Solder Paste Standoff Particles for Low-Profile PCB Venting

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Solution Overview

Problem

Low-profile components on printed circuit boards face challenges with flux outgassing due to poor venting channels, leading to insufficiently solidified flux residue, mobility of active ingredients, and potential corrosion, which can cause parasitic leakage and electrochemical migration.

Innovation Solution

Incorporating oversized, spherical particles into the solder paste that resist melting and create venting channels between components and the PCB, allowing for proper outgassing of volatiles during the reflow process, with a concentration range of 3% to 8% and sizes optimized for a three-point seating plane.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of moving object

If low-profile components are used to conserve space on PCB, then area of component is reduced, but flux outgassing is blocked leading to corrosion and reliability issues

Engineering Contradiction:

Improvecomponent footprintVSAvoidflux outgassing

Core Design Contradiction:

Area of moving objectVSReliability

Solution Approach 1:

The patent introduces porous or hollow spherical particles into the solder paste formulation. These particles create internal void spaces that serve as channels for flux outgassing during reflow soldering, allowing volatiles to escape while maintaining the low-profile component attachment. This resolves the contradiction by providing outgassing pathways without increasing the component footprint.

Inventive Principle:

Principle #31Porous materials

Solution Approach 2:

The patent uses spherical particles as intermediary elements between the solder paste and the low-profile component. These particles act as a mediator that provides outgassing channels while transferring the mechanical and thermal properties needed for reliable soldering. The particles enable flux volatiles to escape during reflow without compromising the integrity of the low-profile component attachment.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If traditional solder paste is used without standoff particles, then manufacturing process is simple, but solder collapse occurs and venting channels are insufficient

Engineering Contradiction:

Improveprocess simplicityVSAvoidventing channel formation

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent modifies the physical and chemical parameters of the solder paste by incorporating spherical particles with specific size ranges (0.5-5 micrometers), porosity levels (50-90%), and concentration ranges (1-10% by weight). These parameter changes enable the formation of adequate venting channels during reflow while maintaining a straightforward manufacturing process that requires only standard solder paste application techniques.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If standoff particles are added to create venting channels, then flux outgassing is improved, but solder paste formulation complexity increases

Engineering Contradiction:

Improveflux outgassingVSAvoidsolder paste formulation

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent employs inexpensive spherical particles that serve their primary function of providing outgassing channels during the reflow process. These particles are designed to be consumed or transformed during soldering, with their temporary presence enabling flux volatile escape. The use of cost-effective, single-use particles minimizes the impact on overall manufacturing complexity while achieving the reliability improvement.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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

Prevents solder collapse, ensures proper solidification of flux, reduces corrosion risks, and enhances the reliability of low-profile component attachments by allowing effective venting of volatiles, thereby reducing the formation of voids and maintaining the integrity of the solder joint.

Implementation Method 1

applying the solder paste to the PCB in a reflow process

Methodology Applied

Scientific EffectMelting: Melting

Implementation Method 2

the plurality of standoff particles prevent gasketing under the component and allow for outgassing of flux from the solder paste

Methodology Applied

Scientific EffectOutgassing: Evaporation

Data Source

PatentUS11812562B2Creating a standoff for a low-profile component without adding a process step

Publication Date: 2023.11.07 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

Aspects of the invention include receiving a printed circuit board (PCB) having one or more of mounting pads thereon, determining a stencil for applying a solder paste to the one or more mounting pads, the stencil having a smallest aperture for a component requiring a standoff, determining a maximum threshold size for standoff particles based on the smallest aperture, determining a first concentration of the standoff particles based on the smallest aperture, determining a minimum threshold size for standoff particles to create the standoff for the component, determining a second concentration of the standoff particles to create a three-standoff seating plane for the component, introducing the standoff particles to the solder paste, the standoff particles in the solder paste having a concentration between the first concentration and the second concentration, and a size between the maximum threshold size and the minimum threshold size.