Bonding Wire Kink Design for Thermal Stress Relief

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Solution Overview

Problem

Light-emitting device packages face reliability issues due to stress-induced breakage of bonding wires caused by thermal expansion differences between the wire and encapsulation layer, leading to repeated separation from electrodes and terminals.

Innovation Solution

Incorporating kink portions in the bonding wire that absorb compressive and expansion stresses by bending inwardly within the wire loop, reducing the risk of breakage and maintaining connections under thermal cycling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a bonding wire is used to electrically connect the light-emitting device chip and terminal portion, then electrical connectivity is achieved, but the wire is prone to breakage due to thermal expansion differences between the wire and encapsulation layer

Engineering Contradiction:

Improvebonding wire durabilityVSAvoidthermal stress-induced breakage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A kink portion is pre-formed in the bonding wire at a specified position between the light-emitting device chip and terminal portion. This kink portion acts as a stress-absorbing element that compensates for thermal expansion differences between the wire and encapsulation layer before breakage occurs, thereby preventing wire fracture under thermal cycling conditions

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The bonding wire's structural parameter is modified by introducing a kink portion with specific geometric characteristics (position, curvature radius, angle). This parameter change enables the wire to flexibly accommodate thermal stresses without breaking, transforming the wire from a rigid conductor to a stress-resilient connection element

Inventive Principle:

Principle #35Parameter changes

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 kink portions effectively absorb thermal stresses, reducing the likelihood of bonding wire breakage and maintaining electrical connections, thereby enhancing the reliability of light-emitting device packages.

Implementation Method 1

thermal expansion differences between the wire and encapsulation layer

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

kink portions in the bonding wire that absorb compressive and expansion stresses by bending inwardly within the wire loop

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Data Source

PatentEP2475018B1Light-emitting device package and method of manufacturing the same

Publication Date: 2019.12.25 SAMSUNG ELECTRONICS CO LTD

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Figure 5~6

AI summary

A light-emitting device package includes: a package body (2) on which a mount portion (210) and a terminal portion (220) are disposed; a light-emitting device chip (300) that is mounted on the mount portion; and a bonding wire (401) that electrically connects an electrode of the light-emitting device chip and the terminal portion. The bonding wire includes a rising portion (410) that rises from the light-emitting device chip to a loop peak (412), and an extended portion (440) that connects the loop peak and the terminal portion. A first kink portion (413), which is bent in a direction intersecting a direction in which the rising portion rises, is disposed on the rising portion (410).