Semiconductor Package Substrate With Recessed Solder Ball Standoff
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Solution Overview
Problem
Conventional semiconductor device packaging methods face challenges in reducing height while maintaining reliability, as smaller solder joints are prone to mechanical and thermal failures due to increased susceptibility to cracks and fatigue.
Innovation Solution
The use of substrates with bond pads located on inner conductive layers instead of outermost layers, allowing solder balls to be recessed into the substrate, reducing overall package height and minimizing reliability issues associated with smaller solder joints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If solder joint size is reduced to decrease package height, then package height is reduced, but solder joint reliability deteriorates due to increased susceptibility to mechanical vibrations, thermal shock, and fatigue failure
Solution Approach 1:
The invention moves the bond pad from the outermost surface to an inner layer of the substrate, changing the spatial dimension of the connection point. This allows the solder joint to be recessed into the substrate rather than protruding outward, reducing package height without compromising solder joint size or reliability. The solder joint maintains its full strength while being positioned in a recessed location.
2Ease of manufacture
If bond pad is located on outermost layer to simplify manufacturing, then manufacturing process is simpler, but package height increases due to protruding solder joints
Solution Approach 1:
The bond pad is repositioned from the outermost layer to an inner layer, utilizing the vertical dimension of the multi-layer substrate structure. This dimensional change allows solder joints to be recessed, reducing package height while maintaining manufacturing feasibility through standard multi-layer PCB techniques.
Solution Approach 2:
The bond pad on the inner layer is nested within the substrate structure rather than being exposed on the outer surface. The opening in the outer layer acts as a recess that accommodates the solder joint, creating a nested configuration that reduces overall package height while maintaining connection integrity.
3Reliability
If additional vias are added to connect inner layer bond pads, then electrical connection is achieved, but device complexity increases
Solution Approach 1:
The opening in the outer layer serves multiple functions simultaneously: it provides the recess for the solder joint to reduce package height, and it also serves as the electrical connection pathway from the outer surface to the inner layer bond pad. This multi-functionality eliminates the need for separate via structures, reducing device complexity while maintaining reliable electrical connection.
Data Source
AI summary
A semiconductor device assembly includes a semiconductor die, a substrate carrying the semiconductor die, and a printed circuit board (PCB) coupled to the substrate. The PCB includes a primary conductive layer including a first surface of the substrate and a first solder mask layer coupled to the first surface. The substrate also includes a secondary conductive layer including a second surface of the substrate and a second solder mask layer coupled to the second surface. The substrate further includes an inner conductive layer positioned between the primary layer and the secondary layer, where the inner layer includes a bond pad positioned at the end of an opening that extends from the first solder mask layer through the primary layer to the bond pad of the inner layer. By attaching a solder ball to the bond pad of the inner layer, standoff height is reduced.