FERRO Material

Choosing a suitable PCB material can be an overwhelming task – a reason this guide will explore all the fundamental aspects you need to know about FERRO materials.

So, if you want to learn more about this material, then read this guide.

What Is FERRO Material In PCBs?

FERRO materials encompass ferromagnetic materials which exhibit significant and positive response when subjected to an external magnetic field.

They have a significant affinity to magnetic fields and can keep their magnetic characteristics even when you eliminate the external field.

FERRO materials include some unpaired electrons, resulting in a net magnetic moment in their atoms. The existence of magnetic domains gives them their strong magnetic characteristics.

The domains align when you apply a magnetizing force, resulting in a high magnetic field within the part. FERRO materials you can employ in PCBs include iron, nickel, and cobalt.

FERRO material for PCB

What Are Some Of The FERRO Materials You Can Employ In PCBs?

You observe that FERRO materials possess unpaired electrons in individual atoms, molecules, or ions. They also share the same spin angular momentum orientation and are capable of forming magnetic domains with magnetically aligned atoms.

You consider the following metals as FERRO materials:

Iron

You consider other metals possessing this ability similar to iron due to its abundance and versatility as a natural permanent magnet.

You can employ iron as a component of steel which is a high-temperature iron alloy strengthened with carbon.

Cobalt

Cobalt is a metal that you frequently find in ore with copper and nickel.

You find cobalt, unlike iron, is very corrosion resistant thus finding use in PCBs employed in harsh environments.

Magnetite

Magnetite is a FERRO material with a lustrous sheen that is not technically a metal. Magnetite forms via the oxidation of iron into an oxide.

Nickel

Nickel is a transition metal, and the third of the three major FERRO materials alongside iron and cobalt. Nickel is essential to the electroplating process, allowing us to use PCBs in several electrical devices.

Where Do You Employ PCBs Made With FERRO Material?

PCBs possessing FERRO materials in their construction find use in various applications such as:

• Automotive sensors including power converter boards and engine control units.
• In making semiconductor packaging and components such as ceramic capacitors and EMI filters.
• Aerospace and defense specific boards employ FERRO materials.
• You find these material in circuit boards utilized in medical appliances.

How Does Curie Temperature Affect FERRO Material In PCBs?

The Curie temperature of a FERRO material is the temperature beyond which the material loses its permanent magnetic qualities.

You can however still induce magnetism to these materials in most circumstances.

Thermal entropy competes with the ferromagnetic inclination for dipole alignment as the temperature rises.

A second-order phase transition occurs when the temperature exceeds the Curie temperature, causing the system to lose spontaneous magnetization.

What Thermal Properties Are Essential For FERRO Material Used In PCBs?

Some of the essential thermal properties when using FERRO material on PCBs are as follows:

Temperature Of Glass Transition (Tg)

The temperature of glass transition describes the temperature range a PCB material transforms.

The transformation is usually, from a glassy solid state to a pliable one as polymer chains exhibit movement.

The properties of the material return to their original states after it cooling. You describe the temperature of glass transition in degrees Celsius (^oC).

Temperature Of Decomposition (Td)

The temperature at which a PCB FERRO material chemically decomposes is its decomposition temperature measured in degrees Celsius (^oC).

When building PCBs, the Td of a material is critical because changes to its properties are irreversible.

You need to select a FERRO material that allows you to work at temperatures higher than Tg but lower than Td.

Most solder temperatures during PCB assembly are between 200 and 250 degrees Celsius, thus ensure Td is higher.

Thermal Expansion Coefficient (CTE)

You define the expansion rate of a PCB FERRO material as its temperature rises as the coefficient of thermal expansion.

You measure CTE in parts per million (ppm) exhibited upon respect rise in degree Celsius.

When the temperature of a FERRO material exceeds Tg, the CTE rises with it.

You need to ensure your material’s CTE in the z-axis should be on the lower side.

Thermal Conductivity (k)

Thermal Conductivity is the ability of a FERRO material to carry heat measured in watts per meter per degree Celsius (W/M/^oC).

Where your material has low thermal conductivity, it signifies poor heat transfer, whereas high conductivity means great heat transmission.

What Electrical Properties Are Important When Selecting FERRO Material For PCBs?

Electrical properties of FERRO materials speaks to their ability to conduct electric current. These include:

Relative Permittivity

The relative permittivity of a FERRO material influences signal integrity and impedance which in turn influence electrical performance at high frequency.

The relative permittivity fluctuates with frequency decreasing with a rise in frequency.

Dissipation Factor

The dissipation factor of a FERRO material represents the amount of power lost as a result of the substance.

