IMS PCB: The Ultimate Frequently Asked Questions Guide

What is IMS PCB?

IMS is an abbreviation for insulating metal substrate.

The IMS circuit board uses metal as the substrate, next to which is a thin dielectric layer and a copper film.

Due to configuration reasons, many IMS PCBs are single-panel, so only one side of the component connection is supported.

You can use screws and grease to connect the radiator to the bottom plate for heat dissipation.

Compared with traditional circuit boards, the use of IMS PCB can achieve excellent heat dissipation.

Using IMS PCB is one of the most direct ways to keep surface mount components cool.

What metals can you use in IMS PCB?

When using IMS PCB, you can use the following metals as the substrate：

aluminum

Aluminum has both metallic and non-metallic properties and is one of the most widely used elements on earth.

You extract aluminum from bauxite through the manufacturing process and convert it into a useful form.

You can make aluminum alloys by combining with metals such as magnesium, silicon, zinc, copper, and manganese.

Compared with pure aluminum, combining with other metal elements improves processability, electrical conductivity, strength, density and corrosion resistance.

Aluminum has high ductility and can form thin sheets.

On the other hand, its high ductility allows you to easily shape aluminum materials for use in IMS PCBs.

copper

You can find copper from sulfide, carbonate, and oxide mines as a by-product of silver production. Copper and its alloys are one of the most adaptable engineering materials.

Copper is very useful in industrial applications because of its unique combination of properties (including conductivity, machinability, corrosion resistance, ductility, and strength).

Changes in structure and production methods can further improve these qualities.

Some of the characteristics of copper and its alloys that are allowed to be used in IMS PCBs include：

Excellent thermal and electrical conductivity.

Impeccable corrosion resistance.

Excellent machinability, maintaining mechanical and electrical properties at low temperatures

Pure state high melting point 1083o

The conductivity of copper is second only to that of silver, reaching 97% of that of silver.

Due to the availability and cost of copper, you use copper in IMS PCBs.

Stainless steel

Stainless steel refers to a group of iron-based alloys that are corrosion-resistant and heat-resistant.

A distinctive feature of stainless steel is its chromium content of 10.5%, which has higher corrosion resistance than other steels.

You can also use molybdenum, nickel, nitrogen and magnesium in alloy stainless steel.

The minimum chromium content is 10.5% steel provides up to 200 times more corrosion protection than chromium-free steel.

You appreciate its use in IMS PCBs because of its strength, durability, processability, low maintenance, environmental protection, recyclability, and heat resistance.

Stainless steel does not need to be treated regularly through coating and painting after use.

Why use IMS PCB?

Similar to the thermal stress manifested in the processor, it can cause the circuit board to run poorly or even fail.

With the advancement of technology and the miniaturization of equipment, the possibility of thermal stress has increased significantly.

You will find that in today's circuit boards, you can tightly stack components in a reduced form factor.

Therefore, effective and proper management of heat in the PCB is essential to prevent complete loss of equipment function.

The use of IMS PCB is an effective thermal management technique for dissipating heat from the main components of the circuit board.

Such components include LEDs and transistors that generate a lot of heat.

Where do you use IMS PCB?

IMS PCB is suitable for high-power applications that require large mechanical loads and impeccable dimensional stability.

You will find that these PCBs allow you to use thinner traces, achieve higher component density, and extend the life of your products.

Components such as LEDs and transistor generate a lot of heat, and you can easily eliminate this heat using IMS PCB.

When you use an insulated metal substrate, you can get ten times higher thermal conductivity than ordinary FR4.

Some common applications of IMS PCB include：

LED lighting

LED circuits are becoming smaller and smaller, energy-saving and high power output.

You use IMS PCBs in LED circuits because they can effectively absorb the heat generated by LED components.

Automobile manufacturing industry

Hyundai cars are composed of hundreds of control units. You will find these small computers around the engine area exposed to extreme temperatures.

IMS PCB has the thermal conductivity and mechanical properties required for these applications.

Power supply circuit

The power supply circuit uses switching devices that generate a lot of heat.

IMS PCB can effectively transfer heat without installing discrete heat sinks for each component, which can achieve a smaller design.

Solid state relay

We recommend using a solid state relay (SSR), a modern successor to a mechanical relay, including an optocoupler and a MOSFET.

