Power Module Lid Structure for Pressure Through Soft Potting

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Solution Overview

Problem

Existing electronic power modules face challenges in applying pressure to the top of the circuit carrier, particularly over the power semiconductors, due to the use of soft potting compounds, which restrict design freedom and require planar interconnect techniques or carcinogenic hard potting compounds.

Innovation Solution

A lid is designed to rest on the soft potting compound with a contour-matched outer edge to the wall structure, allowing pressure application over a large area, with optional additional structures to seal gaps and prevent compound leakage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a soft potting compound is used to encase the circuit carrier, then dielectric strength is achieved, but pressure cannot be directly applied to the circuit carrier because the soft compound cannot transmit forces

Engineering Contradiction:

Improvedielectric strengthVSAvoidpressure transmission

Core Design Contradiction:

ReliabilityVSForce

Solution Approach 1:

A rigid lid is introduced as an intermediary element between the pressure application source and the circuit carrier. The lid rests on the soft potting compound and transfers applied pressure to the circuit carrier, overcoming the soft compound's inability to transmit forces while maintaining the dielectric benefits of the soft potting material

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The pressure transmission system is segmented into separate functional components: the soft potting compound maintains dielectric strength and cushions components, while the rigid lid provides the mechanical structure for pressure application and force transmission to the circuit carrier

Inventive Principle:

Principle #1Segmentation

2Strength

If pressure is applied to the top surface of the circuit carrier via spring elements or pressure pieces, then thermal contact with the heat sink is improved, but design freedom is restricted because corresponding areas must be kept clear

Engineering Contradiction:

Improvethermal contactVSAvoiddesign freedom

Core Design Contradiction:

StrengthVSAdaptability or versatility

Solution Approach 1:

The rigid lid serves multiple functions simultaneously: it provides a large-area pressure application surface for thermal contact, acts as a structural cover for the circuit carrier, and allows pressure to be applied over the power semiconductor areas without restricting layout design. This multi-functionality eliminates the need to keep specific areas clear for pressure application

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Force

If a hard potting compound is used instead of soft compound, then pressure can be applied to transfer force to the circuit carrier, but carcinogenic materials must be handled which is problematic

Engineering Contradiction:

Improvepressure transmissionVSAvoidcarcinogenic material handling

Core Design Contradiction:

ForceVSObject-affected harmful factors

Solution Approach 1:

The rigid lid acts as an intermediary that enables pressure transmission without requiring a hard potting compound. The soft potting compound remains in place providing dielectric strength and eliminating carcinogenic material handling, while the lid provides the mechanical structure needed for force transmission to the circuit carrier

Inventive Principle:

Principle #24Intermediary (Mediator)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enables pressure transfer to the circuit carrier and power semiconductors through the soft potting compound, maintaining design freedom and avoiding carcinogenic materials, while ensuring good thermal contact and electrical connectivity.

Implementation Method 1

arranging a lid (21) on the potting compound (20) so that the lid (21) rests fully against the soft potting compound (20)... enables pressure transfer to the circuit carrier and power semiconductors through the soft potting compound

Methodology Applied

Scientific EffectPressure transfer: Pascal's Law

Implementation Method 2

This potting compound is generally necessary to achieve sufficiently high dielectric strength

Methodology Applied

Scientific EffectDielectric strength: Dielectric

Implementation Method 3

heat is generated in the power semiconductors, which must be dissipated... a heat sink or other heat sink is usually arranged on the underside of the circuit carrier and thermally coupled to it

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentEP4686324A1Electronic power module with closure shell covered sealing compound

Publication Date: 2026.01.28 SIEMENS AG

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AI summary

An electronic power module (12) has a circuit carrier (13) with a top (14) and a bottom (15). A structured metal layer (16) is arranged on the top (14) of the circuit carrier (13), on which power semiconductors (17) are arranged, such that the structured metal layer (16) and the power semiconductors (17) form components of an electronic power circuit. The power module (12) has a wall structure (18) with an inner surface (18a) which, together with the top (14) of the circuit carrier (13), forms a trough (19). The circuit carrier (13) is encapsulated within the trough (19) on its top (14) with a soft potting compound (20). A cover (21) is arranged on the potting compound (20) so that the cover (21) rests fully against the soft potting compound (20). An outer edge (22) of the lid (21) is formed with the same contour as an inner edge of the wall structure (18).