You lose less power when your material has a lower dissipation factor.

Frequency changes also affect the dissipation factor which increases with a frequency increase up to 1GHz.

For analog signals, it is critical since it controls the extent of signal attenuation and, therefore, the signal to noise ratio.

Electrical Resistivity

The higher the electrical resistivity of a FERRO material, the less easily it permits electric charge to travel.

Moisture and temperature influence electrical resistivity which you measure in ohm-meters (Ω-m) or ohm-centimeters (Ω-cm).

Surface Resistivity

Surface resistivity (S) refers to the electrical or insulating resistance of a PCB FERRO material’s surface influenced by moisture and temperature.

Surface resistivity in PCB FERRO materials has to be very high over millions of mega-ohms per square.

What Chemical Requirements Are Necessary For Using FERRO Materials In PCBs?

When using FERRO material in PCBs, the following chemical requirement are essential:

FERRO PCB material

Absorption Of Moisture

Moisture absorption refers to a PCB FERRO material’s capacity to resist water absorption upon immersion.

You calculate it as a material’s percentage increase in weight stemming from water absorption under controlled settings and conventional test procedures.

Moisture absorption influences the FERRO material’s thermal and electrical properties.

It is also influential in determining a material’s capacity to prevent the development of conductive anode filament (CAF).

Resistance To Methylene Chloride

Methylene chloride resistance is a metric for a PCB FERRO material’s chemical resistance, especially capacity to withstand absorption of methylene chloride.

You measure it as a percentage increase in the weight of a material owing to regulated exposure to methylene chloride.

What Mechanical Properties Should FERRO Materials Possess In PCBs?

Mechanical properties of materials in PCBs are essential for the board’s structural integrity. These properties include:

Peel Strength

The binding strength between the copper conductor and the dielectric material defines peel strength provided in pounds per linear inch.

It measures the amount of force necessary to separate bonded materials at a separation angle of 180 degrees.

Flexural Strength

The ability of a FERRO material to sustain mechanical stress without fracturing defines its flexural strength.

You determine the PCB material’s flexural strength by providing end supports and loading the middle. The unit of measurement is pounds per square inch.

Tensile Modulus

Tensile modulus, is a strength measurement for PCB FERRO materials usually provided instead of flexural strength.

Tensile modulus assesses the stress/strain ratio in a specific direction and described as the force per unit area.

Time To Delamination

At a given temperature, the time to delamination measures the time it takes a material to withstand delamination.

Delamination involves separation of the resin from the laminate.

Thermal shock, the improper glass transition temperature, moisture, and inferior lamination technique can induce delamination.

What PCB Board Types Can You Employ FERRO Materials?

You can employ FERRO materials in the following PCB types:

Single layer vs double layer PCB

• Single Layer PCBs: Forms the majority of board types with the simplest deign and least manufacturing costs.

Possess just one conductive layer for component attachment.

• Double Layer PCB: One conductive layer is above a non-conductive substrate, while another below it.

You can employ vias to link pads on both board to join the two conductive layers.

• Multi-layer PCB: Describes a circuit board with three or more conducting layers.

At least one conductive layer is between the non-conductive substrate and the top and bottom conductive layers.

• Rigid PCB: The substrate material is a solid structure that doesn’t yield to bending or folding. Provides mechanical support to the board.

What Are Important Guidelines When Furnishing PCBs From FERRO Materials?

Keep the following guidelines in mind while choosing FERRO materials for your PCB:

Dielectric Constants Must Match

The dielectric constants of the FERRO material and other board constituents have to match to prevent performance issues.

Cost

FERRO materials can cost a lot of money, however you get the best properties for various board functions.

Use Smooth And Conductive Foils

Smooth copper foil reduces losses at high frequencies whereas poor conductors can cause circuit dampening.

Match Thermal Expansion Coefficient

A mismatch of the CTE for POCB materials inclusion FERRO materials can cause separate expansion rates detrimental to the board structure.

Can You Employ FERRO Materials In High Frequency PCBs?

With high-frequency circuits, you process small or precise signals.

The ability of the circuits to process low-level signals correctly is dependent on a package with least losses possible.

Losses arise as a result of reflections where impedances vary with signal absorption in the PCB materials. FERRO materials offer you great signal absorption preventing losses.

You can track variations in impedance to losses caused by reflections.

Additionally, variations in laminate thickness, dielectric constant, and trace width all contribute to these issues.

You can house a high-frequency circuit in a two layer PCB or more when using FERRO materials due to reduced complexity.

