired result.

Thermal Resistance

Copper has a suitable thermal resistance and current-carrying capabilities thereby enhancing the reliability of electronics.

Besides, this resistance makes it functional even in harsh weather situations such as high temperatures.

This will also enhance plated thru-hole and contact point’s mechanical resistance.

Heat Transfer

Since copper is efficient at transferring heat, you can directly install heat sinks on the surface of mixed copper PCBs.

Also, you can construct one part with heat-producing power parts and the other side with copper which will act as heat sinks.

Both scenarios allow you to lower the assembly of electronic devices, and in turn, lower the fabrication prices.

What Are The Types Of Mixed Copper PCB?

The examples of mixed copper PCBs present in the market today include the following:

Single-sided Mixed Copper PCB

This version contains one substrate layer and the mixed copper will shield one face of the substrate.

Single-sided mixed copper PCB has one side containing the electrical parts and the other side has the circuitry.

Furthermore, single-sided mixed copper PCBs are cost-effective for all types of mixed copper PCBs.

single sided mixed copper PCB

Single-sided mixed copper PCB

Double-sided Mixed Copper PCB

This version has two substrate layers, unlike single-sided mixed copper PCB.

These two substrate layers have conductive coats of metal layers with the components attached to both sides.

Besides, double-sided mixed copper PCB is used more than single-sided mixed copper PCB.

Holes within double-sided mixed copper PCB operate by connecting one side of the board to the other.

Furthermore, you can use either surface-mount technology or thru-hole technology to perform this task.

single sided mixed copper PCB

Double-sided mixed copper PCB

Surface-mount technology allows you to attach components directly to the surface of the mixed copper PCB.

This type uses no wires and saves space.

Thru-hole technology entails using wires to connect components on the board after passing them via pre-drilled holes.

Multilayer Mixed Copper PCB

This is a version of mixed copper PCB that contains 3 or more layers in its construction.

Besides, they will perform more operations as opposed to the double-sided mixed copper PCB.

Multilayer mixed copper PCB has several substrate materials which are separated with insulating substances.

In terms of available space that you can save, multilayer mixed copper PCB can save more space than double-sided mixed copper PCB.

Multilayer mixed copper PCB

Multilayer mixed  copper PCB

It is possible to find multilayer mixed copper PCB with 10 or more layers.

Rigid Mixed Copper PCB

This form of mixed copper PCB cannot bend or fold as it has a rigid structure.

The material that you will use when fabricating this PCB is fiberglass.

Rigid mixed copper PCB

Rigid mixed copper PCB

Flexible Mixed Copper PCB

The substrate material you will use in this version of mixed copper PCB is flexible.

This means you can bend or fold this board allowing it to fit in various places within electronic devices.

flexible mixed copper PCB

Flexible Mixed Copper PCB

Besides, they have several benefits over the rigid mixed copper PCB and will cost less.

Rigid-flex Mixed Copper PCB

This version contains both the characteristics of a rigid and flexible mixed copper PCB.

Besides, with this version, you can mount the rigid part of the board to the flexible portion.

rigid flex mixed copper PCB

Rigid flex Mixed Copper PCB

This feature proves to be challenging with other types of mixed copper PCBs.

Which Copper Is Suitable For Use When Making Mixed Copper PCB?

Signals will travel via the copper pathways within a mixed copper PCB.

Furthermore, other design factors are important when it comes to relaying these signals.

For this reason, it is important not to overlook any of these elements.

One important element is the quality and the type of copper you will use and how it will adhere to the dielectric layer of the PCB.

There are two types of copper foils that you will use when manufacturing mixed copper PCBs.

These are electrodeposited copper [ED] and rolled-annealed [RA] copper.

The fabrication of rolled-annealed copper begins by passing ingots of pure copper via several rolling methods.

This will produce a suitable copper foil thickness for your application.

When fabricating electrodeposited copper, you will plate copper within a drum.

The rotational speed of these drums will determine the thickness of the copper foil.

This means it will take much time when you prefer to make thicker copper foils.

The side contacting the drum is smooth while the opposite side is rough.

Besides, the etching process happens differently since both of these copper have varying grain structures.

