Printed Wiring Board with Embedded Recessed Pads
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Solution Overview
Problem
Existing printed wiring boards without core substrates face challenges in maintaining flatness and preventing short-circuit defects during semiconductor element mounting, particularly when connection pads are formed at fine pitches, due to warping and lack of insulating material between pads.
Innovation Solution
A printed wiring board design featuring a laminate with alternately laminated conductor and resin insulating layers, where second conductor pads are embedded in the resin insulating layer with surfaces recessed from the second surface, and a support plate is positioned via a solder resist layer to suppress warpage and short-circuit defects, allowing for fine-pitch pad formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If connection pads are formed at fine pitches on a multilayer wiring board without core substrate, then the board complexity is reduced and manufacturing is simplified, but warping occurs and short-circuit defects increase during semiconductor element mounting
Solution Approach 1:
The patent uses a composite structure combining a resin insulating layer with a support plate having higher rigidity. The support plate is made of a material different from the resin insulating layer, creating a composite construction that maintains structural stability without requiring a core substrate. This composite approach prevents warping while keeping the overall board structure relatively simple.
Solution Approach 2:
The support plate is strategically positioned at the back surface of the insulating layer where mechanical support is most needed. The conductor pads are embedded only in specific regions where electrical connection is required, while the support plate provides localized rigidity enhancement. This local quality approach addresses warping and short-circuit prevention without adding unnecessary complexity throughout the entire board structure.
2Area of moving object
If connection pads are formed at fine pitches, then the wiring density is increased and device integration is improved, but solder spread between pads causes short-circuit defects
Solution Approach 1:
The resin insulating layer serves as an intermediary material between adjacent conductor pads at fine pitches. This insulating layer prevents solder from spreading between closely spaced pads during the mounting process, eliminating short-circuit defects while allowing high wiring density. The support plate further reinforces this isolation by providing a rigid backing that maintains precise pad positioning.
Solution Approach 2:
The support plate provides preemptive mechanical support to the fine-pitch conductor pad structure before soldering occurs. By establishing rigid structural support in advance, the system prevents solder bridging and short-circuits before they can happen during the mounting process, rather than attempting to correct issues after they occur.
3Stability of the object's composition
If a support plate is added to maintain flatness, then warping is suppressed and mounting stability is improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The support plate serves multiple functions simultaneously: it provides mechanical support to prevent warping, offers a mounting surface for the insulating layer, and acts as a barrier to prevent solder penetration from the back side. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in overall device complexity despite adding structural support.
4Reliability
If conductor pads are embedded in the insulating layer with recessed surfaces, then short-circuit prevention is enhanced and solder containment is improved, but manufacturing precision requirements increase
Solution Approach 1:
The conductor pads are formed and embedded in the resin insulating layer before the support plate is attached. This preliminary embedding action ensures precise pad positioning and proper insulation establishment prior to adding the rigid support structure. By completing the precision-critical embedding step first, the subsequent support plate attachment becomes a simpler, less precision-sensitive operation.
Data Source
AI summary
A printed wiring board includes a support plate, a laminate formed on the support plate and including first conductor pads on a first surface side of the laminate and second conductor pads on a second surface side of the laminate, and a solder resist layer interposed between the support plate and the laminate and having openings formed such that the openings are exposing the first conductor pads respectively. The laminate includes a resin insulating layer and has a first surface on the first surface side and a second surface on the second surface side on the opposite side with respect to the first surface of the laminate, the second conductor pads are embedded in the second surface of the laminate such that the second conductor pads have surfaces recessed from the second surface of the laminate respectively.