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Category: Scratch Testing | Cohesive Failure


Adhesion Properties of Gold Coating on Quartz Crystal Substrate


Adhesion Properties of Gold Coating

on Quartz Crystal Substrate

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The Quartz Crystal Microbalance (QCM) is an extremely sensitive mass sensor capable of making precise measurements of small mass in the nanogram range. QCM measures the mass change on the surface through detecting variations in resonance frequency of the quartz crystal with two electrodes affixed to each side of the plate. The capacity of measuring extreme small weight makes it a key component in a variety of research and industrial instruments to detect and monitor the variation of mass, adsorption, density, and corrosion, etc.


As an extremely accurate device, the QCM measures the mass change down to 0.1 nanogram. Any mass loss or delamination of the electrodes on the quartz plate will be detected by the quartz crystal and cause significant measurement errors. As a result, the intrinsic quality of the electrode coating and the interfacial integrity of the coating/substrate system play an essential role in performing accurate and repeatable mass measurement. The Micro scratch test is a widely used comparative measurement to evaluate the relative cohesion or adhesion properties of coatings based on comparison of the critical loads at which failures appear. It is a superior tool for reliable quality control of QCMs.


In this application, the NANOVEA Mechanical Tester, in Micro Scratch Mode, is used to evaluate the cohesive & adhesive strength of the gold coating on the quartz substrate of a QCM sample. We would like to showcase the capacity of the NANOVEA Mechanical Tester in performing micro scratch tests on a delicate sample with high precision and repeatability.



The NANOVEA PB1000 Mechanical Tester was used to perform the micro scratch tests on a QCM sample using the test parameters summarized below. Three scratches were performed to ensure reproducibility of the results.

LOAD TYPE: Progressive


0.01 N


30 N



2 mm/min


2 mm


The full micro scratch track on the QCM sample is shown in FIGURE 1. The failure behaviors at different critical loads are displayed in FIGURE 2, where critical load, LC1 is defined as the load at which the first sign of adhesive failure occurs in the scratch track, LC2 is the load after which repetitive adhesive failures take place, and LC3 is the load at which the coating is completely removed from the substrate. It can be observed that little chipping takes place at LC1 of 11.15 N, the first sign of coating failure. 

As the normal load continues to increase during the micro scratch test, repetitive adhesive failures occur after LC2 of 16.29 N. When LC3 of 19.09 N is reached, the coating completely delaminates from the quartz substrate. Such critical loads can be used to quantitatively compare the cohesive and adhesive strength of the coating and select the best candidate for targeted applications.

FIGURE 1: Full micro scratch track on the QCM sample.

FIGURE 2: Micro scratch track at different critical loads.

FIGURE 3 plots the evolution of friction coefficient and depth that may provide more insight in the progression of coating failures during the micro scratch test.

FIGURE 3: Evolution of COF and Depth during the micro scratch test.


In this study, we showcased that the NANOVEA Mechanical Tester performs reliable and accurate micro scratch tests on a QCM sample. By applying linearly increased loads in a controlled and closely monitored fashion, the scratch measurement allows users to identify the critical load at which typical cohesive and adhesive coating failure occurs. It provides a superior tool to quantitatively evaluate and compare the intrinsic quality of the coating and the interfacial integrity of the coating/substrate system for QCM.

The Nano, Micro or Macro modules of the NANOVEA Mechanical Tester all include ISO and ASTM compliant indentation, scratch and wear tester modes, providing the widest and most user friendly range of testing available in a single system. NANOVEA‘s unmatched range is an ideal solution for determining the full range of mechanical properties of thin or thick, soft or hard coatings, films and substrates, including hardness, Young’s modulus, fracture toughness, adhesion, wear resistance and many others.

In addition, an optional 3D non-contact profiler and AFM module are available for high resolution 3D imaging of indentation, scratch and wear track in addition to other surface measurements, such as roughness and warpage.


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Wear and Scratch Evaluation of Surface Treated Copper Wire

Wear and Scratch Evaluation of Surface Treated Copper Wire

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Importance of Wear and Scratch Evaluation of Copper Wire

Copper has a long history of use in electric wiring since the invention of the electromagnet and telegraph. Copper wires are applied in a wide range of electronic equipment such as panels, meters, computers, business machines, and appliances thanks to its corrosion resistance, solderability, and performance at elevated temperatures up to 150°C. Approximately half of all mined copper is used for manufacturing electrical wire and cable conductors.

