SEMI 3D24 - Guide for Peel Testing of Redistribution Layers and Other Traces Used Within Advanced Packages and Structures -

Abstract

1  Purpose
1.1  Advanced packages such as wafer level packages (WLPs), panel level packages (PLPs), and three-dimensional integrated packages are driving fine traces pattern development for substrates, redistribution layers (RDLs), and interposers. These fine traces are often exposed to the manufacturing process environment, which can result in the degradation of adhesion between the traces and other materials, such as encapsulant, die, and other dielectrics. However, it is difficult to characterize adhesion strength at these relevantly small scales. In addition, they may be further affected by flaws and features absent within the patterns.
1.2  An iNEMI®  project was initiated to evaluate applicable measurement methodologies for conductive trace adhesion and to characterize mechanical performance. Adhesion tests can be classified by whether they measure the initiation or propagation of debonding. The study focused on shear and peel testing applied to fine line patterns less than or equal to 20 µm, as these are methods that are currently used for larger pattern testing for microelectronics and can readily be scaled down. Furthermore, each one measures the initiated or propagated adhesion strength, respectively.
1.3  Existing 90-degree peel test standards, such as IPC-TM-650 (TM 2.4.8) and JIS C 6481 (§ 5.7), can be applied to trace widths on the order of 1 mm and larger. Peel and shear tests are very common techniques used for copper trace adhesion for larger features. However, no industry standard has been established for measuring adhesion on finer traces. In the industry, some companies do have limited experience in testing trace adhesion strength for trace widths as small as 8 µm. The application of peel testing to traces below 20 µm has major challenges, including high risk of trace breakage and tool capabilities (e.g., load detection). It is beneficial to the industry to develop this Guide with best practices to ensure reliable adhesion strength measurements for smaller-scale features that can be used for process improvement, material selection, modeling, etc.
2  Scope
2.1  Adhesion measurement methods are classified by output of adhesion strength (Pa) to evaluate the resistance to deboning initiation and adhesion energy (J/m2) to measure the resistance of debonding propagation (Figure 1). The iNEMI project evaluated various potential methodologies for adhesion strength (e.g., shear) and for adhesion energy measurement (e.g., peel). This Guide will focus on peel measurement tests. Since peel and shear test equipment has traditionally expressed peel forces in grams-force (gf), this Guide has utilized gf throughout the document, however the peel forces may also be expressed in centinewtons (cN). No matter which units are utilized, the data should be captured and documented in the same units to minimize errors. The following conversion factor should be used when converting from gf to cN; 1 grams-force = 0.980665 centinewtons.
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Referenced SEMI Standards (purchase separately)
None.
NOTICE: Unless otherwise indicated, all documents cited shall be the latest published versions.

Revision History
SEMI 3D24-0726 (first published)
 

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