Semiconductor Wire Bonding Anchor Studs Prevent Delamination
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Solution Overview
Problem
Semiconductor devices with plastic packages are prone to delamination and cracking due to moisture-induced expansive pressures, which existing methods have only partially addressed, especially as devices miniaturize and time-to-market pressures increase, making it challenging to maintain reliability and adhesion.
Innovation Solution
The implementation of mechanical anchor studs created through wire bonding technology, including ball bonds and stitch bonds with wire arches, which provide additional surface area for adhesion and act as mechanical obstacles to prevent delamination between the package and the encapsulated device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the area for adhesion between package material and device components is increased, then delamination resistance is improved, but device size increases
Solution Approach 1:
The patent transitions from two-dimensional planar adhesion to three-dimensional vertical adhesion by creating stacked ball bonds that extend perpendicular to the leadframe surface. This dimensional change allows adhesion area to increase without increasing the device footprint, as the additional bonding surface is achieved through vertical stacking rather than lateral expansion.
Solution Approach 2:
The patent divides the adhesion function into multiple discrete ball bonds stacked vertically, rather than relying on a single large bonding area. Each ball bond acts as an independent adhesion element, and their cumulative effect provides superior delamination resistance while maintaining a compact overall structure.
2Reliability
If wire bonding is used to create mechanical anchor studs, then delamination prevention is improved, but manufacturing complexity increases
Solution Approach 1:
The wire bonding process performs multiple functions simultaneously: it creates electrical connections and forms mechanical anchor studs for delamination prevention. This multi-functionality eliminates the need for separate adhesion-enhancement processes, reducing overall manufacturing complexity despite the added structural feature.
Solution Approach 2:
The patent merges the electrical interconnection function with the mechanical anchoring function into a single wire bonding operation. The same wire bonds that carry electrical signals also serve as mechanical anchors, combining two critical functions into one integrated structure and process step.
3Reliability
If existing adhesion enhancement methods are applied, then some delamination resistance is achieved, but effectiveness is limited and partial
Solution Approach 1:
The patent creates a composite adhesion structure combining metal wire bonds with polymeric molding compound. This composite approach leverages the strength and adhesion properties of both materials, creating a more effective delamination barrier than either material alone could provide.
Solution Approach 2:
The patent utilizes the spherical geometry of ball bonds to maximize adhesion effectiveness. The curved surface of each ball bond provides optimal contact area with the molding compound and leadframe, enhancing mechanical interlocking and adhesion strength compared to flat or angular bonding structures.
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 method effectively prevents delamination in highly accelerated stress tests at elevated temperatures and humidity, ensuring the reliability and longevity of semiconductor devices by creating strong mechanical barriers that withstand thermal and moisture-related stresses.
Implementation Method 1
Based on the strength of diffusion bonds, a plurality of mechanical anchor studs are created in quick sequence
Data Source
AI summary
A semiconductor device (100) comprising a leadframe with a pad (101) and elongated leads (103) made of a base metal plated with a layer enabling metal-to-metal bonding; a semiconductor chip (110) attached to the pad, the chip having terminals. A metallic wire connection (130) from a terminal to a respective lead, the connection including a first ball bond by a first squashed ball (131) attached to the terminal, and a first stitch bond (132) attached to the lead. A second squashed ball (150) of the wire metal attached to the lead as a second ball bond adjacent to the first stitch bond (132). A package (170) of a polymeric compound encapsulating the chip, wire connection, second ball and at least a portion of the elongated lead, the compound adhering to the materials of the encapsulated entities.