Multilayer Substrate Via Hole Tapering for Paste Exudation Control
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Solution Overview
Problem
Existing multilayer substrates face limitations in reducing the pitch of via conductors due to dimensional accuracy issues caused by conductive paste exudation during the manufacturing process, which inhibits the decrease in pitch and affects the mounting of components with narrow terminal arrangements.
Innovation Solution
The multilayer substrate incorporates via holes with a specific diameter enlargement degree, where the enlargement toward the upper end position is greater than toward the intermediate position, allowing for lower filling pressure and reduced paste exudation, resulting in improved dimensional accuracy of via conductors. This configuration enables the use of via conductors as mounting electrodes for components with narrow pitch terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If via holes are filled with conductive paste using conventional methods, then via conductors are formed, but conductive paste exudes from the openings causing dimensional accuracy variation
Solution Approach 1:
The patent changes the geometric parameters of the via hole by forming a tapered shape with a smaller opening diameter at the paste filling side compared to the other side. This parameter change allows the conductive paste to be contained more effectively during filling, preventing exudation and improving dimensional accuracy of the via conductors.
2Productivity
If the pitch of via conductors is decreased to mount components with narrow terminal arrangements, then component mounting capability is improved, but dimensional accuracy variation increases due to paste exudation
Solution Approach 1:
By changing the via hole shape to a tapered configuration with different opening diameters at each end, the patent enables smaller pitch between via conductors while maintaining dimensional accuracy. The tapered shape prevents paste exudation even at reduced pitches, allowing successful mounting of components with narrow terminal arrangements.
3Reliability
If mounting electrodes are provided with areas larger than via conductor end surfaces, then connection reliability is improved, but the pitch of mounting electrodes cannot be decreased further
Solution Approach 1:
The patent changes the via hole geometry to create a tapered shape that allows the via conductor end surface to serve directly as the mounting electrode. This parameter change eliminates the need for separate mounting electrodes with larger areas, enabling direct component mounting at the via conductor ends with reduced pitch.
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 improved dimensional accuracy of via conductors allows for a narrower pitch between them, facilitating the mounting of components with narrow pitch terminals and increasing wiring density, thereby reducing the size of the multilayer substrate while ensuring strong connections.
Implementation Method 1
predetermined positions of the insulating layers formed by ceramic green sheets or the like are irradiated with laser light from one main surface side of the insulating layers so as to form via holes passing through the insulating layers
Data Source
AI summary
A multilayer substrate including a multilayer body formed by laminating a plurality of insulating layers including via holes in the insulating layer as an uppermost layer of the multilayer body so as to pass through the insulating layer, and via conductors formed by filling the via holes with a conductive paste. The via holes are formed through lower end positions, upper end positions, and intermediate positions between the lower end positions and the upper end positions such that a diameter enlargement degree toward the upper end positions from the intermediate positions is larger than a diameter enlargement degree toward the intermediate positions from the lower end positions. By forming the via holes as described above, when the via holes are filled with the conductive paste from openings at the small diameter side of the via holes, exudation of the conductive paste from openings at the large diameter side is prevented.