Stacked Semiconductor Package Without DAF for Stable Wire Bonding
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Solution Overview
Problem
The use of die attach films (DAF) between semiconductor chips leads to increased thickness and thermal expansion issues, which can cause peeling or separation of chips, hindering miniaturization and stability in semiconductor packages.
Innovation Solution
A semiconductor package design that eliminates the use of DAF by direct contact between semiconductor chips through a protection layer with recessed portions exposing bonding pads, allowing for stable wire bonding without intermediate adhesives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a die attach film (DAF) is used between semiconductor chips, then the chips can be bonded together, but the package thickness increases and thermal expansion causes peeling or separation
Solution Approach 1:
The patent removes the die attach film from the chip stacking structure, allowing chips to be directly bonded to each other. This extraction of the intermediate layer eliminates the thickness contribution of the DAF and removes the source of thermal expansion mismatch, thereby resolving both the thickness increase and peeling issues while maintaining bonding strength through direct chip-to-chip contact
Solution Approach 2:
The patent merges the bonding function directly between adjacent chip surfaces by eliminating the intermediate die attach film. The first chip, second chip, and third chip are stacked in direct contact, with wiring structures providing both electrical connection and mechanical bonding, thereby combining multiple functions into a unified direct-bond structure that reduces overall thickness
2Strength
If a die attach film (DAF) is used between semiconductor chips, then the chips can be bonded together, but thermal expansion causes peeling or separation
Solution Approach 1:
The patent extracts and removes the die attach film that causes thermal expansion mismatch. By eliminating this intermediate layer with different thermal properties, the patent prevents the peeling and separation issues that occur during thermal cycling, thereby maintaining bonding strength while significantly improving chip stability and reliability
Solution Approach 2:
The patent achieves homogeneity in thermal expansion characteristics by allowing direct contact between identical semiconductor chip materials. Since adjacent chips have matching thermal expansion coefficients, the structure expands uniformly during heating, preventing the differential expansion that causes peeling at the DAF-chip interfaces
3Ease of manufacture
If the bonding pad is completely exposed, then wire bonding is easier, but the protection is reduced
Solution Approach 1:
The patent applies local quality by selectively exposing only the bonding pad region through the protection layer while keeping the rest of the chip surface covered. This localized exposure provides sufficient access for wire bonding operations while maintaining protective coverage over the active device areas, thereby achieving both manufacturing ease and reliability
Solution Approach 2:
The protection layer serves as an intermediary element that partially covers the bonding pad. It provides a barrier against contamination and damage while allowing wire bonding access through the exposed region. This intermediary structure reconciles the conflicting requirements of protection and accessibility
Data Source
AI summary
A semiconductor package including a first semiconductor chip, which includes a first semiconductor board, a bonding pad on the first semiconductor board, and a protection layer covering an upper surface of the first semiconductor board and including a recessed region exposing at least a portion of an upper surface of the bonding pad therethrough, a second semiconductor chip including a second semiconductor board in direct contact with the protection layer, and a wire electrically connecting the first semiconductor chip and the second semiconductor chip and connected to the bonding pad may be provided.