Stepped Polymer Bond Pad Opening for High-Voltage Wire Bonding
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Solution Overview
Problem
High-voltage electrical isolation is challenging near the contact pads of semiconductor chips, particularly for small bond pad openings, which can lead to deterioration in bond wire quality and package reliability due to capillary contact with polymer layers during wire bonding.
Innovation Solution
A semiconductor package design featuring a polymer layer with a stepped opening structure, where the upper segment is thicker than the lower segment, preventing capillary contact and ensuring reliable wire bonding by using a conductive base attached to the bond pad through insulating and polymer layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick polymer layer is applied around the bond pad opening for high-voltage insulation, then electrical isolation is improved, but the capillary may come into contact with the polymer layer during wire bonding, leading to deterioration in bond wire quality and package reliability
Solution Approach 1:
The polymer layer is divided into two distinct segments: a first segment with a first opening and a second segment with a second opening. This segmentation allows the capillary to pass through the first opening without contacting the polymer layer, while the second segment maintains the necessary electrical insulation thickness, thus resolving the contradiction between reliability and harmful factors.
Solution Approach 2:
Different regions of the polymer layer are given different properties: the first segment has a smaller opening to guide the capillary, while the second segment has a larger opening and sufficient thickness for electrical isolation. This local differentiation allows the structure to simultaneously prevent capillary contact and maintain electrical insulation.
2Reliability
If the bond pad opening is made small to improve electrical isolation, then insulation performance is improved, but wire bonding becomes more difficult and bond wire quality deteriorates
Solution Approach 1:
The polymer layer is segmented into two parts with different opening sizes. The first segment provides a small opening for maintaining electrical isolation, while the second segment provides a larger opening that facilitates wire bonding operations, thus resolving the contradiction between insulation performance and ease of manufacture.
Solution Approach 2:
The solution moves from a two-dimensional planar opening to a three-dimensional stepped structure with multiple levels. The first segment has a smaller opening at one level, while the second segment has a larger opening at another level, allowing both small opening insulation and large opening bonding access to coexist in different spatial dimensions.
3Ease of manufacture
If a uniform polymer layer thickness is used, then manufacturing is simplified, but the capillary cannot be inserted without contacting the polymer layer
Solution Approach 1:
The polymer layer is divided into two segments with different opening characteristics. The first segment has a smaller opening that guides the capillary, while the second segment has a larger opening that allows capillary insertion without contact. This segmentation resolves the contradiction between manufacturing simplicity and operational ease by creating a stepped structure that can be fabricated using standard processes.
Solution Approach 2:
The first segment of the polymer layer is designed with a smaller opening that acts as a preliminary guide structure, directing the capillary into the correct position before it enters the second segment with the larger opening. This preliminary action prevents capillary contact with the polymer layer during insertion while maintaining the overall structural simplicity.
Data Source
Figure 1A~1C
Figure 2A~2B
Figure 3A~3C
AI summary
A semiconductor package comprising a semiconductor die comprising a bond pad (11), an insulating layer (14) covering the bond pad (11), the insulating layer (14) comprising an opening, a polymer layer (13) formed over the insulating layer (14) and covering the sidewalls of the opening in the insulating layer (14), the polymer layer (13) comprising an opening, an electrical conductor (12) comprising a conductive base (12) attached to a part of the bond pad (11) exposed by the insulating layer opening and the polymer layer opening,- the polymer layer (13) comprising an upper segment (13A) and a lower segment (13B) wherein the polymer layer opening is larger in the upper segment (13A) than in the lower segment (13B) .