Consequently, you can laminate one or more layers given the reduced losses and dielectric properties.

Why Do You Need To Drill Holes Through FERRO Materials In PCBs?

Cut-outs, slots, and the general shape of the finished board entail fabricated properties of a raw circuit board.

The holes drilled into the board have the greatest importance.

There are three types of holes, each with a different purpose as follows:

Via Holes

You carry electrical signals for both power and ground through the board layers using vias which are small plated holes.

Vias come in a variety of shapes and sizes depending on the application including through-hole, buried, blind, and micro vias.

Vias

Component Holes

While most board components are surface mount, many others are still better attached via through-hole packaging.

These typically include switches and other mechanical parts requiring more secure mounting.

Mechanical Holes

Mechanical features you attach to a PCB including fans and brackets require holes for attachment.

These holes are typically unplated but can be when an electrical board connection is necessary.

You can use mounting holes to distribute heat from hot components to the inner plane layers.

When you employ such holes in the fabrication process, they are tooling holes.

What Are Some Of The Drilling Guidelines For PCBs Using FERRO Material?

There are a few ways that you can approach the drilling process on a circuit board employing FERRO material:

Same Drill Diameter

Your board can entail a lot of drills sharing similar diameter thus requiring a change of drill bits during the process.

Switching may beget tolerance issues which you can overcome by changing some of the drill sizes.

Minimum Drill Diameter

Employ mechanical drill sizes in relation to the board thickness. Drilling with lower drill diameters is difficult, and also plating due to the smaller drill aspect ratio.

Avoid Blind And Buried Vias

Only use blind and buried vias when required for high-density architecture or high-speed circuits.

The process of constructing blind and buried vias increases the cost of board fabrication significantly.

What Drilling Techniques Can You Employ In PCBs Utilizing FERRO Materials?

There are two major drilling techniques available during PCB fabrication: mechanical and laser drilling.

• Mechanical Drilling: Mechanical drills are less precise, but they are simple to use.

You employ drill bits in this drilling technology for holes exceeding a diameter of about 6 mils.

Mechanical drilling PCB

• Laser Drilling: With laser drills you can furnish far tinier holes with workpiece and the tool avoiding each other throughout the operation.

Depth control is easy with possibilities of making blind and buried vias.

Laser drilling PCB

What Aspects Do You Consider When Drilling PCBs With FERRO Material?

When drilling a PCB composed of FERRO material, you consider two major aspects:

• Aspect Ratio: The ability to successfully plate copper inside vias defines the aspect ratio.

Plating smaller holes is time consuming thus requiring use of plating bath.

• Drill to Copper Clearance: Constitutes the area around a drilled hole’s edge and copper feature. This value is typically about eight mils and a minor variation can disrupt the circuit.

What Problems Can You Experience When Drilling FERRO Materials In PCBs?

Some of the problems you experience when undertaking the drilling process include:

• Shifting of the drill from the intended axis can hinder hole accuracy.
• The drilled hole can have rough walls resulting in non-uniform plating.
• Friction during the drilling process produces heat which melts the resin.
• Burrs can manifest at the drill entry and exit points.
• The layers can exhibit separation in a delamination process.
• Copper formations as nail heads can result from the process.

What Are Some Of The Guidelines In Drilling PCBs Composed Of FERRO Materials?

When drilling FERRO material PCBs, you need to consider the following tips:

• Keep the aspect ratio to a minimum to prevent wear resulting from drilling.
• Use a minimal number of drill sizes to reduce the drill time.
• Check for connection created by non-plated holes and the hole description.
• Identify any drills and copper features positioned beyond the profile of the board.
• Compare the drill tolerance with the vias ensuring they conform to desired aspect ratio.
• Check out the filling requirement of vias and the provided fabrication guidelines.

How Do You Etch FERRO Materials In PCBs?

Etching is the removal of material from a surface to reveal a desired design or patter.

You commonly employ liquid chemicals in the etching process alongside plasma and laser methods.

• Chemical Etching: Chemical etching is a subtractive manufacturing method that employs chemical for material removal.

The procedure entails immersing the material in a caustic chemical that reacts with the cut region dissolving it.

• Laser Etching: You employ a high-powered laser to shape out the substrate’s trace via computer control.

The energy in the laser beam alters the material’s chemical makeup, allowing its release via flaking or evaporation.

• Plasma Etching: In this process, you focus a high-speed plasma stream composed of gas combination towards a material.

Plasma etching is simple without any wet residue that reduces chance of contamination and improves the board’s dimensional tolerances.

In case you need any FERRO material or PCB material, Venture is here to help – contact us now.