Encapsulating Block Local Thickness for Thermal Stress

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Solution Overview

Problem

Electronic devices with integrated-circuit chips experience excessive stress and potential rupture at junctions due to temperature variations, particularly in automotive applications where high-amplitude temperature cycles occur, leading to unreliable electrical connections.

Innovation Solution

The electronic device features a carrier substrate with an encapsulating block that has local zones of smaller thickness in its corners, defined by voids and shoulders, which reduces the overall thickness by 10-50% compared to the surrounding areas, allowing for corner deformation without damaging electrical connections.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the encapsulating block has uniform thickness, then the structural strength is maintained, but excessive stress accumulates at corners during temperature variations causing junction rupture

Engineering Contradiction:

Improveconnection reliabilityVSAvoidencapsulating block strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The encapsulating block features local zones of reduced thickness at corner regions while maintaining full thickness in central areas. This non-uniform thickness distribution allows corner regions to deform more readily during thermal cycling, reducing stress concentration at junctions while preserving structural strength in load-bearing areas.

Inventive Principle:

Principle #3Local quality

2Reliability

If the encapsulating block thickness is reduced at corners, then stress mitigation is achieved, but manufacturing complexity increases

Engineering Contradiction:

Improvestress resistanceVSAvoidencapsulating block structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The reduced thickness zones are pre-formed in the encapsulating block during the molding process using appropriately designed mold cavities. This preliminary shaping eliminates the need for post-manufacturing machining or modification, achieving stress mitigation without significantly increasing manufacturing complexity.

Inventive Principle:

Principle #10Preliminary action

3Adaptability or versatility

If the encapsulating block has smaller thickness in local zones, then corner deformation is enabled to accommodate dimensional variations, but the volume of encapsulating material is reduced

Engineering Contradiction:

Improvethermal expansion accommodationVSAvoidencapsulating block volume

Core Design Contradiction:

Adaptability or versatilityVSVolume of stationary object

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

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

This design mitigates stress and ensures reliable connections by enabling corner deformation to accommodate differential dimensional variations between the device and printed circuit boards, preventing damage or detachment of electrical bonds.

Implementation Method 1

The encapsulating block has, in at least one local zone located in at least one corner and from the front face of the carrier substrate, a smaller thickness than the thickness of this block at least in the surrounding zone... enabling corner deformation without damaging electrical connections

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Data Source

PatentUS10186466B2Electronic device comprising an encapsulating block locally of smaller thickness

Publication Date: 2019.01.22 STMICROELECTRONICS (GRENOBLE 2) SAS

AI summary

An electronic device includes a carrier substrate with at least one integrated-circuit chip mounted on a front face of the carrier substrate. An encapsulation block on the front face and embedding the integrated-circuit chip has a periphery with corners. The encapsulating block further has, in at least one local zone located in at least one corner and from the front face of the carrier substrate, a smaller thickness than a thickness of the encapsulation block at least in a surrounding zone. The electronic device is manufactured by a process in which the zone of smaller thickness is obtained by molding or by machining.