Wiring Substrate Adhesion Insulating Layer Roughening
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Solution Overview
Problem
The manufacturing process of coreless type wiring substrates results in the lowermost resin layer having a longer heating history, leading to insufficient roughening and adhesion issues when forming wiring layers on its exposed face, which limits design flexibility and increases the risk of bulges during electroless plating.
Innovation Solution
The introduction of an adhesion insulating layer on the exposed face of the lowermost resin layer, which is roughened to match the surface roughness of other resin layers, allowing for improved adhesion and preventing bulges by using a semi-additive method with electroless plating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the lowermost resin layer is repeatedly subjected to heating process during manufacturing, then the resin layer is firmly cured, but the surface cannot be adequately roughened and adhesion of wiring layer is insufficient
Solution Approach 1:
The patent divides the single lowermost resin layer into two separate layers: a first resin layer (original lowermost layer) and a second resin layer (newly added layer). The first resin layer retains its firmly cured property from repeated heating, while the second resin layer provides a fresh surface that can be adequately roughened for wiring layer adhesion. This segmentation allows both requirements to be satisfied simultaneously.
Solution Approach 2:
The patent applies preliminary roughening treatment to the surface of the first resin layer before forming the second resin layer. This preliminary action creates a roughened surface that enhances adhesion for the second resin layer, and subsequently the second resin layer's surface is roughened before wiring layer formation. This sequential preliminary roughening ensures adequate adhesion at both interfaces.
2Ease of manufacture
If wiring layer is formed on the exposed face of lowermost resin layer, then wiring connections are established, but sufficient adhesion cannot be obtained due to inadequate surface roughness
Solution Approach 1:
The patent segments the resin structure into two layers, allowing the wiring layer to be formed on the second resin layer's surface which has been freshly roughened. This ensures adequate adhesion strength between the wiring layer and resin surface, while the first resin layer maintains its cured structural integrity.
Solution Approach 2:
The second resin layer acts as an intermediary between the firmly cured first resin layer and the wiring layer. It provides a fresh, roughenable surface that mediates the adhesion requirement, while the first resin layer mediates the structural support and curing firmness requirement.
3Adaptability or versatility
If narrow pitches are formed without adequate surface roughness, then design flexibility is limited, but bulges occur during electroless plating
Solution Approach 1:
By segmenting the resin into two layers with both surfaces roughened, the patent enables narrow pitch wiring patterns to be formed on the second resin layer's surface with adequate adhesion. This prevents plating bulges during electroless plating while maintaining design flexibility for narrow pitches, as the fresh surface provides proper anchoring for the wiring layer.
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 ensures sufficient adhesion of wiring layers across all build-up layers, enabling the formation of narrow pitches without design limitations, as all layers are adequately roughened and adhere well, facilitating the formation of fine wiring patterns.
Implementation Method 1
an outer face of the adhesion insulating layer is made to a roughened face
Implementation Method 2
using a semi-additive method with electroless plating
Data Source
AI summary
A wiring substrate includes a first insulating layer, an adhesion insulating layer formed under the first insulating layer and an outer face of the adhesion insulating layer is made to a roughened face, a first wiring layer formed on the first insulating layer, a second insulating layer formed on the first insulating layer, and in which a first via hole reaching the first wiring layer is provided, a second wiring layer formed on the second insulating layer, and connected to the first wiring layer through the first via hole, a second via hole formed in the adhesion insulating layer and the first insulating layer, and reaching the first wiring layer, and a third wiring layer formed on the outer face of the adhesion insulating layer, and connected to the first wiring layer through the second via hole.