Insulated Metal Substrate (IMS) PCB
- TapRen Team
- 5 hours ago
- 7 min read
Abstract
Heat management is as crucial as power supply in high-power electronics. Insulated Metal Substrate (IMS) PCBs are advanced circuit boards designed for thermal applications, excelling in heat management and suitable for use in various fields, including LED lighting, automotive, and power devices.
This article provides a comprehensive guide to IMS PCBs, covering everything from design and materials to considerations, specifications, and actual applications. This article will also examine the applications of IMS PCBs in modern electronic design.
What is an IMS PCB?
An IMS PCB is an aluminum (typically) metal substrate-based printed circuit board with enhanced heat dissipation. Unlike the fiberglass (FR-4) material commonly found in standard PCBs, IMS PCBs feature a thermally conductive dielectric material between the metal substrate and the copper circuit layer. This design enables efficient heat dissipation from electronic components; hence, IMS PCBs are especially ideal for high-power and high-temperature applications. They are widely used in LED lighting, automobile electronics, and power devices where thermal performance is needed.
Structure of IMS PCB
IMS PCBs are uniquely engineered to address high-temperature situations using a simplified, yet highly effective, layered composition. Each layer of the composition plays a vital role in delivering electrical functionality while managing thermal performance. Let us break down the three main layers that make up an IMS PCB:
Metal Base Layer
This is the foundation of the IMS PCB and is typically aluminum due to its high thermal conductivity and low weight. Recently developed high-performance applications benefit from using copper or stainless steel as an additional heat-dissipation material while increasing mechanical strength. This bottom layer provides mechanical strength to the entire board structure and serves as a thermal sink, transferring heat from sensitive board elements.
Dielectric Layer
Dielectric layer: The dielectric layer is a thin, electrically insulating but thermally conductive material that separates the metal base from the copper layer. It is extremely critical to conduct heat from the copper circuitry down through to the metal base while electrically insulating the electrical paths. The effectiveness of the PCB at dissipating heat is directly affected by the thickness of the layer and the thermal conductivity.
Copper Circuit Layer
This is the topmost layer wherein patterns of electronic circuits are formed. Copper is used due to its high electrical conductivity, which facilitates the flow of current with minimal resistance. This layer's thickness varies based on current requirement, and it connects all the components together while synchronizing with the lower layers to allow heat to be conducted efficiently.
This high level of integration makes IMS PCBs an excellent choice for electronics where overheating can lead to degraded performance or damage.
Application of IMS PCB
IMS PCBs have broad applications in markets where heat management is key to performance and safety. They are ideal for high-power electronic systems in small form factors due to the efficiency of their thermal design. Some of their typical uses include:
LED Lighting
IMS PCBs are used in LED lighting to prevent overheating and maintain constant brightness. The proper distribution of heat works to decrease the normal lifespan of LEDs.
Automotive Electronics
Electric vehicles, along with ADAS and battery systems, utilize IMS PCBs due to their resistance to heat and vibration. Lighting systems, along with engine control units and battery systems, receive stable performance from these components.
Power Supplies
IMS PCBs in inverter and voltage converter applications handle high power loads with electrical efficiency. Their thermal stability provides long-term reliability.
Consumer Electronics
From small chargers to high-performance laptops, IMS PCBs guarantee low device temperatures without relying on heavy cooling systems.
Telecommunication Equipment
They are used in signal amplifiers and RF modules where temperature management provides reliable signal integrity and reduces the failure rate.
Key Materials Used in IMS PCB
The performance of the IMS PCB to a large degree depends on the type and composition of the material. Each layer utilizes materials with high thermal, electrical, and mechanical properties. A brief description of the principal materials used is provided below:
Metal Base
Aluminum is the most commonly used base material because it possesses reasonable thermal conductivity, a low price, and a lightweight nature. Copper can be used to offer enhanced heat performance, and steel adds extra mechanical strength if needed.
Dielectric Layer
This layer consists of electrically insulating yet thermally conductive materials such as epoxy-based or ceramic-filled polymers. This layer provides efficient heat transfer to the metal base without compromising electrical insulation.
Copper Circuit Layer
Copper is used because of its excellent electrical conductivity to form the actual circuitry of the PCB. Thickness will vary (typically 1 oz to 3 oz) depending on the current and power requirements of the application.
Design Considerations on IMS PCB
Designing an IMS PCB requires a thorough examination of both electrical and thermal performance. Unlike other PCB types, IMS boards must be designed to optimize heat flow, component placement, and mechanical reliability. Some of the most important considerations are:
Thermal Management
The primary objective is to achieve adequate cooling of heat; hence, the hottest spots should be near the metal base or, at the very least, have unobstructed thermal paths. Heatsinks and thermal vias can also assist in further cooling.
Component Positioning
The high-power components must be placed in a manner that insulates them from the thermal stress of heat, so that the neighboring components are not heated up. Isolating hot and sensitive components stabilizes them with time.