Copper wire surface quality is critical to application service performance and lifetime. Micro defects in wires may lead to excessive wear, crack initiation and propagation, decreased conductivity, and inadequate solderability. Proper surface treatment of copper wires removes surface defects generated during wire drawing improving corrosion, scratch, and wear resistance. Many aerospace applications with copper wires require controlled behavior to prevent unexpected equipment failure. Quantifiable and reliable measurements are needed to properly evaluate the wear and scratch resistance of the copper wire surface.

Measurement Objective

In this application we simulate a controlled wear process of different copper wire surface treatments. Scratch testing measures the load required to cause failure on the treated surface layer. This study showcases the Nanovea Tribometer and Mechanical Tester as ideal tools for evaluation and quality control of electric wires.

Test Procedure and Procedures

Coefficient of friction (COF) and wear resistance of two different surface treatments on copper wires (Wire A and Wire B) were evaluated by the Nanovea tribometer using a linear reciprocating wear module. An Al₂O₃ ball (6 mm diameter) is the counter material used in this application. The wear track was examined using Nanovea’s 3D non-contact profilometer. Test parameters are summarized in Table 1.

A smooth Al₂O₃ ball as a counter material was used as an example in this study. Any solid material with different shape and surface finish can be applied using a custom fixture to simulate the actual application situation.

Nanovea’s mechanical tester equipped with a Rockwell C diamond stylus (100 μm radius) performed progressive load scratch tests on the coated wires using micro scratch mode. Scratch test parameters and tip geometry are shown in Table 2.

Results and Discussion

Wear of copper wire: Figure 2 shows COF evolution of the copper wires during wear tests. Wire A shows a stable COF of ~0.4 throughout the wear test while wire B exhibits a COF of ~0.35 in the first 100 revolutions and progressively increases to ~0.4.

Figure 3 compares wear tracks of the copper wires after tests. Nanovea’s 3D non-contact profilometer offered superior analysis of the detailed morphology of wear tracks. It allows direct and accurate determination of the wear track volume by providing a fundamental understanding of the wear mechanism. Wire B’s surface has signi¬ficant wear track damage after a 600-revolution wear test. The profilometer 3D view shows the surface treated layer of Wire B removed completely which substantially accelerated the wear process. This left a flattened wear track on Wire B where copper substrate is exposed. This may result in significantly shortened lifespan of electrical equipment where Wire B is used. In comparison, Wire A exhibits relatively mild wear shown by a shallow wear track on the surface. The surface treated layer on Wire A did not remove like the layer on Wire B under the same conditions.

Scratch resistance of the copper wire surface: Figure 4 shows the scratch tracks on the wires after testing. The protective layer of Wire A exhibits very good scratch resistance. It delaminates at a load of ~12.6 N. In comparison, the protective layer of Wire B failed at a load of ~1.0 N. Such a significant difference in scratch resistance for these wires contributes to their wear performance, where Wire A possesses substantially enhanced wear resistance. The evolution of normal force, COF, and depth during the scratch tests shown in Fig. 5 provides more insight on coating failure during tests.


In this controlled study we showcased the Nanovea’s tribometer conducting quantitative evaluation of wear resistance for surface treated copper wires and Nanovea’s mechanical tester providing reliable assessment of copper wire scratch resistance. Wire surface treatment plays a critical role in the tribo-mechanical properties during their lifetime. Proper surface treatment on Wire A significantly enhanced wear and scratch resistance, critical in the performance and lifespan of electrical wires in rough environments. Nanovea’s tribometer offers precise and repeatable wear and friction testing using ISO and ASTM compliant rotative and linear modes, with optional high temperature wear, lubrication, and tribo-corrosion modules available in one pre-integrated system. Nanovea’s unmatched range is an ideal solution for determining the full range of tribological properties of thin or thick, soft or hard coatings, films, and substrates.

Understanding Coating Failures using Scratch Testing


Surface engineering of materials plays a significant role in a variety of functional applications, ranging from decorative appearance to protecting the substrates from wear, corrosion and other forms of attacks. An important and overriding factor that determines the quality and service lifetime of the coatings is their cohesive and adhesive strength.

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Scratch Resistance of Cellphone Screen Protectors

Scratch Resistance of Cellphone Screen Protectors

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Importance of Testing Screen Protectors

Although phone screens are designed to resist shattering and scratching, they are still susceptible to damage. Daily phone usage causes them to wear and tear, e.g. accumulate scratches and cracks. Since repairing these screens can be expensive, screen protectors are an affordable damage prevention item commonly purchased and used to increase a screen’s durability.

Using the Nanovea PB1000 Mechanical Tester’s Macro Module in conjunction with the acoustic emissions (AE) sensor, we can clearly identify critical loads at which screen protectors show failure due to scratch1 testing to create a comparative study between two types of screen protectors.

