Die Extraction via Flattening and Selective Polishing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing die extraction methods for integrated circuit packaging structures fail to accurately locate failure points in lower-layer dies due to die cracking and corrosion, especially when attempting to maintain the original electrical properties and structural integrity of ultra-thin stacked dies.
Innovation Solution
A die extraction method involving the removal of solder balls, flattening, and selective polishing to retain die attach film layers and bonding wires, followed by short-term acid-base treatment to extract the target die while preserving its electrical properties and structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple stacked dies are separated by soaking with high-temperature fuming nitric acid for a long time, then the dies can be extracted from the stack, but die cracking and die pad corrosion occur due to the ultra-thin thickness of the stacked dies
Solution Approach 1:
The patent applies preliminary flattening to the sample before acid soaking. The flattening process pre-compresses and stabilizes the ultra-thin die structure, making it more resistant to cracking and corrosion during subsequent acid treatment. This preliminary mechanical preparation enables the use of acid soaking without causing the harmful effects that would otherwise occur.
Solution Approach 2:
The patent changes the physical state and mechanical properties of the die stack through flattening compression, transforming the ultra-thin die structure into a more robust configuration that can withstand the chemical treatment. By altering the mechanical parameters (compression, density) before chemical exposure, the die integrity is preserved during extraction.
2Loss of time
If traditional hand-held polishing is used to polish the sample to the target die to reduce soaking time, then the soaking time is reduced, but a large step difference (about 30 μm or more) is created on the surface of the sample
Solution Approach 1:
The patent replaces traditional hand-held mechanical polishing with a flattening compression system. Instead of removing material through abrasion, the flattening process uses controlled compression to level the surface, achieving both time reduction and surface flatness preservation without the step differences caused by conventional polishing.
3Measurement precision
If the original electrical properties of the die at the lower layer are kept unchanged during extraction, then accurate failure location can be carried out, but the extraction process becomes more complex and time-consuming
Solution Approach 1:
The flattening process is performed as a preliminary step before acid soaking, preparing the die structure in advance to maintain electrical properties during extraction. This pre-preparation eliminates the need for complex post-extraction repairs or modifications, simplifying the overall process while ensuring measurement accuracy.
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
Enables accurate failure point location and extraction of target dies with minimal structural damage and electrical property alteration, facilitating effective inspection and reducing the risk of die cracking and corrosion.
Implementation Method 1
flattening the sample and the polishing jig by a flattener
Implementation Method 2
polishing a front side of the sample to remove a part on a front side of the target die
Implementation Method 3
soaking with high-temperature fuming nitric acid
Data Source
AI summary
Provided is a die extraction method, comprising the following steps: removing solder balls; polishing a front side of the sample to remove a part on a front side of the target die, and retain a part of a die attach film (DAF) layer on the front side of the target die and a bonding wire located in the part; attaching the front side of the sample to the polishing jig and flattening the sample and the polishing jig by the flattener; polishing the back side of the sample to remove a part on a back side of the target die, and retain a DAF layer on the back side of the target die; removing the DAF and a packaging material remaining on the sample to obtain the target die; and attaching the back side of the target die to a glass slide, thus completing extraction of the target die.