Layer Thickness
Choosing the right copper thickness ensures safe handling of current, while dielectric thickness affects insulation and heat transfer. Thin dielectrics offer improved thermal performance but require careful consideration of voltage.
Mounting and Drilling
Since IMS PCBs lack the flexibility of regular boards, precise drilling and mounting methods are essential. Mechanism fixtures should ensure non-stressing of the board or damage to the insulation layer.
Cost vs Performance
IMS PCBs are used to achieve high-performance operation, albeit at a possibly increased cost compared to conventional PCBs. Design complexity versus material choice minimizes cost and maximizes performance.
Standard and Testing Used in IMS PCB
To ensure reliability, performance, and safety, IMS PCBs must comply with some industry standards and withstand rigorous testing. These standards confirm that the material and design accommodate actual electrical and thermal stress. The following are the leading standards and tests employed:
IPC-2221
This is a general standard for PCB design, encompassing layout, materials, and construction requirements. For PCBs of IMS, it supplies standardized design procedures along with performance requirements.
UL 94 Flammability Rating
The test determines the ease with which the dielectric material ignites and burns when on fire. The safer the board is to use at high temperatures, the higher its UL 94 rating.
Thermal Cycling and Shock Testing
These tests expose the PCB to thermal cycling in a bid to gauge its tolerance. These tests circumvent cracking, warping, or board failure caused by thermal stress over extended periods.
Dielectric Strength Testing
It is a test to ensure dielectric perfection between the metal base and copper. It prevents any danger of breakdown or short circuit in the event of high-voltage exposure.
Comparison of IMS PCB with Other PCB Types
Feature | IMS PCB | FR-4 PCB | Ceramic PCB |
Heat Dissipation | Excellent | Poor | Very Good |
Cost | Moderate | Low | High |
Mechanical Strength | High | Medium | High |
Applications | High-power, LED | General electronics | High-frequency, RF |
Weight | Moderate (Aluminium) | Light | Heavy |
Case Studies
Case Study 1: Graphite Embedment IMS for Enhanced Thermal Management
Oak Ridge National Laboratory researchers developed an insulated metal substrate with embedded pyrolytic graphite (IMSwTPG) to improve the thermal performance of wide-bandgap (WBG) power modules. Through the use of thermally annealed pyrolytic graphite in the IMS, they achieved a decrease in junction-to-case thermal resistance of up to 17% and an increase in device current density of up to 10%. This demonstration showcases the capability of graphite-enhanced IMS to enhance the efficiency and reliability of high-power electronic systems.
Case Study 2: Comparative Evaluation of IMS and DBC Substrates for High-Power Modules
Researchers, in a journal article published in the Journal of Electronic Packaging, presented a detailed comparison of insulated metal substrates (IMS) and direct-bonded copper (DBC) substrates for high-power module applications of high-power wide-bandgap semiconductors. According to the researchers, IMS substrates exhibit improved transient thermal performance, resulting in lower junction temperatures during low-frequency operation. In other words, IMS can serve as a good alternative to traditional DBC substrates for applications where thermal management is badly needed.
Key Takeaways
The combination of a metal substrate, dielectric layer, and copper circuit makes IMS PCBs an excellent choice for thermal management solutions in electronic systems specifically designed to support high-power and heat-intensive applications.
The metal substrate, combined with the dielectric layer and copper circuit composition of these materials, enables enhanced heat transfer and improved performance while enhancing durability. The rising needs in the automotive, power electronics, and lighting sectors continue to drive the development of IMS PCBs.
Seeking a dependable solution for heat management in your electronics? At TapRen, we specialize in high-performance IMS PCBs designed for LED lighting, electric vehicle (EV) systems, power supplies, and other applications. With expert support, custom stack-ups, and fast delivery, we make sure your boards perform under pressure every time. Contact us or request a quote today to begin your IMS PCB project.
FAQs
Are IMS PCBs appropriate for bendable or flexible designs?
No, IMS PCBs are rigid by nature due to the metal base. They are not well-suited for bendable or flexible applications. Flexible PCBs made of polyimide or other flexible materials are utilized for these purposes.
What is the effect of the dielectric layer thickness on thermal performance?
A thinner dielectric layer will increase thermal conductivity by reducing the path for heat transfer. It must still provide adequate electrical insulation, however, so there is always a trade-off between thermal and electrical considerations.
Are IMS PCBs recyclable or environmentally friendly?
IMS PCBs are partially recyclable, particularly the metal base, such as copper or aluminum. Recycling the entire board is more complex due to the bonded layers. Businesses today are investigating more sustainable materials to promote environmental sustainability.
Do IMS PCBs handle high-frequency signals, such as radio frequency (RF) or microwave signals?
While IMS PCBs excel in thermal management, they are not typically used for very high-frequency applications unless blended with special low-loss dielectric materials. Ceramic or PTFE-based boards are better suited for RF and microwave circuits.
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