Adhesive Layer on Redistribution Pads for PoP Bonding Strength
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Solution Overview
Problem
The bonding strength between solder balls and ball pads in Package-on-Package (PoP) semiconductor packages is low, affecting the electrical connectivity and reliability of the devices.
Innovation Solution
Incorporating an adhesive layer made of solder on redistribution pads, which are connected to semiconductor chips using redistribution lines and sealed with an epoxy molding compound, enhancing the bonding strength and electrical connectivity between packages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If solder balls are disposed directly on ball pads, then the structure is simple, but the bonding strength between solder ball and ball pad is low
Solution Approach 1:
An adhesive layer is introduced as an intermediary between the solder ball and the ball pad. This adhesive layer serves as a mediator that enhances the bonding strength and electrical connectivity, resolving the contradiction by providing a stronger interface without requiring fundamental structural changes to the overall package design.
Solution Approach 2:
The bonding interface is transformed from a simple solder-ball-to-pad contact into a composite structure consisting of the adhesive layer combined with solder material. This composite material approach allows optimization of both bonding strength and electrical conductivity, addressing the strength limitation while maintaining structural feasibility.
2Reliability
If adhesive layers are added on redistribution pads, then the bonding strength and electrical connectivity are improved, but the manufacturing process becomes more complex
Solution Approach 1:
The adhesive layer is formed on the redistribution pads during the chip fabrication process before the chip is packaged. This preliminary action allows the adhesive pattern to be precisely defined and positioned, ensuring accurate alignment with the ball pads during subsequent packaging steps, thereby managing the increased manufacturing complexity through advance preparation.
Solution Approach 2:
The formation of the adhesive layer is merged with the existing redistribution layer fabrication process. By combining these steps and using the same photolithography and deposition equipment, the additional complexity is minimized while achieving the desired adhesive pattern alignment with the electrical redistribution 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
The use of adhesive layers on redistribution pads significantly improves the bonding strength and electrical connectivity between semiconductor packages, increasing the reliability and density of electronic devices.
Implementation Method 1
an adhesive layer disposed on a redistribution pad
Data Source
AI summary
A semiconductor package includes a first substrate comprising a plurality of pads arranged in a first side of the first substrate, a plurality of first semiconductor chips stacked on the first side of the first substrate and each first semiconductor chip comprising a plurality of chip pads arranged in a first side of respective first semiconductor chips, and a sealant arranged on the first substrate, the sealant sealing the first semiconductor chips, wherein at least one of the first semiconductor chips comprises a plurality of redistribution pads arranged in the first side of the at least one semiconductor chip, and a plurality of adhesive layers having portions exposed by the sealant, each adhesive layer is disposed on respective redistribution pads.