Guide

IMS PCB: The Most Comprehensive Guide

Controlling heat in printed circuit boards (PCBs) is more important than ever due to modern electronics’ miniaturization and rising performance requirements. To avoid overheating, efficient heat dissipation becomes more and more crucial as components become smaller and more closely packed. This has inspired people to make creative fixes-insulated metal substrate (IMS) PCBs.
 
This blog will discuss the IMS PCBs (Insulated Metal Substrate PCBs), their benefits, applications, materials, and manufacturing processes, highlighting their importance in high-power and heat-intensive applications.

What is IMS PCB?

First, IMS PCB(Insulated Metal Substrate PCB)is a special PCB that handles high power and heat.IMS utilizes a unique insulating material to press the circuit board copper foil to the metal substrate. The metal substrate is specially treated to increase adhesion and resilience, therefore, it can withstand the mechanical and thermal stresses of many applications. The insulating material is a special blend of ceramic-filled polymers with high thermal conductivity, insulation, and flexibility.

IMS PCB Layers

We all know IMS PCB takes center stage in the electronic industry now. But when we consider manufacturing it. And what kinds of materials can we use? Now let’s find out the answer together. IMS PCB materials are chosen to offer advanced thermal management, electrical insulation, and mechanical strength. The following are the primary elements that form IMS PCB:
The term “substrate” here refers to the underlying material or layer. The lowest layer of an IMS PCB is a metal substrate made of a thermally conductive material, such as aluminum or copper. Aluminum is widely preferred because it is inexpensive, lightweight, and has better thermal conductivity. Copper, on the other hand, is relatively costly. However, it has better thermal conductivity and can support high power densities. The thickness of this layer typically ranges from 0.5 mm to 3.0 mm.

Dielectric Layer

This layer forms the electric insulation between the metallic substrate and the copper traces of the circuit. It is approximately 50–200 micrometers thick. Thin layers of various materials, such as epoxy-based resins and polyimides, can be used. These materials can greatly help address the thermal performance properties of electric insulation.

Copper Traces

The circuit pathways are etched on the dielectric layer through the copper traces, which usually have a width varying from 17 µm to 70 µm. Copper is ideal for this purpose because it has high electrical conductivity and can easily be etched to produce a fine circuit design.
This acts as an insulating protective layer over the copper traces so they do not oxidize, suffer short circuits, or suffer any other damage. The solder mask also plays a great role in isolating the copper traces.
It also provides a good surface for mounting and soldering onto an electronic component’s PCB. Commonly used solder masks are based on epoxy resin, polyester resin, and Liquid Photo Imageable (LPI).
The surface finish in IMS PCBs is very important to ensure proper soldering and sustained function over time. Common surface finishes are HASL (Hot Air Solder Leveling), ENIG (Electrodes Nickel Immersion Gold), and OSP (Organic Solder-ability Preservatives). These finishes greatly improve solder-ability, prevent oxidation, and make the printed circuit boards always less susceptible to damage.

Benefits of IMS PCB

After we briefly understand IMS PCB from the above, we can also briefly summarize some of the benefits it can bring to us.

Enhanced Heat Dissipation

Since the base layer is made from a metal of high thermal conductivity, such as Aluminum, the convective heat transfer rate is higher to the surroundings. In addition, materials with higher thermal conductivity are used for the dielectric layer. This results in a higher thermal conductivity, which keeps the element at a lower temperature.

Improved Reliability

The heating of the circuit boards might cause these boards to expand. Uneven heating can be more problematic, as this often tends to generate thermal stress, which can cause the failure of components. Since the heating issue is adequately addressed in IMS-PCB, there are very low chances, if any, of failure of the components due to stress generated by heat.

Compact Design

Better thermal management allows for more compact and densely packed circuit designs. This is because components can be packed close enough without overheating. Besides, much space can be saved, as additional cooling components such as fans and heat sinks are not required.

Improved Mechanical Strength and Durability

Its metal base provides robust support, reducing the risk of damage from physical stress and vibrations.

Functions as Electromagnetic Shield

The metal layer blocks and absorbs electromagnetic interference (EMI), protecting sensitive electronic parts.

Cost-Effectiveness

By reducing the need for additional ground planes, IMS PCBs can lower manufacturing costs.

Types of IMS Board

IMS PCB boards can be classified into three types, depending on the number of layers used for PCB fabrication and the component mounting location.

Single-Sided IMS PCBs

In this technology, all the components of the PCB are mounted only on one side of the board, whereas the other side comprises a metal substrate with possibly a solder mask. This type of board is suitable for simple designs with basic thermal management needs.

Double-Sided IMS PCBs

These types of PCBs have components placed on the top and bottom sides of the board, thereby allowing for complicated designs and increased thermal performance. They are widely used in power electronics.

Multi-Layer IMS PCBs

This class of PCBs uses several layers of copper traces, combined dielectric material, and interface substrate material. The components can be soldered on one or both sides of the board. This allows for more complex designs and reduces electromagnetic interference.

Manufacturing Process of IMS PCB

Similar to the manufacturing of other PCBs, the manufacturing process of IMS PCB involves the following steps:
Step One: Design Preparation
PCB designers create a detailed layout using CAD software, specifying the placement of components and copper traces. The design is reviewed before it goes into production.
 
Step Two: Material Selection
Appropriate materials are selected for the substrate, dielectric, and circuit layers.
 
Step Three: Base Material Preparation
The base metal with high thermal conductivity is cut into the desired shape and cleaned to remove contaminants.
 
Step Four: Laminating Dielectric Layer
The dielectric layer is then laminated onto the metal base.
 
Step Five: Laminating Copper Foil
Now, on top of the dielectric layer, a layer of copper foil is laminated. This is later made into copper pathways.
 
