Blind Hole Filling in Component Carriers Using Back-Sputtering
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Solution Overview
Problem
Existing methods struggle to efficiently fill blind holes in component carriers with electrically conductive material, particularly when the line space ratio is very small, due to the formation of wedges during desmear processes, leading to poor filling and potential voids.
Innovation Solution
A method involving sputtering and back-sputtering of an electrically conductive filling medium into the blind holes, followed by a back-sputtering process to rearrange the material and fill the wedges, ensuring a homogeneous and void-free filling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If desmear process is used to clean blind holes, then cleaning effectiveness is improved, but wedge formation occurs leading to poor filling
Solution Approach 1:
The patent applies preliminary sputtering deposition before addressing the wedge formation issue. By depositing conductive material in advance, the method creates a base layer that can be subsequently redistributed to fill wedges, turning a potential defect into part of the filling process
Solution Approach 2:
Instead of trying to prevent wedge formation during cleaning, the patent inverts the approach by first allowing wedges to form, then using back-sputtering to remove material from protruding areas and redistribute it into the wedges. This transforms the harmful wedges into fillable depressions
2Quantity of substance
If conventional sputtering is used to fill blind holes, then deposition is achieved, but wedges remain unfilled creating voids
Solution Approach 1:
The patent uses back-sputtering to reverse the deposition process. By applying plasma in reverse, material is removed from areas where it deposited excessively (protruding regions) and redistributed into areas where it should be (wedges and blind hole interiors), achieving homogeneous filling
Solution Approach 2:
The patent changes the sputtering parameters by applying reverse bias voltage after initial deposition. This parameter change transforms the deposition process into a redistribution process, causing material to move from high-concentration areas to low-concentration areas, filling the wedges uniformly
3Area of moving object
If line space ratio is reduced for miniaturization, then component density is improved, but filling reliability deteriorates
Solution Approach 1:
For miniaturized structures with small line space ratios, the patent employs back-sputtering to redistribute material after deposition. This ensures that even in tightly spaced structures where wedge formation is more problematic, the conductive material is properly redistributed to fill all blind holes uniformly without voids
Solution Approach 2:
The patent replaces conventional electroplating or electroless deposition methods with sputtering and back-sputtering. This substitution provides better control over material distribution in high-density, miniaturized structures where traditional wet chemical methods struggle to achieve uniform filling in narrow blind holes
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 improves the filling efficiency of blind holes, even at small line space ratios, providing a reliable and electrically conductive fill without the need for palladium, enhancing the mechanical and electrical reliability of component carriers.
Implementation Method 1
sputtering a filling medium (for example an electrically conductive filling medium) into the blind hole
Implementation Method 2
back-sputtering at least part of the sputtered filling medium so as to at least partially fill the wedges
Data Source
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Figure 7~8
AI summary
A component carrier (100) which comprises a laminated stack (145) comprising at least one electrically conductive layer structure (152, 161) and/or at least one electrically insulating layer structure (102), a blind hole (113) in the stack (145), wherein the blind hole (113) has an exterior tapering section (180) and wedges (182) in a bottom portion, and a filling medium (184), in particular an electrically conductive filling medium (184), filling at least part of the tapering section (180) and the wedges (182).