PCB Stack Overflow Grooves for Glue Control
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Solution Overview
Problem
The transient liquid phase sintering method for connecting modules to main boards faces challenges such as glue overflow during press-bonding, leading to residue issues, alignment accuracy problems, and increased costs due to the need for a glue blocking material, which is difficult to inspect and reuse.
Innovation Solution
A printed circuit board stack structure with overflow grooves and retaining walls on the first surface board prevents glue overflow by accommodating the filling glue layer within these grooves, eliminating the need for a glue blocking material and improving electrical reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a glue blocking material is used to prevent glue overflow during press-bonding, then glue overflow is prevented, but the main board cannot be processed and has to be scrapped due to residues when the glue blocking material is peeled off
Solution Approach 1:
The harmful glue blocking material is completely removed from the system. Instead of using a separate blocking material that causes residues and scrap issues, the patent extracts this function entirely by using the filling glue layer itself as the blocking structure through direct application without requiring peeling or removal.
Solution Approach 2:
The filling glue layer serves dual purposes: it fills the bonding area and simultaneously acts as the blocking material for non-bonding areas. The glue layer self-containedly performs both bonding and blocking functions, eliminating the need for separate glue blocking materials that cause residues and processing issues.
2Object-generated harmful factors
If a glue blocking material is used to prevent glue overflow, then glue overflow is controlled, but the cost increases and the glue blocking material cannot be used repeatedly
Solution Approach 1:
The patent replaces expensive, non-reusable glue blocking materials with a cheap, disposable filling glue layer that is applied directly and serves its purpose in a single use. The filling glue layer is inexpensive compared to specialized blocking materials and is discarded with the product rather than requiring recovery or reuse.
Solution Approach 2:
The filling glue layer performs multiple functions: it bonds the module to the main board, fills the bonding area, and blocks the non-bonding area. This multi-functionality eliminates the need for separate blocking materials, reducing overall manufacturing cost and simplifying the process.
3Object-generated harmful factors
If a glue blocking material is used to prevent glue overflow, then glue overflow is prevented, but the alignment accuracy between the module and the main board is reduced
Solution Approach 1:
The filling glue layer is applied in advance to define the bonding and non-bonding areas before the module is positioned. This preliminary action establishes precise boundaries that guide alignment, ensuring accurate positioning of the module relative to the main board before bonding occurs.
Solution Approach 2:
The filling glue layer creates different local properties: a cured bonding area with specific characteristics for strong adhesion and an uncured non-bonding area that acts as a blocking material. This local differentiation provides clear visual and tactile cues for precise alignment during the bonding process.
4Stability of the object's composition
If the glass transition temperature of the glue blocking material is matched to the filling glue and copper paste, then the glue blocking material can function properly, but the selection of filling glue and copper paste is restricted
Solution Approach 1:
The temperature matching constraint is extracted from the system by removing the glue blocking material entirely. Without this separate material, there is no temperature matching requirement, allowing free selection of filling glue and copper paste based on their own performance characteristics without being constrained by compatibility with a blocking material's glass transition temperature.
Solution Approach 2:
The filling glue layer performs both bonding and blocking functions without requiring a separate glue blocking material. This self-service approach eliminates the temperature matching constraint entirely, as the filling glue's own thermal properties are sufficient for both its bonding function and its role in defining non-bonding areas, providing complete material selection flexibility.
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 solution prevents glue overflow to non-bonding areas, enhances electrical reliability, reduces costs by eliminating residue issues, and improves yield by eliminating the need for a glue blocking material.
Implementation Method 1
transient liquid phase sintering (TLPS) refers to sintering carried out by the transfer of low-melting-point metal to the liquid phase caused by the heating of the low-melting-point metal at the particle interface and the reaction diffusion of high-melting-point metal to the formed liquid phase
Data Source
AI summary
A printed circuit board stack structure includes a first printed circuit board, a second printed circuit board, and a filling glue layer. The first printed circuit board has at least one overflow groove, and includes first pads and a retaining wall surrounding the first pads. The second printed circuit board is disposed on the first printed circuit board, and includes second pads and conductive pillars located on some of the second pads. The conductive pillars are respectively connected to some of the first pads to electrically connect the second printed circuit board to the first printed circuit board. The filling glue layer fills between the first and the second printed circuit boards, and covers the first pads, the second pads, and the conductive pillars. The retaining wall blocks the filling glue layer so that a portion of the filling glue layer is accommodated in the overflow groove.