Step Six: Circuit Pattern Formation
A photo-resist (light-sensitive material) is applied to the copper surface. This material is then exposed to ultraviolet light through a photo mask. Photo masks allow areas of light to harden.
 
Step Seven: Chemical Etching
The entire surface is then etched using a chemical solution. The unhardened surfaces are easily etched out while the hardened ones remain, leaving the desired circuit pattern.
 
Step Eight: Photo-resist Removal 
The remaining photo-resist is washed away. 
 
Step Nine: Drilling and Plating
Holes are drilled for component leads and mounting purposes. These holes may extend through the dielectric layer and into the metal base if required. The drilled holes are then plated with copper to establish an electrical connection between different layers or components.
 
Step Ten: Solder Mask and Surface Finish
A solder mask shields the copper traces and avoids solder bridges. It also offers insulation and defense against outside influences.
 
Step Eleven: Silkscreen Printing
Component identifiers, logos, and other markings are printed onto the PCB by silkscreen.
 
Step Twelve: Inspection and Packaging
It undergoes electrical testing for circuit defects, visual inspection for physical flaws, and thermal testing to verify thermal performance standards. If flawless, it is packed to be taken to market.

Thermal Management Process in IMS PCB

While IMS-printed circuit boards inherently have better thermal performance, they may require some ancillary techniques to ensure good thermal management.

  • First, thermal vias are small, plated holes used to conduct heat from the top layer to the metal substrate of the printed circuit board. An effective arrangement of thermal vias ensures good performance by transferring heat from components to the outside and preventing heat buildup on the board.

  • Another is to increase the cross-sectional area of copper in each layer of the printed circuit board. This increases the heat dissipation area, thus avoiding hot spots. Increasing the width of the copper acts as a heat sink, spreading the heat load across the board.

  • The last practical method of dissipating heat is to install a heat sink on the bottom of the printed circuit board. A heat sink mounted on the bottom of the printed circuit board collects heat from the board and transfers it from the board to the surroundings by free convection. We can also add a fan to improve the thermal conductivity of these radiators.

Standards Used in the Manufacture of IMS PCB

Some of the common standards of IMS PCB will be used include:
 
IPC-2221: They provide guidelines for the design process of PCBs.
 
IPC-6012B: It specifies the certification and performance requirements for fabricating rigid PCBs.
 
J-STD-001: It describes the materials, methods, and other requirements for high-quality soldered interconnections.
 
IPC-TM-650: A guide to determining many aspects of printed circuit board performance, including assessment regarding a PCB’s tendency to allow for surface electrochemical migration

Application of IMS PCB

IMS Printed Circuit Boards find applications in many areas, the main ones being enumerated below:

LED Lighting

High-power LEDs emit a lot of heat. If you have to use a better thermal management aspect of the printed circuit board, IMS printed circuit boards will be your best choice. Enhanced heat dissipation greatly improves the life and performance stability of the LED components.
IMS PCBs are also well-accepted in the automotive industry. Generally, it is used in Engine Control Units and power management systems. This is because these boards can work at higher temperatures and vibrations but confirm to provide stability in performance.

Power Electronics

These types of electronics, consume high currents, are motor drives, power converters, etc. They can get heated very easily. In these kinds of electronics, PCBs are commonly used as IMS.

Consumer Electronics

IMS PCBs enable effective thermal management in laptops, tablets, and smartphones. Such boards are very common in devices that use high-performance computing and gaming.

Industrial Application

The IMS PCBs find wide applications in diverse industries because they hold good qualities in thermal management, mechanical strength, and reliability. The application area includes control systems and robotics, among others.

Challenges in Designing IMS PCB

Material Selection

Getting a dielectric material with a perfect balance between the best thermal conductivity and electrical insulation is hard. This is because, in the main, most materials that are good conductors of heat are good electrical conductors, too. Similarly, all materials used in the PCB (copper, dielectrics, and base metal) must have the same or nearly the same thermal expansion coefficient. This is because the uneven expansion of components can induce thermal stress, which can delaminate the PCB during thermal cycling.

Heat Dissipation and Management

It is pretty challenging to design thermal vias such that heat from the component easily flows through the board, ensuring effective heat dissipation and that the electrical activity of the circuit should not be affected. Further, it is even difficult to ascertain that the components that emit heat are placed so systematically that they draw out the heat dots to the maximum extent while the signal and equipment are fine.

Manufacturing Constraints

Uniform and void-free lamination of the dielectric layer upon the metal base is no easy task. The defects can influence the functionality of the needed thermal and electric performances of the PCB. Surface etching has to be very precise to achieve fine patterns of the circuit on the copper layer, considering that, apart from being thicker, the copper conductivity is much better than that of standard PCBs.

Conclusion

Developed specifically for high-power and heat-intensive applications, the IMS PCB facilitates improved heat dissipation. It enhances the reliability of compact and durable designs. The material itself and the construction of IMS PCBs provide significant thermal resistance benefits, but often, additional measures like thermal vias, thick copper layers, and heat sinks are necessary to achieve best-in-class thermal performance.
 
These boards are used in various areas, ranging from LED lighting to automotive systems, power electronics, and consumer devices. The assurance of effectiveness and reliability is achieved only through careful material selection and accurate manufacturing. Despite the difficulty of both design and manufacturing, material selection, and heat reform, this technology is still critical for all advanced electronics requiring efficient thermal management and durability.
 
If you’re looking to enhance the performance and reliability of your high-power electronic applications, consider the advanced thermal management capabilities of IMS PCBs. Contact FC today to learn more about our custom IMS PCB solutions and how they can benefit your next project. Contact our team now to discuss your requirements and get a free quote!

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