CSP LED Packaging Recessed Bottom Design

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Solution Overview

Problem

Chip-scale packaging (CSP) LED devices face issues with electrical connection failures and increased thermal resistance due to thermal expansion mismatch between inorganic LED semiconductor dies and organic packaging structures during high-temperature bonding processes, leading to poor bonding quality and reduced efficiency.

Innovation Solution

The CSP LED device features a recessed bottom surface design, where the packaging structure is thermally expanded to deform downward, accommodating its expansion and preventing electrode lift-off from the substrate, ensuring reliable electrical connection and reduced thermal resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a CSP LED device is directly attached onto an application substrate without a lead frame, then material cost is reduced and thermal resistance is lowered, but thermal expansion mismatch during high-temperature bonding causes electrode lift-off and bonding failure

Engineering Contradiction:

Improvematerial costVSAvoidbonding quality

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies preliminary action by pre-forming a recessed space within the packaging structure before the bonding process. This recessed space is specifically designed to accommodate the thermal expansion of the organic packaging material during subsequent high-temperature reflow soldering or eutectic bonding, preventing the electrodes from lifting off the substrate and ensuring reliable bonding without requiring a lead frame

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements beforehand cushioning by creating a recessed cavity in the organic packaging structure that acts as a buffer zone. This cushioning space absorbs the dimensional changes caused by thermal expansion during bonding, protecting the electrode-substrate connection from damage and preventing bonding failures

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Adaptability or versatility

If the packaging structure is made of organic resin material, then manufacturing flexibility is improved, but thermal expansion during high-temperature bonding lifts electrodes off the substrate

Engineering Contradiction:

Improvemanufacturing flexibilityVSAvoiddimensional stability

Core Design Contradiction:

Adaptability or versatilityVSStability of the object's composition

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the physical parameters of the packaging structure by creating a recessed geometry with specific depth and dimensions. This parameter change allows the structure to accommodate thermal expansion while maintaining overall dimensional stability and preventing electrode lift-off during high-temperature bonding processes

Inventive Principle:

Principle #35Parameter changes

3Reliability

If a thick solder bump is added underneath electrodes to accommodate thermal expansion, then electrode lift-off is prevented, but material cost increases and manufacturing yield decreases

Engineering Contradiction:

Improvebonding qualityVSAvoidstructure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts the thermal expansion accommodation function from the bonding interface and relocates it to the packaging structure itself. By forming a recessed space within the organic packaging material, the design eliminates the need for thick solder bumps or other complex compensation structures, simplifying the overall device architecture while maintaining bonding reliability

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces the recessed space as an intermediary element within the packaging structure that mediates between the thermal expansion of the organic material and the bonding requirements. This intermediary recessed cavity absorbs dimensional changes, preventing electrode lift-off without requiring additional complex components or structures

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

This design enhances bonding quality, reduces thermal resistance, and improves the quantum efficiency and reliability of CSP LED devices by maintaining a consistent soldering gap and facilitating effective heat dissipation.

Implementation Method 1

the packaging structure can have considerably larger thermal expansion than the inorganic LED semiconductor die during a high temperature reflow soldering or an eutectic bonding process

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentEP3193379B1Packaging for light emitting device and manufacturing method of the same

Publication Date: 2021.04.14 MAVEN OPTRONICS CO LTD

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AI summary

A chip-scale packaging (CSP) LED device, comprising an LED semiconductor die and a packaging structure, is disclosed. The LED semiconductor die is encapsulated by the packaging structure, wherein the lower surface of the packaging structure has a recessed space underneath. A manufacturing method of the CPS LED device is also disclosed.