Package on Package Structure with Non-Solder Ball and Intermediate Layer

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Solution Overview

Problem

The semiconductor industry faces challenges in manufacturing package on package (PoP) technologies due to the large pitch and thin isolation regions between connectors, which can lead to shorting and design limitations, especially with the use of laser-drilled through molding vias.

Innovation Solution

The use of non-solder metal balls with a solder coating layer and an intermediate layer to prevent intermetallic compound formation, allowing for more precise bonding and reduced risk of shorting, along with a molding underfill to support the structure and manage thermal expansion mismatches.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If laser-drilled through molding vias are used to form connectors, then manufacturing process is simplified, but pitch is large and isolation regions are thin leading to shorting risk

Engineering Contradiction:

Improveconnector formation processVSAvoidconnector shorting risk

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

An intermediate layer is introduced between the solder coating layer and the non-solder metal ball to prevent direct contact and intermetallic compound formation. This intermediary layer acts as a barrier that eliminates the shorting risk while allowing the laser-drilled via process to continue

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The connector structure uses a composite material system consisting of non-solder metal ball core, intermediate layer, and solder coating layer. This composite structure combines the benefits of different materials: the non-solder metal ball provides structural integrity, the intermediate layer prevents intermetallic formation, and the solder coating enables bonding

Inventive Principle:

Principle #40Composite materials

2Area of stationary object

If connector pitch is reduced to increase integration density, then area utilization improves, but risk of bridging and disconnection increases

Engineering Contradiction:

Improvepackage area utilizationVSAvoidconnector bridging risk

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

The intermediate layer serves as a protective barrier between adjacent connectors, preventing bridging when pitch is reduced. This mediator layer maintains electrical isolation even when connectors are placed closer together, enabling higher integration density without sacrificing reliability

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The connector structure has varying local properties: the intermediate layer provides electrical isolation where needed, while the solder coating provides bonding capability at the connection interface. This local differentiation of properties allows reduced pitch while maintaining both reliability and connectivity

Inventive Principle:

Principle #3Local quality

3Device complexity

If thin isolation regions are used between connectors, then manufacturing complexity is reduced, but thermal isolation is insufficient leading to thermal expansion mismatches

Engineering Contradiction:

Improveisolation region structureVSAvoidthermal isolation performance

Core Design Contradiction:

Device complexityVSTemperature

Solution Approach 1:

The multi-layer composite structure (intermediate layer + solder coating layer) provides both mechanical isolation and thermal management. The different material layers have different thermal expansion coefficients that compensate for thermal mismatches, maintaining structural integrity under thermal stress without requiring complex thick isolation regions

Inventive Principle:

Principle #40Composite materials

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 approach enables smaller pitch connectors with controlled height, reduced risk of bridging or disconnection, and improved thermal isolation, enhancing the reliability and integration density of PoP structures.

Implementation Method 1

a solder coating layer over a surface of the non-solder material

Methodology Applied

Scientific EffectSoldering: Soldering

Implementation Method 2

an intermediate layer between the solder layer and the non-solder material

Methodology Applied

Scientific EffectDiffusion barrier: Diffusion Barrier

Implementation Method 3

a molding underfill to support the structure and manage thermal expansion mismatches

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS11264342B2Package on package structure and method for forming the same

Publication Date: 2022.03.01 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

Some embodiments relate to a semiconductor device package, which includes a substrate with a contact pad. A non-solder ball is coupled to the contact pad at a contact pad interface surface. A layer of solder is disposed over an outer surface of the non-solder ball, and has an inner surface and an outer surface which are generally concentric with the outer surface of the non-solder ball. An intermediate layer separates the non-solder ball and the layer of solder. The intermediate layer is distinct in composition from both the non-solder ball and the layer of solder. Sidewalls of the layer of solder are curved or sphere-like and terminate at a planar surface, which is disposed at a maximum height of the layer of solder as measured from the contact pad interface surface.