Wiring Substrate Pad Layout to Prevent Via Haloing
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Solution Overview
Problem
Existing wiring substrates face issues with haloing, where the outer insulating layer peels off from conductor pads due to excessive desmear treatment, particularly affecting smaller conductor pads, leading to structural integrity concerns.
Innovation Solution
The design incorporates first and second conductor pads with different annular widths and haloing amounts, along with specific via hole diameters and inter-pad distances, and employs tailored desmear treatments to minimize resin residue removal time, ensuring balanced processing for both types of via holes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If desmear treatment is applied to remove resin residues from via holes, then manufacturing cleanliness is improved, but the insulating layer peels off from conductor pads causing haloing
Solution Approach 1:
The patent applies different desmear treatment conditions to different via hole types. First via holes (with larger annular widths) receive standard desmear treatment, while second via holes (with smaller annular widths) receive reduced or no desmear treatment. This local differentiation prevents excessive peeling of the insulating layer from conductor pads in areas where the annular width is small, thereby preventing haloing while maintaining via hole cleanliness where appropriate.
Solution Approach 2:
The patent changes the desmear treatment parameters based on the annular width of conductor pads. By adjusting the degree and duration of desmear treatment according to the specific geometry of each via hole type, the process optimizes the balance between removing resin residues and preserving the adhesion between the insulating layer and conductor pads.
2Ease of manufacture
If uniform desmear treatment is applied to all via holes, then processing simplicity is maintained, but smaller conductor pads suffer excessive peeling and haloing
Solution Approach 1:
The patent implements localized quality control by differentiating desmear treatment based on via hole type. First via holes with larger annular widths undergo standard desmear treatment for complete resin removal, while second via holes with smaller annular widths receive reduced treatment to prevent insulating layer peeling. This approach maintains reliability for smaller pads while preserving manufacturing efficiency through a systematic differentiation strategy.
3Area of stationary object
If the annular width of conductor pads is reduced to increase density, then area utilization is improved, but susceptibility to haloing increases
Solution Approach 1:
The patent addresses the increased haloing susceptibility of smaller conductor pads by applying reduced or selective desmear treatment specifically to second via holes associated with these pads. This local adjustment compensates for the reduced annular width, preventing excessive peeling of the insulating layer while allowing high-density layout with smaller pads to be implemented.
Data Source
AI summary
A wiring substrate includes first conductor pads formed on a surface of an insulating layer, second conductor pads formed on the surface of the insulating layer, a second insulating layer covering the surface of the insulating layer and first and second conductor pads, first via conductors formed in first via holes penetrating through the second insulating layer such that the first via conductors are formed on the first conductor pads, and second via conductors formed in second via holes penetrating through the second insulating layer such that the second via conductors are formed on the second conductor pads. The first and second conductor pads are formed such that an annular width amount of each second conductor pad is smaller than an annular width amount of each first conductor pad and that a haloing amount in each second conductor pad is smaller than a haloing amount in each first conductor pad.