Bus Bar Terminal Segmentation for PCB Connection Reliability

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Solution Overview

Problem

The connection between bus bars and printed boards often fails due to thermal expansion differences, leading to terminals dislodging during the reflow process, and existing solutions either require costly jigs or damage the printed board when attempting to secure the bus bar.

Innovation Solution

The bus bar terminals are branched and bent to securely engage with the printed board's conductor, eliminating the need for a fixing jig and preventing floating due to thermal expansion differences, while allowing for stable bonding even under inclination or external loads.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a bus bar is secured to a printed board by pressing terminals into through-holes, then connection reliability is improved, but manufacturing precision deteriorates due to small tolerances between terminals and through-holes

Engineering Contradiction:

Improveconnection reliabilityVSAvoidtolerance between terminal and through-hole

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The terminal is divided into multiple segments: a press-fit portion that inserts into the through-hole and multiple bent portions that engage with conductors at different locations. This segmentation allows each part to fulfill its function independently, accommodating tolerance variations while maintaining connection reliability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The terminal extends from the through-hole in the thickness direction of the printed board and then bends laterally to engage with conductors. This dimensional transition from vertical insertion to lateral engagement provides additional degrees of freedom for accommodating misalignment while ensuring secure connection.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Reliability

If a jig is used to hold the bus bar on the printed board during reflow, then connection reliability is improved, but device complexity and cost increase

Engineering Contradiction:

Improveconnection reliabilityVSAvoidjig requirement

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The terminal structure is designed to self-secure the bus bar to the printed board through its bent portions engaging with conductors. This self-fixing mechanism eliminates the need for external jigs or fixtures during the reflow process, simplifying the manufacturing system while maintaining connection reliability.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The terminal is pre-formed with bent portions before assembly. When the bus bar is positioned on the printed board, these pre-formed bent portions automatically engage with the conductors, providing preliminary securing action before the reflow process begins, thus eliminating the need for additional holding devices.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If the terminal is bent to prevent floating, then connection reliability is improved, but the printed board may be damaged

Engineering Contradiction:

Improveconnection reliabilityVSAvoidprinted board damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The terminal exhibits different geometries at different locations: a straight press-fit portion for insertion into the through-hole and bent portions for engaging conductors. This local differentiation allows the terminal to prevent floating and secure the bus bar without requiring excessive force that could damage the printed board.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The terminal includes bent portions with curved geometries that engage with the conductors. These curved portions provide mechanical interlocking while distributing stress evenly, preventing floating without concentrating force at single points that could damage the printed board.

Inventive Principle:

Principle #14Spheroidality (Curvature)

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 reliably prevents bus bar disconnection from the printed board, reduces the need for costly jigs, and ensures stable bonding under varying conditions, thereby lowering production costs and improving connection reliability.

Implementation Method 1

a terminal extending from the bus bar is inserted into a through-hole in the printed board body and bonded, e.g. by soldering, to a printed conductor provided on the other side of the printed board body

Methodology Applied

Scientific EffectSoldering: Soldering

Implementation Method 2

the terminal can dislodge and float upward from a through-hole in the printed board due to a difference in coefficient of thermal expansion between the printed board and the bus bar under the high temperature atmosphere

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 3

the bonders are melted to interconnect the bus bar and the printed board

Methodology Applied

Scientific EffectMelting: Melting

Data Source

PatentUS8701971B2Printed board and bus bar assembly

Publication Date: 2014.04.22 SUMITOMO WIRING SYSTEMS LTD

AI summary

A printed board includes a printed board body having a first side, a second side opposing the first side, and a through-hole; a printed conductor disposed on the first side of the printed board body; and a bus bar disposed on the second side of the printed board body, the bus bar including a terminal that extends through the through-hole. The terminal includes a plurality of branched terminal portions at a position corresponding to an interior of the through-hole, and at least one of the branched terminal portions is bent and attached to the printed conductor.