Solder Bump Reflow Using Segmented Top-Down Heating

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Solution Overview

Problem

In semiconductor device production, the conventional reflow processing of solder bumps, where heating is applied from below, leads to uneven melting and increased likelihood of short circuits due to reduced spacing between bumps, as the superior and inferior portions melt at different times, causing thermal vibrations and potential contact between neighboring bumps.

Innovation Solution

A dual heating system is employed, where the superior portion of the bump is first heated to initiate melting, followed by heating the entire bump, ensuring homogeneous melting and preventing short circuits by maintaining a stable, spherical configuration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If heating is applied from below to melt solder bumps, then the bumps are melted and reflowed, but the superior and inferior portions melt at different times causing thermal vibrations and potential contact between neighboring bumps

Engineering Contradiction:

Improvebump melting temperatureVSAvoidshort circuit prevention

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The heating process is segmented into two distinct phases: first heating only the superior portion of the bump to initiate melting, then heating the inferior portion to complete the melting process. This segmentation ensures that the bump melts uniformly from top to bottom without thermal vibrations that could cause neighboring bumps to contact and create short circuits.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The superior portion of the bump is heated and melting is initiated before the inferior portion is heated. This preliminary action on the superior portion creates a controlled melting sequence that prevents sudden thermal expansion and vibration, thereby preventing contact between neighboring bumps.

Inventive Principle:

Principle #10Preliminary action

2Productivity

If the distance between solder bumps is reduced for miniaturization, then high integration is achieved, but the likelihood of bump contact and short circuit increases

Engineering Contradiction:

Improveintegration densityVSAvoidshort circuit prevention

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

By segmenting the heating process into two stages (superior portion first, then inferior portion), the invention enables safe reduction of bump spacing. The controlled melting sequence prevents thermal vibrations that would otherwise cause contact between closely spaced bumps, allowing miniaturization without sacrificing reliability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The heating parameters are changed from a single-source bottom-up approach to a two-stage top-then-bottom approach. This parameter change in the heating sequence allows for reduced bump pitch while maintaining reliability, as the controlled melting prevents the thermal vibrations that lead to short circuits.

Inventive Principle:

Principle #35Parameter changes

3Temperature

If the bump is heated from below, then the entire bump is heated, but the melting timing difference between superior and inferior portions causes thermal vibration

Engineering Contradiction:

Improvebump temperature uniformityVSAvoidbump shape stability

Core Design Contradiction:

TemperatureVSStability of the object's composition

Solution Approach 1:

Instead of heating from below as conventionally done, the invention inverts the heating sequence by first heating the superior portion and then the inferior portion. This inversion of the heating direction eliminates thermal vibrations and maintains bump shape stability during the melting process.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The superior portion is heated and melting is preliminarily initiated before the inferior portion is heated. This preliminary heating action creates a controlled melting front that moves smoothly from top to bottom, preventing thermal vibrations and maintaining shape stability.

Inventive Principle:

Principle #10Preliminary action

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 approach prevents short circuits and ensures reliable reflow of solder bumps, even at reduced spacings, meeting the demands of miniaturization and high integration in semiconductor devices and electronic components.

Implementation Method 1

first melting by heating only a superior portion of a bump formed on an electrode on one principle surface of a semiconductor substrate

Methodology Applied

Scientific EffectHeating: Heating

Implementation Method 2

second melting the entire bump by also heating an inferior portion of the bump

Methodology Applied

Scientific EffectHeating: Heating

Implementation Method 3

first melting by heating only a superior portion of a bump

Methodology Applied

Scientific EffectMelting: Melting

Data Source

PatentUS8302843B2Process for producing semiconductor device and apparatus therefor

Publication Date: 2012.11.06 SOCIONEXT INC

AI summary

A process for producing a semiconductor device, includes: first melting by heating only a superior portion of a bump formed on an electrode on one principle surface of a semiconductor substrate; and second melting the entire bump by also heating an inferior portion of the bump.