Blind Microvia Cleaning with Alkaline Glass-Filler Removal
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Solution Overview
Problem
Existing methods for cleaning nonconductive surfaces of nonconductive layers with glass filler in multilayer printed circuit boards are inefficient, leading to low adhesion of plated copper and copper connections, and are not suitable for semi-additive processing due to health hazards and difficulty in homogeneous application.
Innovation Solution
A method involving a desmear process followed by treatments with a sweller solution, aqueous etching solution, and aqueous reduction solution, followed by an alkaline cleaner solution to remove glass filler, and a drying step to prepare the surface for subsequent metallization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If fluoride etch solutions are used to remove glass filler, then cleaning effectiveness is improved, but health safety deteriorates due to drastic health issues
Solution Approach 1:
The patent converts the harmful fluoride etch solution into a beneficial alkaline cleaner solution that effectively removes glass filler without health hazards. The alkaline solution (pH 10-14) achieves the same cleaning purpose while eliminating the drastic health issues associated with fluoride-based methods.
Solution Approach 2:
The patent changes the chemical parameters of the cleaning solution from fluoride-based to alkaline-based, with pH adjusted to 10-14. This parameter change maintains cleaning effectiveness while eliminating health hazards, as the alkaline environment effectively removes glass filler through different chemical mechanisms.
2Manufacturing precision
If ultrasonic treatment is applied in vertical mode to remove glass filler, then cleaning effectiveness is improved, but ease of operation deteriorates due to difficulty in homogeneous application
Solution Approach 1:
The patent replaces the mechanical ultrasonic vibration system with a chemical cleaning system using alkaline solutions. This substitution eliminates the operational difficulties of applying ultrasonic treatment in vertical mode while achieving homogeneous cleaning through chemical action that naturally reaches all surface areas.
Solution Approach 2:
The patent uses hydraulic circulation of alkaline cleaning solutions to achieve uniform cleaning. The solution flows through the structure, ensuring homogeneous contact with all surfaces including vertical ones, replacing the need for complex mechanical ultrasonic application systems.
3Device complexity
If glass filler is not removed from the surface, then manufacturing complexity is reduced, but reliability deteriorates due to low adhesion of plated copper
Solution Approach 1:
The patent extracts and removes the problematic glass filler from the surface using alkaline cleaning solutions. This extraction eliminates the source of adhesion problems, allowing plated copper to bond directly to the resin matrix without interference from loose or weakly-bounded filler particles.
Solution Approach 2:
The patent performs preliminary removal of glass filler before the plating process. This preliminary action ensures that when copper plating occurs later, there are no loose filler particles to interfere with adhesion, preventing future reliability issues without adding complexity to the plating process itself.
4Manufacturing precision
If desmear processing is performed to remove drilling residues, then manufacturing precision is improved, but productivity deteriorates due to loss of time
Solution Approach 1:
The patent merges the desmear function with the glass filler removal function into a single alkaline cleaning step. The alkaline solution simultaneously removes drilling residues and loose glass filler, achieving the same surface cleanliness as separate desmear and cleaning processes but in one operation, thereby improving productivity.
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
Improves copper adhesion, increases yield rates, and enhances reliability of multilayer assemblies by providing a clean surface for metallization, while reducing hazardous components and energy consumption.
Implementation Method 1
treating the surface with a sweller solution to swell the nonconductive layer
Implementation Method 2
treating the swollen surface with an aqueous etching solution to remove drilling residues
Implementation Method 3
treating the etched surface with an aqueous reduction solution
Implementation Method 4
treating the surface with an alkaline cleaner solution to remove glass filler from the nonconductive surface
Implementation Method 5
drying the surface treated in step (ii) to obtain a dry surface
Data Source
AI summary
The invention relates to a method for cleaning a nonconductive surface of a nonconductive layer, wherein the nonconductive layer is basing on a composite of an organic polymer and the glass filler and comprising a blind micro via (BMV), for manufacturing an article with an integrated circuit, wherein the nonconductive surface comprises a nonconductive wall surface of the BMV, wherein the nonconductive layer is attached to a copper layer and wherein the copper layer forms the bottom of the BMV, wherein the method comprises the steps in the following order: (i) providing the non-conductive surface of the nonconductive layer; (ii) treating the provided surface with a desmear process comprising the following steps in this order: (t1) treatment with a sweller solution comprising water and an organic solvent, (t2) treatment with an aqueous etching solution comprising an oxidation agent, and (t3) treatment with an aqueous reduction solution comprising a reduction agent; (iii) treating the surface treated in step (ii) with an aqueous alkaline cleaner solution in order to remove the glass filler, wherein the aqueous alkaline cleaner solution; and (iv) drying the surface treated in step (iii) in order to get a dry surface, preferably water-free surface; and a use of the method.