LDS Semiconductor Packaging With Nickel Layer for Cu Via Adhesion
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Solution Overview
Problem
The existing DCI/LDS processes face challenges in semiconductor pad finishing due to limited adhesion between copper vias and underlying pads, often requiring complex and expensive front-end process steps like sputtering for seed layer deposition.
Innovation Solution
Incorporating a nickel electroless plating step before copper electroless plating to enhance adhesion, with an optional zincate process for improved adhesion, allowing for copper vias to be formed on non-copper pad finishes like NiPd or Al without additional machining or process changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sputtering is used to deposit a seed layer to facilitate adhesion between Cu vias and underlying pad, then adhesion is improved, but process complexity and cost increase
Solution Approach 1:
The patent introduces an intermediary layer (such as a nickel layer or zincate layer) between the copper via and the underlying pad to facilitate adhesion. This intermediary layer acts as a mediator that chemically or physically bonds to both surfaces, resolving the adhesion problem without requiring complex sputtering processes.
Solution Approach 2:
The patent changes the chemical or physical parameters of the pad surface or the via material to improve adhesion. For example, it may involve modifying the surface chemistry of the pad or changing the plating conditions to enhance bonding between layers, thereby achieving good adhesion through parameter optimization rather than complex process steps.
2Ease of manufacture
If copper electroless plating is applied directly on non-copper pad finishes, then process simplicity is maintained, but adhesion is insufficient
Solution Approach 1:
The patent applies an intermediary layer (such as electroless nickel plating or zincate treatment) between the non-copper pad finish and the copper electroless plating. This intermediary layer provides a bonding interface that ensures adequate adhesion while maintaining the overall simplicity of the electroless plating process and avoiding complex front-end modifications.
3Reliability
If additional front-end process steps are implemented to improve adhesion, then adhesion is improved, but manufacturing cost increases
Solution Approach 1:
The patent introduces cost-effective intermediary layers such as electroless nickel plating or zincate treatment that provide the necessary adhesion at a lower cost compared to complex front-end processes like sputtering. These intermediaries are applied through relatively simple and economical processes.
Solution Approach 2:
The patent optimizes plating parameters such as solution composition, temperature, and deposition conditions to achieve good adhesion through parameter control rather than additional expensive process steps. This approach maintains manufacturing cost-effectiveness while ensuring reliable adhesion.
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 approach enables flexible metal finishing options, improves current distribution, facilitates integration of passive components, and reduces unit costs by simplifying the backend process, while maintaining effective thermal dissipation and packaging flexibility.
Implementation Method 1
Incorporating a nickel electroless plating step before copper electroless plating to enhance adhesion
Implementation Method 2
copper electroless plating to enhance adhesion, with an optional zincate process for improved adhesion, allowing for copper vias to be formed
Data Source
AI summary
A semiconductor die is attached on a die-attachment portion of a substrate such as a leadframe. The semiconductor die has a front surface opposite the substrate and one or more contact pads at the front surface having an outer surface finishing of a first electrically conductive material such as NiPd or Al. An encapsulation of laser direct structuring, LDS material is molded onto the semiconductor die attached on the substrate. Laser beam energy is applied to selected locations of the front surface of the encapsulation of LDS material to activate the LDS material at the selected locations and structure therein electrically conductive formations comprising one or more vias towards the contact pad. The vias comprise a second electrically conductive material that is different from the first electrically conductive material of the outer surface finishing of the contact pad. Prior to growing the second electrically conductive material a nickel layer is formed over the outer surface finishing of the contact pad, wherein the nickel layer promotes adhesion between the second electrically conductive material and the first electrically conductive material.