PIM vs. Discrete IGBT: A Strategic Choice for Power System Design

August 1, 2025710 Views 8 min read

PIM vs. Discrete IGBT: A Strategic Choice for Your Next Power System

In the world of power electronics design, engineers constantly face a fundamental decision: build a power stage from the ground up using individual components, or leverage a highly integrated, pre-packaged solution? This choice is perfectly encapsulated by the PIM versus discrete IGBT debate. On one side, you have the ultimate flexibility of discrete components; on the other, the streamlined efficiency of a Power Integrated Module (PIM). This decision is not merely about component selection; it dictates the entire project’s trajectory, impacting design cycle time, manufacturing complexity, system size, and overall reliability.

For engineers designing motor drives, power supplies, or inverters, understanding the nuanced trade-offs between these two approaches is critical. Choosing incorrectly can lead to budget overruns, missed deadlines, or a final product that is unnecessarily large and complex. This article provides a comprehensive, experience-based comparison to help you determine which strategy—integration or flexibility—is the winning one for your specific application.

Understanding the Contenders: What are PIMs and Discrete IGBTs?

Before diving into a direct comparison, it’s essential to clearly define our two contenders. While both use IGBTs as the core switching element, their implementation philosophy is worlds apart.

The Discrete IGBT Approach: Maximum Flexibility, Maximum Complexity

A discrete solution involves building the power circuit from individual, separate components on a Printed Circuit Board (PCB). This typically includes:

Six or more individual IGBTs for a three-phase inverter.
Six or more corresponding freewheeling diodes (FWDs).
Separate rectifier diodes for the front-end.
A separate IGBT and diode for a brake chopper circuit, if needed.
Individual gate driver ICs for each IGBT.
Associated passive components (gate resistors, capacitors, etc.).

This approach gives the designer complete control. You can hand-pick the absolute best IGBT for your switching frequency, pair it with a specific low-recovery diode, and meticulously lay out the PCB to optimize current paths and minimize parasitic inductance. It’s the path of ultimate customization, but it places the full burden of thermal design, electrical layout, and component interaction squarely on the engineering team.

The Power Integrated Module (PIM) Approach: A System-in-a-Package

A Power Integrated Module, often referred to as a CIB (Converter-Inverter-Brake) module, is a single, encapsulated component that integrates multiple power semiconductor stages. A typical PIM for a motor drive application includes:

Input Rectifier: A three-phase diode bridge to convert AC input to a DC bus.
Inverter Stage: A three-phase bridge of six IGBTs and six freewheeling diodes.
Brake Chopper: A single IGBT and diode for dissipating regenerative energy.
Thermistor: An integrated NTC thermistor for direct temperature monitoring of the module’s baseplate.

Leading manufacturers like Mitsubishi Electric and Semikron Danfoss offer a wide range of PIMs. The key advantage is that the internal layout, component matching, and basic thermal interface have already been optimized and validated by the manufacturer. This transforms a complex power stage design problem into a much simpler task of integrating a single, proven component.

Head-to-Head Comparison: PIM vs. Discrete IGBTs

To help you weigh the options, here is a detailed breakdown of how PIMs and discrete solutions stack up across key engineering and business criteria.

Feature	PIM (Power Integrated Module)	Discrete IGBT Solution
Design & Layout Complexity	Low. The complex power stage layout is internal to the module. The designer focuses on connecting the DC bus, AC output, and control signals. Greatly reduces PCB complexity.	High. Requires meticulous PCB layout to manage high currents, minimize parasitic inductance/capacitance, and ensure proper clearance and creepage distances. Very time-consuming.
Assembly & Manufacturing	Simple. A single component to mount onto a heatsink and solder to the PCB. Fewer components reduce assembly time, cost, and potential for errors.	Complex. Multiple power components must be individually placed, soldered, and mounted to heatsinks. Increases assembly steps, process variables, and the risk of manufacturing defects.
Thermal Management	Centralized. All major heat sources are on a single, thermally conductive baseplate (e.g., Al2O3 or AlN DCB). Simplifies heatsink design to a single, flat surface.	Distributed. Heat is generated across multiple components on the PCB. Requires careful PCB thermal design (copper pours, thermal vias) and potentially multiple, smaller heatsinks or complex thermal interfaces.
Power Density	High. The compact, 3D integration within the module allows for a smaller overall power stage footprint compared to a sprawling discrete layout.	Variable. Can be lower due to the required spacing between high-power components on the PCB for thermal and electrical isolation.
Reliability & Parasitics	High & Low. Factory-optimized internal layout leads to low stray inductance, reducing voltage overshoot. As a fully tested unit, it has predictable reliability and Power Cycling Capability data.	Design-Dependent. Reliability is heavily dependent on the quality of the PCB design and assembly. Poor layout can lead to high parasitic inductance, causing voltage ringing, increased losses, and potential device failure.
System Cost	Higher component cost, but lower total system cost (fewer components, simpler PCB, reduced assembly labor, faster time-to-market).	Lower individual component cost, but potentially higher total system cost due to a more complex PCB, longer assembly time, and increased R&D effort.
Sourcing & Supply Chain	Simplified. Procuring a single part number from one supplier for the entire power stage. However, can be a single point of failure if supply is constrained.	Complex. Managing the procurement of numerous individual components from multiple vendors. Offers more flexibility with second-sourcing options for individual parts.
Customization & Performance	Limited. You are constrained by the IGBT/diode technology and topology offered within the module. Best for standard applications.	Unlimited. Total freedom to select the latest generation IGBTs, SiC diodes, and fine-tune the layout for specific performance goals (e.g., ultra-high frequency or efficiency).