Here are some other comparison features of these two types of copper:


Electrodeposited copper has a red appearance while rolled annealed copper has a yellowish appearance.

Surface Roughness

The surface that faces the solution of electrodeposited copper is rougher.

However, both surfaces of rolled annealed copper are almost equal and are much smoother than that of electrodeposited copper.


Electrodeposited copper is very robust mechanically.

Besides, ED copper may experience thermal stress cracks within narrower conductors due to a faster thermal cycling process.

Furthermore, ED copper exhibits a higher tensile strength and elongation before it begins to break.

Also, as the roughness of ED copper increases, there will be an increase in conductor loss, thereby negatively affecting insertion loss.

However, with rolled annealed copper, it will exhibit higher resistance to cracking conductors originating from thermal stress.

This proves to be paramount in areas where thermal shock is a concern.

Besides, RA copper has a better elastic elongation before it reaches permanent deformation.

It will also enhance the definition of etches in high-frequency and fine circuits.


Electrodeposited copper is suitable for use in areas where mechanical stress is an important factor.

Rolled annealed copper is suitable for high-frequency usage.

How Will You Design A Mixed Copper PCB?

In this modern age, there are various design approaches when dealing with mixed copper PCBs.

This means a manufacturer may decide to use a method that another manufacturer may fail to use.

Here are some important stages you will use when designing mixed copper PCBs:

Using A Software

This entails using design software to make schematics of the mixed copper PCB.

There are different types of design software out there for you to use, and some of them include eagle, CAD, etc.

Generating Film

After finalizing the mixed copper PCB layout design, you will generate the film.

Selecting Raw Materials

Affordable mixed copper PCBs use paper phenolic which you will bond with copper foil for use in simple electronic devices.

Besides, the thickness of copper-clad laminate has a value of roughly 0.059 with double-sided or single-sided PCB.

Drilling Holes

This entails using drill bits and a machine to make holes on the mixed copper PCB.

Besides, you can use either a hand machine or a CNC machine.

Hand machines are manual while CNC machines are automatic and will perform the task once you set the correct drilling parameters.

Fixing Images

One of the best ways you can use when printing layouts on the mixed copper PCB is using laser printers.

The steps you will conduct here entail:

  1. Placing a layer of clean copper on printers
  2. Storing the design layout film on the computer
  3. Using the laser printer to make the prints from the design

Etching And Stripping

Here, you will use various chemical substances to remove surplus or unwanted copper from the mixed copper PCB.


After completing the above stages, you need to test the functionality of the mixed copper PCB.

There are different ways to conduct these tests, such as automated optical inspection, X-ray inspection, etc.

How Can You Ensure You Achieve Proper Copper Balance When Designing Mixed Copper PCB?

When conducting design stack-up, it is recommended to place the center layer with the maximum thickness of copper.

Thereafter, continue balancing the other layers until they match their mirror opposite layer.

This action is suitable as it will allow you to eliminate the potato-chip effect.

When the mixed copper PCB contains wide areas of copper, it is advisable not to design them as solid planes but as frames.

This assists with eliminating mismatches of copper density within that layer.

Also, it will greatly minimize issues with twists and bows.

Besides, ensure you symmetrically place the power planes during stack-up.

Furthermore, ensure to use an equal quantity of copper weight in every power plane.

Copper balance is vital to signal/power planes, core, and prepreg layers within the mixed copper PCB.

When copper is in uniform proportion within these layers, you will maintain the whole copper balance within the mixed copper PCB.

To balance out an excessive amount of copper in a certain area, fill the symmetrically opposite area with grids of copper.

Besides, the tiny copper grids do not connect to nets thereby will not interfere with the functionality.

Also, ensure that PCB impedance or signal integrity experiences no impact when you conduct this copper balancing method.

What Software Can You Use When Making A Mixed Copper PCB?

A mixed copper PCB design software allows you to bring the board into the physical space.

It allows you to combine the placement of components and routing that ensures you achieve electrical conductivity.