These components are tightly encapsulated in a small housing, which can also be used as a heat sink.

You use the IMS PCB to collect heat from the components and transfer it to the housing to eliminate it.

What material quality does IMS PCB need?

When evaluating an IMS PCB, you need to consider both the mechanical and electrical quality of the substrate.

Some key features are as follows：

Dielectric constant: Compare the capacitance of the substrate material with the vacuum capacitance as the dielectric.

Coefficient of thermal expansion (CTE): Measures the degree of change in the z-axis direction of the metal substrate when it is heated.

Glass transition temperature (Tg): The material no longer functions as a hard material and enters a plastic state.

Decomposition temperature (Td): Determine the heat resistance of the material that affects its physical structure.

Delamination time: Monitor the time oC required for the substrate to delaminate at temperatures of 260 and 288, respectively.

Compare the leakage trace index: measure the electric breakdown quality of the substrate.

What are the advantages of using IMS PCB?

Using IMS PCB can provide you with the following advantages：

The thermal conductivity of IMS PCB is ten times higher than that of traditional FR4 PCB.

The thermal conductivity on the IMS PCB ranges from 1 to 12 W/mK

You can use a thick metal substrate as the structural support of the device in the IMS PCB.

You can tightly package components that emit high heat in the IMS PCB to form a compact device.

You found that this is possible because you have experienced efficient heat conduction on these boards.

IMS PCBs are less susceptible to fire than FR-4 PCBs because they use metal as the substrate.

Therefore, you can use IMS PCBs in high-power applications or combustible environments or high-temperature environments.

When using IMS PCB, you can withstand the electromagnetic shielding provided by the metal substrate.

You can also use a metal substrate as a ground plane, eliminating the need for additional wiring, thereby saving costs.

It is easier to use surface mount equipment with IMS PCB because the circuit board can immediately absorb and dissipate the heat generated.

What are the types of IMS PCBs?

You can divide the IMS PCB and the type of metal used as the substrate into the following categories：

Aluminum IMS PCB: Due to its low cost, many IMS PCBs use aluminum as the substrate material.

Aluminum is also lighter than copper, and its thermal conductivity is close to that of copper.

Stainless steel IMS PCB: You use stainless steel where the mechanical strength of the IMS PCB is required.

Stainless steel is even cheaper than aluminum, but compared with copper and aluminum, it has the lowest electrical conductivity.

Copper for PCB: Compared with aluminum and stainless steel, copper provides you with excellent thermal conductivity, so the cost is much higher.

In addition, you find that copper is heavier and easier to corrode than aluminum and stainless steel.

How to configure IMS PCB？

You can configure the IMS PCB in the following ways：

unilateral

When using a single-sided IMS PCB, you install components on one side.

Only one side of this IMS PCB can be used to install components.

There is a layer of copper next to the metal substrate, which can double as a heat sink.

Two-layer single-sided component installation

In this configuration, you use a pair of copper layers to accommodate additional circuits.

However, you only need to fill one copper layer, and you can use FR-4 film between the copper layers. The thermal conductivity of the circuit board can be enhanced by using through holes that connect the component layer to the substrate.

Double-sided component installation

You can fill two conductive copper layers in this configuration.

You use through holes to clamp the metal substrate in the middle to transmit heat and current signals.

The mechanical quality of these PCBs is improved through resin-insulated carrier flow holes. However, the quality of the heat sink of the metal substrate is reduced because it is located in the middle.

Multi-layer with double-sided component installation

An IMS PCB with this arrangement is the most complex, containing multiple copper layers on either side of the metal substrate.

You can install components on two external copper layers for higher density and functionality.

IMS PCB VS FR-4 PCB

The basic requirements between IMS PCB and FR-4PCB are in terms of performance and time.

IMS PCB provides you with better thermal conductivity than traditional FR-4 boards, and its rigid structure enhances the mechanical strength of the board.

Other differences are as follows：

When in use, a single layer of through-hole assembly FR-4 circuit board can be placed.

However, it is impractical to use through holes in a single-layer IMS PCB.

The thermal conductivity of IMS PCB is better than that of similar FR4 PCB.

You can only use a white solder resist layer for IMS PCB. FR4 PCB has a wide range of color options, including green, yellow, black, blue, etc.