Application Deep Dive: Where Does Each Solution Shine?

The best choice is always context-dependent. Let’s explore two common engineering scenarios to illustrate the decision-making process.

When to Choose a Power Integrated Module (PIM)

Application Scenario: Developing a 5.5 kW variable frequency drive (VFD) for industrial pumps and fans.
The Problem: The market is competitive, and speed is paramount. The engineering team is small, and the primary goal is to get a reliable product to market quickly with a compact form factor and minimized manufacturing cost.
The Solution: A PIM is the ideal choice. By selecting a standard 600V or 1200V PIM, the design team bypasses the most challenging part of the power stage design. The layout simplifies to routing control signals and connecting the module’s terminals to the DC link capacitors and output connectors. Assembly consists of mounting one module to one heatsink.
The Result: The development cycle is shortened by weeks, if not months. The risk of layout-induced failures like parasitic turn-on is virtually eliminated. The final product is compact and cost-effective to manufacture, meeting the project’s core business objectives.

When to Opt for a Discrete IGBT Solution

Application Scenario: Designing a high-performance 50 kW string solar inverter.
The Problem: Achieving maximum power conversion efficiency is the single most important design goal. The system operates at a high switching frequency to reduce the size of magnetics, and it may employ a non-standard topology to optimize performance under varying solar conditions. A standard PIM doesn’t offer the required performance or topology.
The Solution: A discrete design is necessary. The engineering team can select the latest generation of low VCE(sat) and low Eoff IGBTs. They might pair them with SiC Schottky diodes to eliminate reverse recovery losses. The PCB layout can be meticulously designed as a multi-layer board with heavy copper to create low-inductance power loops, crucial for minimizing voltage overshoot at high switching speeds.
The Result: The inverter achieves a peak efficiency of >98.5%, a critical competitive differentiator. While the design effort was significantly higher, the discrete approach was the only way to meet the stringent performance targets demanded by the high-end renewable energy market.

Key Engineering Considerations and Trade-offs

Beyond the high-level comparison, several specific engineering challenges are impacted by this choice.

Thermal Management: The Hidden Challenge

Effective Thermal Management is the cornerstone of power electronics reliability. A PIM centralizes the problem. All power semiconductors are mounted on a single Direct Bonded Copper (DBC) substrate, which provides excellent heat spreading and electrical isolation. The engineer’s job is simplified to designing a single, flat heatsink and selecting the right Thermal Interface Material (TIM). With a discrete solution, the challenge is distributed. Each IGBT and diode becomes a separate “hot spot” on the PCB. The designer must use extensive copper planes and an array of thermal vias to pull heat away from the components, and the mechanical design of the heatsink assembly is often more complex.

Parasitic Inductance and EMI Performance

In a discrete design, the physical distance and loop area formed by the connections between the IGBT, the freewheeling diode, and the DC link capacitors create stray inductance. At turn-off, this inductance (L) combined with the rate of change of current (di/dt) generates a voltage spike (V = L * di/dt) across the IGBT. PIMs inherently solve this by placing the IGBT and diode chips in close proximity within the module, resulting in an ultra-low inductance internal layout. This leads to lower voltage overshoots, allowing the system to operate more safely and closer to the IGBT’s voltage rating, and generally results in cleaner switching waveforms and lower EMI emissions.

Conclusion: Making the Right Choice for Your Application

The PIM vs. discrete IGBT debate doesn’t have a single universal winner. It’s a classic engineering trade-off between integration and customization. The right choice hinges on your project’s primary drivers: cost, performance, and time-to-market.

Here’s a simple decision framework:

Is your application a standard topology (e.g., three-phase inverter) under ~30 kW? If yes, a PIM should be your default starting point. The benefits in design speed, reliability, and manufacturing simplicity are immense.
Is maximum performance, a unique topology, or a power level above ~30 kW your primary goal? If yes, the flexibility and component-level optimization of a discrete solution are likely necessary to meet your objectives.
Are your engineering resources or project timelines constrained? If yes, lean heavily towards a PIM. It offloads a significant portion of the high-risk power design effort to the module manufacturer.

Ultimately, Power Integrated Modules represent a powerful tool for accelerating development and reducing system complexity for a vast range of mainstream applications. For those pushing the boundaries of power and efficiency, the control offered by a discrete design remains indispensable. By carefully evaluating your project’s specific needs against the trade-offs discussed here, you can confidently select the strategy that will lead to a successful and competitive product.