Semiconductor Bond Pad Sealing via Shielding Layer Aperture
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Solution Overview
Problem
The packaging of semiconductor devices is challenged by corrosion due to the galvanic reaction between chloride ions and alloys formed from different materials used for bond pads and bonding wires, which affects the reliability of interconnections.
Innovation Solution
A method involving a shielding layer with an aperture over a bond pad, where a deformable ball from a bond wire is bonded to the pad, filling the aperture and sealing it, preventing exposure to molding compounds and thus protecting the interconnection from corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the bond pad is fully exposed for bonding, then the bonding process is simplified, but the bond pad is exposed to molding compounds and chloride ions causing corrosion
Solution Approach 1:
The shielding layer is applied selectively to cover only the peripheral region surrounding the bond pad, leaving the central bonding area exposed. This local differentiation allows the bond pad to remain accessible for bonding while protecting the vulnerable alloy interface from corrosion, resolving the contradiction between manufacturing simplicity and reliability
Solution Approach 2:
A shielding layer made of corrosion-resistant material (such as nickel or palladium) is introduced as an intermediary barrier between the molding compound/chloride ions and the alloy interface. This intermediate layer prevents direct contact between corrosive elements and the vulnerable bond pad-wire interface, thereby protecting against corrosion without interfering with the bonding process
2Reliability
If a shielding layer is added to protect the bond pad, then corrosion resistance is improved, but the device structure becomes more complex
Solution Approach 1:
Instead of applying a shielding layer across the entire bond pad surface, the invention selectively applies the shielding layer only to the peripheral region surrounding the bond pad. This localized approach provides necessary corrosion protection while minimizing the addition of structural complexity to the device
3Reliability
If the aperture is completely filled with the bond wire ball, then sealing effectiveness is improved, but the bonding process becomes more difficult
Solution Approach 1:
The shielding layer with a pre-formed aperture is prepared in advance, with the aperture size carefully designed to be slightly larger than the bond wire ball. This preliminary preparation ensures that the bond wire ball can easily pass through and fill the aperture during bonding, achieving complete sealing without requiring excessive bonding force or complex bonding processes
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 solution effectively seals the bond pad from corrosion by ensuring the molding compound does not contact the alloy interface, enhancing the reliability and longevity of the semiconductor device's interconnections.
Implementation Method 1
sealing the part of the bond pad exposed by the aperture of the shielding layer by deforming the ball of the bond wire to fill the aperture of the shielding layer
Implementation Method 2
The bond pads on the device die and the wires are usually made from different materials, and the bonding makes use of alloys formed from the different materials
Implementation Method 3
Particular components, for example chloride ions (chloridion), chemically react with the alloys due to galvanic effect, which can result in corrosion
Data Source
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AI summary
A method of packaging a semiconductor device includes: bonding a ball (304) at an end of a bond wire (302) to a bond pad (204) of a semiconductor device die (200) in an aperture of a shielding layer (206) of the semiconductor device; and sealing the part of the bond pad (204) exposed by the aperture of the shielding layer (206) by deforming the ball (304) of the bond wire (302) to fill the aperture of the shielding layer (206). The aperture of the shielding layer (206) includes an edge wall, and exposes a part of the bond pad (204). The shielding layer (206) covers a remaining part of the bond pad (204). The aperture of the shielding layer (206) is completely filled with the ball (304) of the bond wire (302), thereby deforming the edge wall of the shielding layer (206).