BGA Carrier Polymer Collars to Block Solder Diffusion

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Solution Overview

Problem

Ball Grid Array (BGA) designs face challenges such as damage to soft solder spheres, surface oxidation, and intermetallic formation when used directly in sockets, leading to increased contact resistance and degraded reworkability.

Innovation Solution

The implementation of polymer collars as mechanical diffusion barriers on electrically conductive balls, formed by spin-coating a polymer material on the substrate, prevents solid-state solder diffusion and enhances mechanical stability and electrical conductivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If BGA packages are used directly in sockets, then smaller form factor and improved electrical performance are achieved, but damage to solder spheres, surface oxidation, and intermetallic formation occur

Engineering Contradiction:

Improveelectrical performanceVSAvoidsolder sphere damage and oxidation

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A polymer layer is introduced as an intermediary barrier between the solder spheres and the socket environment. This polymer layer prevents direct contact between the solder and harmful external factors (oxidation, mechanical damage), while still allowing the electrical function to operate. The polymer acts as a protective mediator that resolves the contradiction between achieving good electrical performance and preventing solder degradation.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

A thin polymer film is applied over the solder spheres to provide protection. This flexible thin film approach allows the solder to maintain its electrical functionality while being protected from mechanical damage and oxidation. The thin film structure provides the necessary protection without significantly increasing the form factor or compromising the electrical performance.

Inventive Principle:

Principle #30Flexible shells and thin films

2Strength

If polymer layers are added to protect solder spheres, then solder diffusion is inhibited and mechanical stability is enhanced, but device complexity increases

Engineering Contradiction:

Improvejoint shear strengthVSAvoidstructure complexity

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The structure combines different materials (solder spheres, polymer layer, substrate) to create a composite system with enhanced properties. The polymer-solder composite provides both the electrical conductivity of the solder and the protective, diffusion-resistant properties of the polymer, achieving improved joint strength without proportionally increasing complexity.

Inventive Principle:

Principle #40Composite materials

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 polymer collars effectively inhibit solder wicking, maintaining the integrity of the noble metal contact interface and improving joint shear strength by three times, while maintaining electrical conductivity and mechanical stability during thermal aging.

Implementation Method 1

polymer layers as barriers to solid state solder diffusion

Methodology Applied

Scientific EffectDiffusion barrier: Diffusion Barrier

Implementation Method 2

formed by spin-coating a polymer material on the substrate

Methodology Applied

Scientific EffectSpin coating: Spin Coating

Data Source

PatentUS12207398B2Electronic device carrier structures including polymer layers as barriers to solid state solder diffusion and methods of forming the same

Publication Date: 2025.01.21 INTEL CORP

AI summary

An electronic device carrier structure can include a substrate including a plurality of electrical contacts spaced apart on the substrate, a plurality of electrically conductive balls, each of the electrically conductive balls being on a respective one of the plurality of electrical contacts, solder attaching each of the electrically conductive balls to respective ones of the electrical contacts to form an attachment boundary where the solder ends on a surface of each of the plurality of electrically conductive balls, and a polymer layer extending on the substrate onto the plurality of electrically conductive balls to form a surface of the polymer layer at a contact point on the plurality of electrically conductive balls that is above the attachment boundary and below an apex of each of the plurality of electrically conductive balls.