Die Attach Oxide Layer for Lead-Free IC Package Stability
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Solution Overview
Problem
Integrated circuit packages face challenges with die attach materials that have low or no lead content, as they have a lower melting point than the reflow encapsulation temperature, leading to delamination and void formation during processing, which affects mechanical stability and thermal performance.
Innovation Solution
A layer of oxide is formed on the exposed portions of the die attach material to prevent it from flowing into delaminated areas between the encapsulation material and the surface at temperatures above the melting point, using an annealing process to achieve a desired thickness of the oxide layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If lead-free or low-lead die attach material is used, then environmental compliance is improved, but the melting point decreases below reflow encapsulation temperature
Solution Approach 1:
An oxide layer is formed on the die attach material surface before the reflow encapsulation process. This preliminary oxidation creates a protective barrier that prevents the die attach material from melting and flowing into delamination areas when exposed to reflow temperatures exceeding its melting point.
Solution Approach 2:
The oxide layer acts as an intermediary barrier between the die attach material and the encapsulation material. This intermediate layer prevents direct interaction and capillary wicking of molten die attach material into delamination voids during the reflow process.
2Strength
If reflow encapsulation is performed at high temperature, then encapsulation bonding is improved, but die attach material melts and flows into delamination areas
Solution Approach 1:
The die attach material surface is oxidized before encapsulation to create a protective oxide layer. This preliminary action ensures that when high-temperature reflow encapsulation is performed, the oxide layer prevents the die attach material from melting and flowing into delamination areas, maintaining both encapsulation bonding strength and die attach material stability.
Solution Approach 2:
The potential harm of die attach material melting at reflow temperatures is converted into a benefit by deliberately forming an oxide layer that controls the melting behavior. The oxide layer allows the material to undergo controlled oxidation that prevents uncontrolled flow into delamination areas, transforming the melting issue into a protective mechanism.
3Reliability
If die attach material flows into delamination areas, then void formation occurs, but mechanical stability and thermal performance deteriorate
Solution Approach 1:
By forming an oxide layer on the die attach material surface before encapsulation, the patent prevents the die attach material from flowing into delamination areas during reflow processing. This preliminary oxidation action maintains mechanical stability and prevents void formation that would compromise device reliability and thermal performance.
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 oxide layer effectively prevents the die attach material from melting and flowing into voids, maintaining mechanical stability and thermal performance of the semiconductor device even at reflow temperatures, while adhering to environmental regulations by using lead-free or low-lead die attach materials.
Implementation Method 1
a layer of oxide formed on the exposed portions of a die attach material around an electronic die
Implementation Method 2
The melting point of low or no lead die attach materials is often less than the temperature used to reflow encapsulation material
Implementation Method 3
using an annealing process to achieve a desired thickness of the oxide layer
Data Source
AI summary
A method and device are disclosed in which a a lead-free or low-lead die attach material is applied to a surface. An electronic die is positioned on the die attach material. An oxide of at least a specified thickness is formed over an exposed portion of the die attach material. Wire bonds are formed between the electronic die and the surface, and an encapsulant material is applied over the surface, the oxide, and the electronic die.