Equipotential Pad Passivation for Fine-Pitch Solder Bridging

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Solution Overview

Problem

Existing equipotential pad circuits face issues with solder bridging due to continuous metal layers, especially in fine-pitch zones, which can lead to reliability concerns in portable and wearable applications.

Innovation Solution

Incorporating a passivation layer with a thickness of less than 1 μm on the equipotential pad to prevent solder bridging, while maintaining a uniform electrical potential and avoiding an increase in package thickness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a continuous metal layer is used for the equipotential pad, then electrical potential uniformity is maintained, but solder bridging occurs in fine-pitch zones

Engineering Contradiction:

Improvesolder bridging preventionVSAvoidsolder bridging

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent segments the continuous metal layer by introducing a passivation layer that is selectively removed at specific locations to form discontinuous metal regions. This segmentation prevents solder bridging while maintaining electrical connectivity through controlled vias or contacts, directly resolving the solder bridging issue in fine-pitch zones.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The passivation layer acts as an intermediary barrier between the metal layers, preventing direct contact between solder joints. This intermediate layer with controlled thickness and selective removal provides both protection against solder bridging and maintained electrical connectivity where needed.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If a passivation layer is added to prevent solder bridging, then reliability improves, but package thickness increases

Engineering Contradiction:

Improvejoint yieldVSAvoidpackage thickness

Core Design Contradiction:

ReliabilityVSLength of stationary object

Solution Approach 1:

The patent specifies a controlled thickness range for the passivation layer (less than 1 μm, preferably 50-500 nm) to provide adequate protection against solder bridging while minimizing the increase in package thickness. This parameter optimization resolves the contradiction between reliability improvement and thickness control.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The passivation layer is applied with local quality variations - fully present in some areas to prevent solder bridging, and selectively removed in other areas to maintain electrical connectivity. This localized application optimizes both protection and electrical performance while controlling overall thickness.

Inventive Principle:

Principle #3Local quality

3Reliability

If the passivation layer thickness is increased to ensure solder bridging prevention, then reliability improves, but manufacturing complexity increases

Engineering Contradiction:

Improvesolder bridging preventionVSAvoidprocess flow compatibility

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent defines an optimal thickness range (50-500 nm, less than 1 μm) that provides sufficient solder bridging prevention while remaining compatible with existing manufacturing processes. This parameter specification ensures both reliability and ease of manufacture by avoiding excessive thickness that would complicate processing.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The passivation layer is applied as a preliminary step in the manufacturing process, before final assembly and soldering operations. This preliminary application allows for controlled thickness and selective removal patterns to be established early, simplifying subsequent manufacturing steps and ensuring compatibility with existing process flows.

Inventive Principle:

Principle #10Preliminary action

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

The passivation layer effectively inhibits solder bridging, enhances joint yield, and ensures compatibility with current process flows, making it suitable for portable and wearable devices with improved reliability and performance.

Implementation Method 1

Incorporating a passivation layer with a thickness of less than 1 μm on the equipotential pad to prevent solder bridging

Methodology Applied

Scientific EffectElectrical insulation: Dielectric

Implementation Method 2

the equipotential pad may create a pathway for electrical charges to distribute evenly across the surface to which they are applied

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS20250285999A1Interposer module including equipotential pad, package structure including the interposer module and methods of forming the same

Publication Date: 2025.09.11 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

An interposer module includes an interposer, a semiconductor die on the interposer, wherein the semiconductor die includes an equipotential pad and a passivation layer on the equipotential pad, and a plurality of connection structures connecting the equipotential pad to the interposer, wherein the passivation layer is on the equipotential pad between the plurality of connection structures.