Some of the PCB design software you can use for this purpose entail the following:

  • PCB Artist
  • Pad2pad
  • DipTrance
  • Ultriboard
  • XCircuit
  • CircuitMaker
  • OrCAD
  • PCBWeb
  • Altium Designer 17
  • Eagle PCBs
  • BSch3V
  • Gerbv
  • DesignSpark PCB
  • KICad EDA
  • FreePCB
  • PCB123
  • ZenitPCB
  • CircuitStudio

What Mechanical Alignment Problems May Happen When You Have An Uneven Mixed Copper Distribution On Your PCB?

The existence of uneven copper distribution during mixed copper PCB fabrication can result in the following:


This occurs when the mixed copper PCB experiences cylindrical or spherical curvatures while all four corners retain their plane.


This happens when there is an unintended alteration in the shape of the mixed copper PCB.

When the manufacturing process has high pressure and temperature levels, it can cause the mixed copper PCB to warp.

Warping is also known as the potato chip effect within the fabrication of printed circuit boards.


This happens when one corner, not within the same plane as the other three, experiences a vertical displacement.

When warping occurs, the solder joints and traces experience stress which will damage the mixed copper PCB.

What Are Some Surface Finishes You Can Use On A Mixed Copper PCB?

Surface finishes on mixed copper PCB not only enhance the aesthetics but also protect the elements on it.

The surface finish is intermetallic joints that sit between the solderable portion of bare copper and electronic components of PCBs.

Some of the surface finish you can use include the following:

Immersion Silver

This non-electrolytic chemical surface finish entails immersing mixed copper PCB in silver ion solution.

The advantages include:

  1. The surface is more even than HASL
  2. Affordable than ENIG
  3. Durability equals HASL
  4. Environmentally friendly than HASL/ENIG

The disadvantages include:

  1. Improper handling can cause tarnishes
  2. Soldering should happen within the same day after removing from the storage

Immersion Tin

This is a metallic finish you will deposit using chemical reaction displacement after placing it on copper.

The benefits of immersion tin are:

  1. Lacks lead
  2. Produces flat surfaces
  3. Re-workability

The disadvantages include:

  1. Measuring thickness is difficult
  2. Exposed tin can corrode
  3. Can cause handling damages
  4. Forms tin whiskers
  5. The technique uses carcinogens


This is a common surface finish within the PCB world.

Some benefits of HASL include:

  1. Affordability
  2. Widely available
  3. Impressive durability
  4. Re-workability

Some of the limitations include:

  1. Thermal shock
  2. Uneven surface
  3. Solder bridging
  4. Not suitable for fine pitch
  5. Plugged plated thru-holes
  6. Contain lead element

Organic Solderability Preservative [OSP]

This entails applying a thin protective layer over copper using a conveyorized technique.

The benefits include:

  1. Produces flat surfaces
  2. Affordable
  3. Has no lead component
  4. Re-workable

The limitations include:

  1. Impossible to measure the thickness
  2. Possibility of causing ICT problems
  3. Not suitable for PTH
  4. Requires sensitive handling

Electroless Nickel Immersion Gold [ENIG]

This finish contains double layers of a metallic coat of gold over nickel.

The benefits of ENIG are that it ensures surfaces are flat, durable, has no lead component, and is suitable for plated thru-holes.

Some limitations include:

  1. Complex technique
  2. It is not re-workable
  3. Costly
  4. Can experience damage from ET
  5. Signal loss

Electroless Nickel Electroless Palladium Immersion Gold [ENEPIG]

This is a triple metallic layer coating of gold, palladium, and nickel.

The benefits include:

  1. Produces extremely flat finish
  2. Wire bondable
  3. No risk of corrosion
  4. Solder joints are excellent
  5. Durable
  6. No lead component

The demerits entail:

  1. Limits during processing
  2. Costly
  3. Limitations regarding re-working

Gold Plating

This has a gold-plated layer over the nickel barrier coat.

The benefits are that it has no lead and is durable.

Some limitations include:

  1. Demarcation
  2. Entails use of resist
  3. Costly
  4. Plating is necessary

What Are Some Benefits Of Using Heavy Copper When Making Mixed Copper PCBs?

