Lead Frame Isolation Dam for Adhesive Bleed Control
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Solution Overview
Problem
Adhesive resins in semiconductor packages tend to bleed or spread into the space between lead frames, causing bridging, arcing, and poor isolation performance due to their viscous nature.
Innovation Solution
A solder resist (S/R) dam is used between the integrated circuit die and the lead frame, which is smaller than the die in width and length dimensions, preventing adhesive resin from spreading into the space between the lead frames by overhanging on each side and being attached to the die or lead frame, thereby controlling the adhesive's location.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive resin is applied to attach the semiconductor die to the lead frame, then the die is securely attached, but the adhesive resin spreads into the space between lead frames causing bridging and arcing
Solution Approach 1:
A dam structure is introduced as an intermediary element between the adhesive resin and the space between lead frames. The dam acts as a physical barrier that prevents the adhesive from spreading into critical areas while allowing the adhesive to perform its attachment function. This mediator structure resolves the contradiction by enabling secure attachment without compromising isolation performance.
Solution Approach 2:
The dam structure segments the adhesive application area, creating distinct zones: an area where adhesive is allowed to spread for secure attachment, and a protected area between lead frames where adhesive spread is prevented. This segmentation allows the system to achieve both strong attachment and reliable isolation simultaneously.
2Strength
If adhesive resin is applied to attach the semiconductor die to the lead frame, then the die is securely attached, but the adhesive resin encroaches upon the HV-LV split DAP spacing
Solution Approach 1:
The dam serves as an intermediary barrier that protects the HV-LV split DAP spacing from adhesive encroachment. It allows the adhesive to be applied freely for secure attachment while preventing the adhesive from invading the precision-critical clearance spacing, thus maintaining manufacturing precision.
Solution Approach 2:
The dam structure is placed in position before the adhesive is applied. This preliminary action establishes the boundaries of adhesive spread in advance, ensuring that when the adhesive is applied, it cannot encroach upon the HV-LV split DAP spacing, thereby guaranteeing the required clearance precision.
3Reliability
If a dam structure is added to prevent adhesive spread, then isolation performance is improved, but device complexity increases
Solution Approach 1:
The dam is implemented as a thin film or flexible barrier structure rather than a bulky rigid component. This approach provides effective isolation performance while minimizing the increase in device complexity and overall package size. The thin film nature of the dam allows it to be integrated into the existing package structure with minimal additional complexity.
Data Source
AI summary
An apparatus includes a lead frame, a dam and adhesive on portions of the lead frame, and an integrated circuit die having a portion on the dam and another portion on the adhesive. The lead frame can include two portions, or two lead frames. The dam can bridge a space between the two lead frames. The dam can be smaller than the integrated circuit die in at least a width dimension of the dam relative to a width dimension of the integrated circuit die, providing that the integrated circuit die overhangs the dam on each side of the width dimension of the dam. Adhesive is located between the integrated circuit die and each lead frame, adjacent to and on each side of the dam. The dam prevents adhesive from spreading into the space between the lead frames.