When manufacturing IMS PCB, due to the metal substrate material, you need to use special machinery, such as diamond-coated blades.

FR-4 is manufactured using standard equipment and machinery.

When making FR-4 PCB, there can be multiple layers. IMS PCB is only most effective when it is single-layer.

Compared with IMS PCB, you can provide a larger thickness FR-4 PCB.

Exceeding the thickness of the cetin of the IMS PCB will invalidate its effectiveness in terms of thermal conductivity.

What surface treatment can you use on IMS PCB?

PCB surface treatment is a metal coating that you apply to the traces to protect the copper below from oxidation.

Corrosion of conductive copper traces can cause signal flow to be interrupted, resulting in failure.

Some of the surface treatments you use for IMS PCB include：

Tin spray/lead-free tin spray

Hot air solder leveling is the most common surface finish in circuit board manufacturing.

You dip the circuit board into the molten tin/lead alloy, and then use hot air to blow off the excess solder.

In lead-free HASL, since lead is classified as a restricted hazardous substance, you can replace lead with other metals.

HASL exposes your circuit board to high temperatures, allowing you to highlight any layering problems before the components are assembled.

OSP (organic weldable preservative)

OSP is a type of water-based surface treatment used to protect copper pads from corrosion. OSP has low maintenance costs, provides a coplanar surface, and is lead-free and environmentally friendly.

Nevertheless, it lacks the durability of HASL and is delicate to the touch.

Electroless nickel-plated immersion gold (ENIG)

ENIG contains a pair of layers on copper composed of nickel and gold metals.

Nickel provides copper protection as the actual welding surface of the component.

Gold protects nickel during storage and provides low contact resistance.

Because it complies with RoHS, it is a popular surface treatment that can provide you with a smooth surface while providing a long shelf life.

silver immersion

In silver immersion, you chemically treat copper by immersing a certain amount of silver ions. This process is a non-electrolytic process, which can provide an excellent finish for EMI shielded circuit boards.

With this surface treatment, you can get an average surface thickness between 5-18 micro inches.

Compared with ENIG, the surface treatment is environmentally friendly and the cost is lower.

tin immersion

By chemically depositing tin directly on copper, you can achieve metal surface treatment by immersion.

Copper and tin form a firm bond, thereby forming a permanent antioxidant protective layer.

Since the process does not use lead, it is environmentally friendly. In addition, you can also get a reworkable plane.

How to solder IMS PCB?

Welding IMS PCB on the welding wave does not require changing the welding technology.

You pump the tin into the assembly holes from below and immediately connect them to the copper wall of the drill bit.

However, depending on the type of IMS board, reflow soldering may require certain adjustments to the welding curve.

In the reflow soldering process, the main advantages of IMS PCB are against you.

You noticed that the ability to dissipate heat effectively makes the pad heat up more slowly. In order to change the welding curve, you found that there are two influencing factors：

Metal substrate thickness and circuit board size.

The durability of the components limits the peak temperature, making the residence time before the melting point the only modifiable process variable.

At this time, make sure that there is enough circuit board heating to prevent less heat from being discharged at subsequent peaks.

Why is aluminum better than copper in IMS PCB?

IMS PCB uses a metal substrate to improve the thermal and mechanical properties of the circuit board.

Compared with similar circuit boards using FR-4 substrates, the use of metal substrates can increase the thermal conductivity by XNUMX times.

Aluminum is usually used as the substrate material for such boards because it is cheap and light in weight.

Although copper has higher thermal conductivity and lower CTE, the cost of using it for high-density designs is much higher.

What etching techniques have you applied to IMS PCB manufacturing?

You use etching technology to selectively remove the surface of the substrate or layer that is consistent with the design.

You can use wet etching or dry etching on the IMS PCB.

Wet etching

Wet etching is a method of immersing a material in a widely used etching solution.

The three factors that affect the etching rate are: stirring, the concentration of the etching solution, and the temperature of the etching solution.

Wet etching is an isotropic process.

When you increase the etching temperature and implement stirring, you can significantly increase the etching rate.

Dry etching

Dry etching is the most common method of etching submicron-sized objects because it uses plasma to etch thin layers.

The plasma initiates a reaction with the surface layer, resulting in volatile chemicals.

