LDS Semiconductor Package Copper Track Vertical Edge Control
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Solution Overview
Problem
Conventional laser direct structuring (LDS) technology faces challenges in achieving fine pitch copper (Cu) tracks with substantially vertical edges, leading to lateral Cu growth and potential short circuits due to isotropic galvanic Cu growth, which limits the application in devices requiring reduced spacing between conductive formations.
Innovation Solution
The method involves using a resist material with laser beam alignment to create trenches or holes in the LDS material, allowing for Cu electroplating with lateral confinement, resulting in Cu formations with substantially vertical edges and preventing lateral growth, thus enabling the formation of Cu tracks with reduced pitch without short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional galvanic Cu growth is used, then Cu formations can be created, but lateral Cu growth occurs causing potential short circuits and preventing fine pitch tracks
Solution Approach 1:
A resist material is introduced as an intermediary substance between the LDS material and the Cu electroplating process. The resist material forms lateral confinement surfaces that act as a physical barrier, preventing Cu from growing laterally while allowing vertical growth. This mediator resolves the contradiction by enabling precise Cu track formation without short circuits.
Solution Approach 2:
The resist material is applied and patterned before the Cu electroplating process. Laser beam energy is used to selectively remove portions of the resist material, creating predefined lateral confinement surfaces. This preliminary structuring ensures that when Cu is deposited, it can only grow in the desired vertical direction within the confined spaces, preventing lateral growth and short circuits.
2Productivity
If Cu track pitch is reduced to meet design constraints, then device density improves, but lateral Cu growth causes short circuits between adjacent tracks
Solution Approach 1:
The resist material serves as a spacer and confinement structure between adjacent Cu tracks. By forming lateral confinement surfaces with the laser beam, the resist material maintains precise spacing between tracks, allowing reduced pitch while preventing Cu from bridging adjacent tracks. This enables higher device density without compromising reliability.
3Manufacturing precision
If laser beam energy is applied to LDS material, then electrically-conductive formations are structured, but without lateral confinement Cu growth becomes uncontrolled
Solution Approach 1:
The resist material acts as a mold or template that guides Cu growth. The laser beam structures the LDS material through the resist, and the resist's lateral walls confine the Cu electroplating process. This intermediary structure simplifies process control by providing physical boundaries that automatically prevent lateral Cu growth, eliminating the need for complex process parameters to control Cu morphology.
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 allows for the fabrication of semiconductor device packages with Cu tracks having substantially vertical edges, reducing the pitch to meet design constraints like 25/25 μm line/space, enhancing the applicability to packages such as QFN, BGA/LGA, and QFP by preventing undesired contact and Cu spikes at corners or vias.
Implementation Method 1
applying laser beam energy to the laser direct structuring material through the resist material formed thereon, wherein said laser beam energy removes portions of said resist material to produce etched-out portions of said resist material
Implementation Method 2
forming electrically-conductive material on said electrically-conductive formations in the laser direct structuring material at said etched-out portions of the resist material
Data Source
AI summary
A method comprises molding laser direct structuring material onto at least one semiconductor die, forming resist material on the laser direct structuring material, producing mutually aligned patterns of electrically-conductive formations in the laser direct structuring material and etched-out portions of the resist material having lateral walls sidewise of said electrically-conductive formations via laser beam energy, and forming electrically-conductive material at said etched-out portions of the resist material, the electrically-conductive material having lateral confinement surfaces at said lateral walls of said etched-out portions of the resist material.