Die Pad Support Pillars to Prevent Resin Flashing in Pre-Molding

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

In the production of semiconductor devices with half-etched die pads, the clamping process is ineffective, leading to resin flashing and smearing on the die pad surface, which cannot be effectively removed, resulting in defective products.

Innovation Solution

The introduction of sacrificial pillars on the back side of the die pad, which provide support during pre-molding, ensuring proper clamping and allowing for the removal of the pillars post-molding to create wettable flanks for soldering, while enabling strong adhesion between the pre-mold resin and encapsulation material.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If leadframe clamping during pre-molding is applied to create half-etched die pad, then the die pad structure is formed, but the clamping is not completely effective causing the die pad to become floating and resin flashes occur

Engineering Contradiction:

Improvedie pad clamping precisionVSAvoidproduct defect rate

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The die pad is segmented into multiple sections with recesses, allowing the mold to clamp each segment separately. This prevents the die pad from floating during injection while maintaining precise positioning, thereby eliminating resin flashes and improving both manufacturing precision and product reliability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The mold applies preliminary clamping force to the die pad segments before resin injection begins. This preliminary action secures the die pad in position, preventing floating and resin flashing during the subsequent injection process

Inventive Principle:

Principle #10Preliminary action

2Shape

If the die pad is left unsupported at the back surface during molding, then the half-etched structure is maintained, but resin smearing and leaking occur on the front surface

Engineering Contradiction:

Improvedie pad half-etched structureVSAvoidsurface finish quality

Core Design Contradiction:

ShapeVSManufacturing precision

Solution Approach 1:

The mold design implements local quality by providing support only at specific locations (die pad segments with recesses) rather than uniform support across the entire die pad. This localized support prevents resin smearing at the front surface while preserving the half-etched structure, thereby improving surface finish quality without compromising the required die pad geometry

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The recesses in the die pad act as intermediaries that allow the mold to indirectly support the die pad structure. The resin can flow into these recesses and provide internal support, preventing smearing on the front surface while maintaining the half-etched configuration

Inventive Principle:

Principle #24Intermediary (Mediator)

3Manufacturing precision

If sacrificial pillars are added to support the die pad during pre-molding, then proper clamping is achieved, but additional manufacturing steps are required

Engineering Contradiction:

Improveclamping effectivenessVSAvoidmanufacturing process complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The sacrificial pillars are merged with the die pad structure itself, forming an integrated component. The pillars are created during the same pre-molding process as the die pad, eliminating the need for separate manufacturing steps. After molding, the pillars are removed along with the formation of wettable flanks in a combined post-processing operation, thereby maintaining manufacturing precision while reducing process complexity

Inventive Principle:

Principle #5Merging (Combining)

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 method ensures a clean die pad surface free from resin flashing and provides robust anchoring of the encapsulation, maintaining the integrity of the leadframe and enhancing the manufacturing yield by preventing resin smearing and distortion.

Implementation Method 1

Strong coupling (adhesion) between the pre-mold resin and the encapsulation can thus be achieved even in the presence of different types and/or amounts of fillers in the pre-mold resin and in the encapsulation

Methodology Applied

Scientific EffectAdhesion: Adhesive

Data Source

PatentUS12456629B2Method of producing substrates for semiconductor device packages comprising anchoring encapsulation to die pad

Publication Date: 2025.10.28 STMICROELECTRONICS SRL

AI summary

A pre-molded leadframe includes a laminar structure having empty spaces therein and a first thickness with a die pad having opposed first and second die pad surfaces. Insulating pre-mold material is molded onto the laminar structure. The pre-mold material penetrates the empty spaces and provides a laminar pre-molded substrate having the first thickness with the first die pad surface left exposed. The die pad has a second thickness that is less than the first thickness. One or more pillar formations are provided protruding from the second die pad surface to a height equal to a difference between the first and second thicknesses. With the laminar structure clamped between surfaces of a mold, the first die pad surface and pillar formations abut against the mold surfaces. The die pad is thus effectively clamped between the clamping surfaces countering undesired flashing of the pre-mold material over the first die pad surface.