You can also use plasma to directly attack the surface of the film. The dry etching process is anisotropic.

What are the characteristics of the etching process in IMS PCB?

You can characterize the etching process based on the technology used (i.e. wet etching or dry etching).

Some features are as follows：

For wet etching, although it is cheap, you can use it to remove all metals in the PCB while obtaining a uniform surface.

Wet etching is highly selective, and you can perform surface treatment without damaging the surface.

You used a physical ion sputtering mechanism in dry physical etching to achieve a fast etching rate.

Dry physical etching allows line width control, thereby simplifying the process of having anisotropic side wall contours.

Dry chemical etching is a slow process that involves chemical interactions between active elements.

Using isotropic sidewall contours, it is difficult to achieve line width control in dry chemical etching.

What are the thermal management alternatives for IMS PCB?

Thermal management is essential for high-power circuit boards that emit a lot of heat.

If left unmanaged, the accumulation of heat on the surface of the circuit board can cause strain, which can hinder function and even cause damage.

The use of IMS PCB is an effective way to suppress the accumulation of heat on the circuit board.

However, if you have a large number of layers or face cost constraints, you can adopt other alternatives.

Thermal management alternatives for IMS PCB include：

Thermal through holes are used, which are small electroplating holes connected to the PCB layer, creating a continuous path for heat transfer.

A thick copper layer is used to increase the surface area of heat dissipation and heat dissipation.

You can connect a heat sink to the bottom of a traditional circuit board to collect heat to eliminate it from the outside through convection.

What copper thickness can you use in IMS PCB?

The copper thickness in the circuit board design determines the current carrying capacity of the PCB. The unit of measurement of copper thickness is ounces, usually a measure of weight.

However, the ounce measurement value describes the thickness achieved when the copper weight is placed in the square foot area.

For example, an ounce of copper will weigh 1.4 mils in thickness.

When manufacturing IMS PCBs, you can use copper thicknesses of 0.5 ounces, 1 ounce, 2 ounces, and 3 ounces.

You basically identify these copper weights as standard copper weights and weights over 3 ounces as thick copper.

You find that using thick copper on IMS PCBs will offset the thermal conductivity advantages required to use metal substrates.

When working on IMS PCB, how to minimize drilling defects?

The drilling process allows you to provide holes for component connections and inter-layer connections.

This is a precise process that requires precise performance to prevent circuit board damage.

You may encounter defects during drilling, you can minimize them as follows：

Decontamination: You use this chemical procedure to remove the molten resin accumulated on the drilling wall.

Deburring: motorization is used to eliminate burrs, which are protruding extensions of copper formed during drilling.

Layering: The layers in the PCB need to be separated during the drilling process, and you can minimize them by using laser drilling.

What is the thermal conductivity of IMS PCB?

Thermal conductivity refers only to heat conduction, not through convection or radiation. You use the coefficient Watt per Kelvin (W/K) to represent the conductivity affected by the size of the IMS PCB.

When choosing a material for an IMS PCB, you will consider the thermal impedance because it affects the thermal conductivity.

The thermal resistance of a material refers to its internal resistance to the flow of heat.

Materials with low thermal resistance indicate greater thermal conductivity.

Thermal impedance has similar aspects to thermal resistance, but refers to the constant of the contact surface.

When the breakdown voltage is not significant during material selection, you can use a thin dielectric with reduced thermal conductivity.

You can get a similar thermal impedance in this way.

What are the standards you use when manufacturing IMS PCBs?

By guiding the manufacturing process of IMS PCB, standards are essential for product quality assurance.

Some common standards include：

IPC-2221: Provides guidelines for the PCB design process.

It includes functions such as design layout, materials, mechanical quality, parts inventory, thermal management, and electrical characteristics.

IPC-6012B: Specifies the certification and performance requirements for rigid PCB manufacturing.

It sets standards for conductor spacing, weldability, and structural integrity for various product groups.

J-STD-001: Specifies the materials, techniques, and other requirements for high-quality welding interconnection.

It emphasizes process control and highlights the specifications of various electronic products.

IPC-TM-650: A set of rules used to evaluate several elements of a printed circuit board, such as testing the surface electrochemical migration tendency of a PCB.

You can also determine the current resistance on the surface of the substrate and evaluate the ion cleanliness of the circuit board.