Multilayer PCB Assembly Using Diffusion Soldering for Buried Components
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Solution Overview
Problem
Existing methods for connecting buried components in printed circuit boards face issues with solder reflow, leading to short-circuits and delamination, especially in aeronautical applications where standard components are not compatible with high-temperature soldering.
Innovation Solution
A method using a solder paste containing copper and tin for diffusion soldering, allowing assembly of buried components without reflow, combined with a separate solder bead for outer components, ensuring distinct melting temperatures to prevent short-circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the same soldering method (SAC305 alloy) is used to connect both buried and outer components, then standard components and assembly techniques can be used, but solder reflow occurs in inner layers causing short-circuits
Solution Approach 1:
The patent divides the soldering process into two distinct stages: first connecting buried components to inner conductive layers using a high-melting-point solder paste (containing copper balls and tin), then connecting outer components to outer conductive layers using conventional SAC305 solder bead. This segmentation prevents reflow of inner layer solder during outer component assembly, eliminating short-circuit risks while maintaining compatibility with standard components.
Solution Approach 2:
The patent applies different soldering materials to different regions of the circuit board: high-melting-point solder paste (with copper balls) is used specifically for buried components in inner layers, while conventional SAC305 solder bead is used for outer components. This local differentiation ensures that each region receives the appropriate soldering material with suitable melting characteristics, preventing unwanted reflow in inner layers.
2Reliability
If high-temperature soldering is used to connect buried components, then solder reflow is prevented, but standard components become incompatible
Solution Approach 1:
The patent segments the assembly process into two phases: first, connecting buried components using high-melting-point solder paste at elevated temperatures (preventing reflow); second, connecting outer components using conventional SAC305 solder bead at standard temperatures. This temporal and material segmentation allows high-temperature processing for buried components without affecting the compatibility of standard outer components.
Solution Approach 2:
The patent performs the buried component assembly and solder paste application before outer component installation. By completing the inner layer connections first with high-melting-point solder paste, the board is prepared in advance, allowing subsequent outer component assembly with conventional soldering materials without risking reflow of inner layer solder.
3Ease of manufacture
If conventional soft soldering is used for buried components, then standard assembly techniques are used, but solder reflow occurs during subsequent outer component assembly
Solution Approach 1:
The patent segments the soldering process into two distinct operations: first using diffusion soldering with copper-terminated solder paste for buried components, then using conventional soft soldering with SAC305 bead for outer components. This segmentation enables simple, standard assembly techniques for outer components while preventing solder reflow in inner layers through the use of high-melting-point paste in the first stage.
Solution Approach 2:
The patent introduces a special high-melting-point solder paste (containing copper balls and tin) as an intermediary material for connecting buried components. This intermediary solder paste serves as a stable base that does not reflo during subsequent conventional soldering operations, thereby preventing short-circuits while maintaining ease of manufacture through a two-stage process.
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 method prevents solder reflow in inner layers, enabling reliable connection of buried components without short-circuits, compatible with standard components and boards, and facilitating cleaning and adhesion during multilayer board manufacturing.
Implementation Method 1
soldering by diffusion said electronic component
Data Source
AI summary
A method for mounting an electronic component to a conductive layer of a printed circuit board, the method including 1) depositing a solder paste on the conductive layer, the solder paste including tin, copper balls and a solder flux; 2) positioning the electronic component on the solder paste; then 3) diffusion-soldering the electronic component. Another aspect relates to a method for producing a multilayer printed circuit board, the method including a) mounting at least a first electronic component on an inner conductive layer of a printed circuit board; b) depositing a dielectric layer on the first electronic component and the inner conductive layer; and c) mounting at least a second electronic component on an outer conductive layer of the printed circuit board.