Semiconductor Lead Frame Solder Intrusion Barrier

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Solution Overview

Problem

The reliability of semiconductor devices with surface mount packages is compromised due to solder intrusion into gaps between the resin package and the metal frame, which affects their bonding strength and solder wettability, making it difficult to inspect and maintain them effectively.

Innovation Solution

The semiconductor device incorporates a third lead frame that is continuously exposed from the back surface to the side surface of the resin package, forming a boundary that prevents solder penetration and allows for visual inspection of solder wettability, while also being designed to match prescribed pad shapes to prevent positional misalignment during reflow processes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If solder paste is applied and reflow soldering is performed to mount the semiconductor device, then the semiconductor device is properly fixed to the printed circuit board and solder wettability can be inspected, but solder penetrates into the gap between the resin package and the frame, reducing reliability

Engineering Contradiction:

Improvebonding strengthVSAvoidsolder intrusion

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A third frame is introduced as an intermediary element between the first and second frames. This third frame acts as a barrier that prevents solder from penetrating into the gap between the resin package and the first/second frames, while still allowing the solder fillet to form properly on the end faces of the first and second frames for inspection purposes.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The frame structure is segmented into multiple independent frames (first frame, second frame, and third frame) rather than using a single continuous frame. This segmentation allows the third frame to be positioned specifically to block solder intrusion paths while leaving the end faces of the first and second frames exposed for solder wettability inspection.

Inventive Principle:

Principle #1Segmentation

2Difficulty of detecting and measuring

If the end face of the frame is exposed at the side surface of the package for solder wettability inspection, then the presence or absence of solder fillet can be observed, but the solder climbs up the end surface and penetrates into the gap between the resin package and the frame

Engineering Contradiction:

Improvesolder wettability inspectionVSAvoiddevice reliability

Core Design Contradiction:

Difficulty of detecting and measuringVSReliability

Solution Approach 1:

The third frame serves as a protective intermediary that blocks the harmful solder penetration into the gap between the resin package and the first/second frames, while allowing the first and second frames to maintain their exposed end faces for inspection purposes.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

Different portions of the frame structure have different functions: the first and second frames have exposed end faces for solder wettability inspection, while the third frame has a configuration specifically designed to prevent solder intrusion into the gap between the resin package and the other frames.

Inventive Principle:

Principle #3Local quality

3Reliability

If a third frame is added to prevent solder intrusion, then solder penetration is blocked and reliability is enhanced, but the device structure becomes more complex

Engineering Contradiction:

Improvebonding yieldVSAvoidframe structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The third frame performs multiple functions simultaneously: it acts as a barrier to prevent solder intrusion into the gap between the resin package and the first/second frames, maintains structural integrity of the package, and does not interfere with the solder wettability inspection of the first and second frames. This multi-functionality justifies the additional structural element.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 configuration enhances the reliability and bonding yield of semiconductor devices by blocking solder intrusion and enabling visual inspection of solder wettability, reducing manufacturing costs and improving the reliability of printed circuit boards.

Implementation Method 1

the solder wettability of the frame can be examined by observing the presence or absence of the fillet, which is the climbing-up solder formed on an end face of the frame

Methodology Applied

Scientific EffectCapillary action: Capillary Action

Implementation Method 2

the third frame is continuously exposed from the back surface to the side surface in contact with the back surface, blocking the solder penetration

Methodology Applied

Scientific EffectPhysical barrier blocking: Physical Containment

Data Source

PatentUS8536686B2Semiconductor device

Publication Date: 2013.09.17 NICHIA CORP

AI summary

According to an embodiment, a semiconductor device includes a first frame, a semiconductor element fixed to the first frame, a second frame, a third frame and a resin package. The second frame faces the first frame and is away from the first frame, the second frame being electrically connected to the semiconductor element via a metal wire. The resin package covers the semiconductor element, the first frame, and the second frame. The first frame and the second frame are exposed in one major surface of the resin package. The third frame juxtaposed to one of the first frame and the second frame, the third frame being continuously exposed from the major surface of the resin package to a side surface in contact with the major surface.