Wiring Substrate Cavity Design for Stackable Semiconductor Assembly

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Solution Overview

Problem

Existing wiring substrates for 3D semiconductor assemblies face issues with warpage, thermal expansion mismatches, and solder cracking, leading to unreliable stacking and device failure due to the use of external interconnections and encapsulation methods.

Innovation Solution

A method involving a wiring substrate with a cavity formed by etching a sacrificial metal slug, surrounded by resin compound and metal leads, allowing for vertical interconnection without external interconnections, and enhanced by a resin compound with low thermal expansion and thermal conductivity, and optional re-distribution and build-up circuitries for improved electrical performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If two separated parts are bonded together by adhesive to form stacked substrate, then vertical stacking is achieved, but warpage and thermal expansion mismatch cause dislocation and solder cracking

Engineering Contradiction:

Improvevertical stacking capabilityVSAvoidstructural stability under thermal cycling

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent merges the two separated substrate parts into a single integral substrate with a cavity. The metal leads extend continuously from the first surface through the cavity to the second surface, eliminating the need for bonding two separate parts together. This integration removes the adhesive interface and prevents warpage and thermal expansion mismatch issues.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The resin compound acts as an intermediary material filling the cavity and surrounding the metal leads. It provides mechanical support and thermal management while allowing the metal leads to maintain electrical connectivity through the substrate without requiring external solder joints that are susceptible to cracking.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If solder ball and encapsulation are used to form vertical connection channel, then electrical connection is achieved, but solder deforming and cracking occur after thermal cycling

Engineering Contradiction:

Improveelectrical connectionVSAvoidservice life under thermal cycling

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The patent extracts the solder ball and encapsulation from the vertical connection channel formation process. Instead, metal leads are directly formed extending through the substrate cavity, providing a robust mechanical and electrical connection that does not rely on solder joints susceptible to thermal fatigue and cracking.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Rather than forming vertical channels by adding solder balls on top of the substrate and sealing them, the invention inverts the approach by having metal leads extend from the substrate itself through the cavity. This reverses the conventional method and eliminates the encapsulation layer that can delaminate and crack.

Inventive Principle:

Principle #13The other way round (Inversion)

3Ease of manufacture

If external interconnections and encapsulation are used, then device assembly is achieved, but delamination and I/O disconnection occur

Engineering Contradiction:

Improvedevice assemblyVSAvoidconnection stability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent combines the interconnection function and structural support into the integral substrate with metal leads. The metal leads serve both as electrical conductors and mechanical connectors, eliminating separate encapsulation layers that can delaminate and external interconnection components that may disconnect.

Inventive Principle:

Principle #5Merging (Combining)

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 solution provides a stable mechanical structure that withstands thermal cycling, eliminates solder cracking, and enhances electrical performance by enabling secure vertical stacking and routing without the need for external interconnections, resulting in a reliable and efficient semiconductor assembly.

Implementation Method 1

resin compound with low thermal expansion and thermal conductivity

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

resin compound with low thermal expansion and thermal conductivity

Methodology Applied

Scientific EffectThermal insulation: Thermal Insulation

Implementation Method 3

cavity formed by etching a sacrificial metal slug

Methodology Applied

Scientific EffectEtching:

Data Source

PatentUS10546808B2Methods of making wiring substrate for stackable semiconductor assembly and making stackable semiconductor assembly

Publication Date: 2020.01.28 BRIDGE SEMICON CORP

AI summary

The wiring substrate includes a cavity and a plurality of metal leads disposed around the cavity. The metal leads are bonded with a resin compound and provide horizontal and vertical routing for a semiconductor device to be disposed in the cavity. The resin compound fills in spaces between the metal leads and surrounds the cavity and provides a dielectric platform for a re-distribution layer or a build-up circuitry optionally deposited thereon.