3D Press-Fit Electrical Contact for Stress-Relieved PCB Joining

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Solution Overview

Problem

Existing semiconductor device packages face challenges in achieving reliable solderless electrical connections and efficient stress relief during the mating process of press-fit pins with PCBs, often leading to issues like coefficient of thermal expansion mismatch and inadequate adhesion.

Innovation Solution

The development of electrical contacts comprising two components with prongs that flex radially to form a one-body pin, featuring stress relief slots and trenches, which are coupled together to provide enhanced adhesion and prevent axial movement, allowing for optimal cold welding and reduced thermal expansion mismatch.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If press-fit pins are used to establish solderless electrical connections, then ease of manufacture is improved, but reliability of electrical connection deteriorates due to coefficient of thermal expansion mismatch and inadequate adhesion

Engineering Contradiction:

Improveease of manufactureVSAvoidreliability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The pin is divided into multiple segments including a head portion, a body portion, and an array of prongs. The prongs can independently flex radially to accommodate thermal expansion differences while maintaining electrical contact, thus resolving the contradiction between ease of manufacture and connection reliability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The prongs are designed to be flexible and capable of radial movement. This dynamic capability allows the pin to adapt to thermal expansion mismatches between different materials (PCB, carrier, pin) while maintaining reliable electrical connection, solving the reliability issue without compromising manufacturing simplicity

Inventive Principle:

Principle #15Dynamics

2Reliability

If prongs are designed to flex radially to accommodate thermal expansion, then reliability is improved, but device complexity increases

Engineering Contradiction:

ImprovereliabilityVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The pin is segmented into a head portion, body portion, and multiple prongs. This segmentation allows the prongs to flex independently for thermal accommodation while keeping the overall structure relatively simple and manufacturable

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The prongs are designed as flexible elements that can bend radially. This flexibility provides thermal expansion compensation without requiring complex active control mechanisms, thus improving reliability while minimizing added complexity

Inventive Principle:

Principle #30Flexible shells and thin films

3Reliability

If stress relief slots and trenches are added to the pin structure, then reliability is improved through stress relief, but manufacturing precision requirements increase

Engineering Contradiction:

ImprovereliabilityVSAvoidmanufacturing precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The pin includes stress relief slots and trenches that divide the structure into manageable sections. These features help distribute and relieve stress while maintaining reasonable manufacturing tolerances through the segmented design

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The stress relief features modify the physical parameters of the pin structure by introducing controlled geometric variations (slots and trenches). These parameter changes enable stress management while keeping manufacturing precision requirements within achievable limits

Inventive Principle:

Principle #35Parameter changes

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 solution ensures stable, solderless connections with improved adhesion and stress relief, reducing the footprint while maintaining reliable electrical conductivity and thermal stability across varying temperatures.

Implementation Method 1

The free end of the prongs may be configured to flex, e.g., radially away and/or towards the lengthwise axis to change the width of the base slot

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

coefficient of thermal expansion mismatch

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 3

The first set of prongs and the second set of prongs may engage one another to couple the first and second components together

Methodology Applied

Scientific EffectMechanical interlocking: Mechanical Fastener

Implementation Method 4

The first component may be coupled to the conductive layer by a solder

Methodology Applied

Scientific EffectSoldering: Soldering

Implementation Method 5

The second end may include an angled tip to facilitate insertion of the first component into the second component

Methodology Applied

Scientific EffectGeometric guidance: Geometry

Data Source

PatentEP3968466B1Electrical contact for semiconductor package

Publication Date: 2025.06.25 IXYS SEMICON

Figure 1A~1B
Figure 1C~2
Figure 3A~4C

AI summary

Provided herein are semiconductor packages with improved electrical contacts (e.g. pins). An assembly may include a substrate and an electrical contact coupled to the substrate, the electrical contact consisting of a first component defined by a complex 3D designed receiving pin. The electrical contact may further include a second component defined by another complex 3D designed penetrating pin, wherein the first component engages the second component to deform mechanically and to weld when the first component and the second component are coupled together.