Some of the advantages include:

  • More strength to thermal strains
  • Available high-power-density transformer planar
  • Enhanced mechanical strength in plated thru-holes and site connectors
  • Use special materials to full capacity with no failure of the circuit
  • A high current carrying capability
  • Minimized size of the products due to incorporation of mixed copper within similar circuitry layers
  • On-board directly plated heatsinks on the surface of mixed copper PCBs using copper planes

What Are The Uses Of Mixed Copper PCBs?

Mixed copper PCBs find their application in the following areas:

  • Central power units
  • Power amplifier systems
  • Heat dissipation devices
  • Power converters
  • Welding tools
  • Electronic power devices
  • Power distribution panels
  • Planar transformers
  • Solar boards
  • High-power distribution systems
  • Radar system power supplies
  • Weapon control units
  • Automotive power distribution units
  • Battery charger units

How Can You Eliminate Unwanted Copper From Mixed Copper PCB During The Fabrication Process?

When making mixed copper PCB, you will attach a sheet of the copper substrate to the board.

Manufactures then form circuits by eliminating copper and leaving behind copper traces.

This is known as the subtractive technique, and there are additive methods that exist for multilayer mixed copper PCBs.

There are various types of subtractive techniques you can use when creating mixed copper PCBs.

These include the following:

  • Silkscreening
  • PCB milling
  • Photoengraving

What Issues May Cause A Mixed Copper PCB To Fail?

Some of these issues, which you can resolve, include the following:

  • Acid traps
  • Silvers
  • Starved thermals
  • Pads with gaps
  • Bad annular rings

Should Mixed Copper PCBs Comply With International Quality Standards?

Yes, these standards ensure that the board is safe for use and meets the required standards.

These standards include:

  • UL
  • CE
  • RoHS
  • IATF16949
  • ISO 9001:2008

How Can You Conduct Silkscreen Printing On Mixed Copper PCBs?

Yes, some silkscreen printing methods you can apply entail the following:

  • Liquid photo imaging [LPI]
  • Manual screen printing
  • Direct legend printing [DLP]

Which Processes Can You Use To Place Electrical Components On Mixed Copper PCB?

The processes you can use include the following:

  • Thru-hole technology

This method entails inserting the lead of electronic parts in pre-drilled holes within the mixed copper PCB.

Afterward, you will solder the lead on pads using a soldering iron or wave soldering technique.

  • Surface-mount technology

This method entails using an automatic machine to precisely place electrical components on the surface of the mixed copper PCB.

What Will Influence The Price Of Mixed Copper PCB?

These include:

  • Choice of material

The materials you use when fabricating PCBs will affect their price.

Some factors that will influence the material for your application include:

  1. Heat transfer
  2. Thermal reliability
  3. Temperature reliability
  4. Performance of signal
  5. Mechanical properties
  • Size

Smaller PCBs need fewer parts thus the production cost will be low compared to larger PCBs needing more parts.

  • Layer number

Multilayer mixed copper PCBs cost more than single or double-sided mixed copper PCBs.

  • Surface finish

High-grade and durable surface finishes will increase the production cost of the PCB.

  • Size of hole

Drilling more holes in the PCB requires more work, especially if it is challenging, and will cost you more.

  • Thickness

A thick PCB fetches a high price than thinner versions.

  • Customization

If you need manufacturers to include special features, you will end up spending more.

How Will You Ensure Mixed Copper PCBs Are Of Good Quality?

There are various testing methods that you can apply to ensure mixed copper PCBs are of good quality.

Some of the main testing techniques include the following:

  • Functional testing
  • In-circuit testing [ICT]
  • Automated optical inspection [AOI]
  • Flying probe testing
  • X-ray testing
  • Burn-in testing

What Are Some Electrical Properties Of A Mixed Copper PCB?

These include:

  • Surface resistivity
  • Relative permittivity
  • Dielectric constant
  • Dissipation factor
  • Volume resistivity
  • Electrical strength

Can You Find Mixed Copper PCBs In Different Colors?

Yes, they are available in several colors such as:

  • Red
  • Green
  • Blue
  • Black
  • White
  • Yellow

For all your mixed copper PCBs, contact us now.

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