Coreless Wiring Board Reinforcing Patterns for Warping Control
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Solution Overview
Problem
Conventional wiring boards without a core (coreless boards) suffer from rigidity issues due to thermal expansion coefficient differences between materials, leading to warping, which existing technologies have not adequately addressed.
Innovation Solution
A wiring board design featuring reinforcing patterns in the outer periphery region, formed in the same layers and materials as the wiring layers, with an area ratio matching that of the wiring layers, eliminating gaps and enhancing rigidity to counteract thermal expansion-induced warping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a coreless board structure is used to achieve thin manufacturing, then the thickness of the wiring board is reduced, but the rigidity of the wiring board decreases leading to warping
Solution Approach 1:
The outer periphery region is segmented into multiple layers with reinforcing patterns formed in alternating insulating layers. This segmentation approach allows the reinforcing patterns to be distributed throughout the structure, providing localized rigidity enhancement without increasing overall thickness. The reinforcing patterns are formed in specific layers (first, third, fifth insulating layers) to create a segmented reinforcement strategy that counteracts warping while maintaining thin profile.
Solution Approach 2:
The wiring board employs a composite structure combining different materials with complementary properties: copper wiring layers provide electrical functionality, while reinforcing patterns made of conductive material embedded in insulating layers provide structural rigidity. The alternating arrangement of insulating layers with and without reinforcing patterns creates a composite material system that balances flexibility and rigidity, preventing warping in the thin coreless board structure.
2Ease of manufacture
If thermal treatment is applied during manufacturing, then semiconductor chips are mounted and resin is cured, but thermal expansion coefficient differences cause warping
Solution Approach 1:
The reinforcing patterns are strategically positioned in alternating insulating layers to compensate for thermal expansion stresses. During thermal treatment, different materials expand at different rates, creating internal stresses. The distributed reinforcing patterns act as stress distribution elements, with their alternating arrangement allowing them to counteract the cumulative thermal expansion forces from multiple material layers, thereby preventing warping during chip mounting and resin curing processes.
Solution Approach 2:
The reinforcing patterns are pre-formed in the insulating layers before chip mounting and resin curing. This beforehand cushioning provides structural support that anticipates and counteracts the warping forces that will occur during subsequent thermal treatment. The reinforcing patterns are positioned to provide preemptive resistance against thermal expansion-induced deformation, ensuring stability during the manufacturing process.
3Strength
If the area ratio of reinforcing patterns matches the wiring layer area ratio, then rigidity is enhanced uniformly, but manufacturing precision requirements increase
Solution Approach 1:
The reinforcing patterns are formed using the same photolithography and plating processes as the wiring layers, essentially copying the manufacturing methodology. The area ratio matching is achieved by applying the same pattern formation rules to both wiring layers and reinforcing patterns - using identical design rules, spacing, and dimensional parameters. This copying approach ensures that the area ratios are naturally matched without requiring separate precision control, as both feature types are manufactured through the same process steps with the same tolerances.
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
The solution significantly increases the rigidity of the wiring board, reducing warping both before and after electronic component mounting, and when covered with resin, thereby enhancing the reliability of chip mounting and preventing cracks.
Implementation Method 1
warp is considered to be caused by a thermal expansion coefficient difference between resin used in an interlayer insulating film or a solder resist layer and a wiring layer
Implementation Method 2
The reinforcing patterns are formed in the same layers as the wiring layers, and have substantially the same area ratio as the wiring layers, so that rigidity of the entire wiring board is enhanced, and uneven stress is eliminated
Data Source
AI summary
A wiring board includes a wiring forming region in which a plurality of wiring layers are stacked while sandwiching insulating layers, an outer periphery region which is arranged around the wiring forming region and in which a reinforcing pattern is formed in the same layer as each of the wiring layers. An area ratio of the reinforcing pattern to the outer periphery region and an area ratio of the wiring layer to the wiring forming region are substantially the same in each of the layers, and the reinforcing patterns exist without a gap in the outer periphery region when the wiring board is viewed in planar perspective.