What is mechanical decapsulation, and how does it help in failure analysis of chip packages?

Mechanical decapsulation is an alternative method to chemical etching for exposing the die backside in chip packages. It involves physically removing the packaging material to reveal the die, offering a more controlled and precise approach compared to using harsh chemicals. This helps in preserving the integrity of delicate components like copper leads, which are essential for accurate electrical measurements during failure analysis.

What risks does chemical etching pose to copper leads in small, non-exposed die pad packages?

Chemical etching, particularly with 65% Acid Nitric Fuming at 50 degrees Celsius, poses risks to copper leads in small, non-exposed die pad packages. The acid can aggressively corrode the copper, leading to over-etching, erosion, or breakage of the leads. Such damage compromises the ability to perform accurate electrical measurements, which are critical for effective failure analysis.

How do the limitations of chemical etching specifically affect package designs with large die pad areas and small lead areas?

The limitations of chemical etching, such as the risk of over-etching copper leads, especially affect package designs with large die pad areas and small lead areas. In these cases, the acid can quickly corrode the smaller leads while exposing the larger die pad, making chemical etching unsuitable due to the potential for compromising electrical measurements. Mechanical decapsulation is better suited for delicate parts.

What protective measures are typically taken during chemical etching to safeguard copper leads, and why are they sometimes insufficient?

To protect copper leads during chemical etching, they are typically sealed with 3M High Temperature Polyimide Tape before the etching process. However, even with this precaution, the aggressive nature of acids like 65% Acid Nitric Fuming at 50 degrees Celsius can still cause over-etching, particularly in areas with smaller lead dimensions. This is why alternative methods like mechanical decapsulation are considered.

How does mechanical decapsulation ensure more reliable electrical measurements compared to chemical etching, and what are the implications for failure analysis?

Mechanical decapsulation ensures more reliable electrical measurements by mitigating the risk of over-etching and preserving the integrity of copper leads during backside sample preparation. By using physical methods to remove the packaging material, this technique avoids the corrosive effects of chemicals, allowing for more accurate and consistent electrical measurements, which enhances the overall effectiveness of failure analysis. The implications of accurate measurements translates into lower failure rates and continuous improvement.

Mechanical decapsulation of a microchip revealing its internal circuitry.

Unlocking Chip Secrets: A Guide to Backside Decapsulation for Failure Analysis

Kai Mendoza in Tech & Innovation August 2025 • 4 min read.

"Discover how mechanical decapsulation can revolutionize failure analysis in non-exposed die pad packages, ensuring accuracy and efficiency."

In today's fast-paced microelectronics industry, the demand for increasingly complex chips is ever-growing. With this complexity, however, comes a higher susceptibility to failures caused by external electrical stress or manufacturing defects. Identifying the root cause of these failures quickly and accurately is crucial for maintaining product quality and reliability.

One essential technique used in failure analysis is exposing the die backside, often achieved through chemical preparation. While effective, this method has significant drawbacks, especially when dealing with small, non-exposed die pad packages. The risk of over-etching copper leads with harsh chemicals like 65% Acid Nitric Fuming can hinder further electrical measurements, rendering the process ineffective.

This article explores an innovative solution: mechanical decapsulation. This alternative method offers a more controlled and precise approach to backside sample preparation, ensuring the copper leads remain intact and enabling accurate electrical measurements. Learn how this technique can revolutionize your failure analysis process and improve the overall effectiveness of your results.

The Problem with Chemical Etching

Mechanical decapsulation of a microchip revealing its internal circuitry.

Traditional chemical etching has long been a standard practice for exposing the die backside. It's generally known for its speed and ability to deliver a clean surface. However, its application is not without challenges, especially when dealing with delicate packages. Small, non-exposed die pad packages, where the die is fully covered with mold compound, are particularly vulnerable.

The issue arises after the backside copper die pad and leads are exposed. To protect the leads, they are typically sealed with 3M High Temperature Polyimide Tape. Despite this precaution, the etching process using acid nitric (HNO3 65% Fuming) at 50 degrees Celsius for just 5-10 minutes can easily lead to over-etching. This occurs because the highly reactive acid quickly corrodes the copper, especially in areas with smaller lead dimensions.

Copper Lead Damage: The acid can aggressively attack the copper leads, causing them to erode or even break.
Measurement Hindrance: Damaged leads compromise the ability to perform accurate electrical measurements, a critical step in failure analysis.
Limited Application: Chemical etching becomes unsuitable for package designs with large die pad areas and small lead areas due to this over-etching risk.

With the limitations of chemical etching laid bare, it's clear that an alternative is needed for certain types of packages. Mechanical decapsulation emerges as a viable solution, offering greater control and precision in exposing the die backside without compromising the integrity of the copper leads. This method not only preserves the leads but also ensures the reliability of subsequent electrical measurements, thereby enhancing the accuracy of failure analysis.

Embracing the Future of Failure Analysis

In conclusion, mechanical decapsulation presents a compelling alternative to chemical etching for backside sample preparation, particularly in non-exposed die pad package designs. By mitigating the risk of over-etching and preserving the integrity of copper leads, this technique ensures more reliable electrical measurements and enhances the overall effectiveness of failure analysis. As the microelectronics industry continues to advance, embracing innovative methods like mechanical decapsulation will be crucial for maintaining product quality, reducing failure rates, and driving continuous improvement.