Two common types of screen protector materials are TPU (thermoplastic polyurethane) and tempered glass. Of the two, tempered glass is considered the best as it provides better impact and scratch protection. However, it is also the most expensive. TPU screen protectors on the other hand, are less expensive and a popular choice for consumers who prefer plastic screen protectors. Since screen protectors are designed to absorb scratches and impacts and are usually made of materials with brittle properties, controlled scratch testing paired with in-situ AE detection is an optimal test setup for determining the loads at which cohesive failures (e.g. cracking, chipping and fracture) and/or adhesive failures (e.g. delamination and spallation) occur.

Measurement Objective

In this study, three scratch tests were performed on two different commercial screen protectors using Nanovea’s PB1000 Mechanical Tester’s Macro Module. By using an acoustic emissions sensor and optical microscope, the critical loads at which each screen protector showed failure(s) were identified.

Test Procedure and Procedures

The Nanovea PB1000 Mechanical Tester was used to test two screen protectors applied onto a phone screen and clamped down to a friction sensor table. The test parameters for all scratches are tabulated in Table 1 below.

Results and Discussion

Because the screen protectors were made of a different material, they each exhibited varying types of failures. Only one critical failure was observed for the TPU screen protector whereas the tempered glass screen protector exhibited two. The results for each sample are shown in Table 2 below. Critical load #1 is defined as the load at which the screen protectors started to show signs of cohesive failure under the microscope. Critical load #2 is defined by the first peak change seen in the acoustic emissions graph data.

For the TPU screen protector, Critical load #2 correlates to the location along with the scratch where the protector began to visibly peel off the phone screen. A scratch appeared on the surface of the phone screen once Critical load #2 was surpassed for the remainder of the scratch tests. For the Tempered Glass screen protector, Critical load #1 correlates to the location where radial fractures began to appear. Critical load #2 happens towards the end of the scratch at higher loads. The acoustic emission is a larger magnitude than the TPU screen protector, however, no damage was done to the phone screen. In both cases, Critical load #2 corresponded to a large change in depth, indicating the indenter had pierced through the screen protector.


In this study we showcase the Nanovea PB1000 Mechanical Tester’s ability to perform controlled and repeat-able scratch tests and simultaneously use acoustic emission detection to accurately identify the loads at which adhesive and cohesive failure occur in screen protectors made of TPU and tempered glass. The experimental data presented in this document supports the initial assumption that Tempered Glass performs the best for scratch prevention on phone screens.

The Nanovea Mechanical Tester offers accurate and repeatable indentation, scratch, and wear measurement capabilities using ISO and ASTM compliant Nano and Micro modules. The Mechanical Tester is a complete system, making it the ideal solution for determining the full range of mechanical properties of thin or thick, soft or hard coatings, films, and substrates.

Multi Scratch Automation of Similar Samples using the PB1000 Mechanical Tester

Introduction :

Coatings are widely used in various industries because of their functional properties. A coating’s hardness, erosion resistance, low friction, and high wear resistance are just some of the many properties that make coatings important. A commonly used method to quantify these properties is scratch testing, this allows for a repeatable measurement of a coating’s adhesive and/or cohesive properties. By comparing the critical loads at which failure occurs, the intrinsic properties of a coating can be evaluated.

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A BETTER Look at Polycarbonate Lens

A BETTER Look at Polycarbonate Lens Learn more
Polycarbonate lenses are commonly used in many optical applications. Their high impact resistance, low weight, and cheap cost of high-volume production makes them more practical than traditional glass in various applications [1]. Some of these applications require safety (e.g. safety eyewear), complexity (e.g. Fresnel lens) or durability (e.g. traffic light lens) criteria that are difficult to meet without the use of plastics. Its ability to cheaply meet many requirements while maintaining sufficient optical qualities makes plastic lenses stand out in its field. Polycarbonate lenses also have limitations. The main concern for consumers is the ease at which they can be scratched. To compensate for this, extra processes can be carried out to apply an anti-scratch coating. Nanovea takes a look into some important properties of plastic lens by utilizing our three metrology instruments: Profilometer, Tribometer, and Mechanical Tester.   Click to Read More!

Identifying Cohesive Failure of Screen Protectors with Acoustic Emission

In today’s age of information, handheld electronic devices are extremely common amongst consumers.  These portable multifunctional devices, however, can be quite expensive. To protect the fragile components, such as the glass interface, screen protectors can be used. How effective are the screen protectors? Using Nanovea’s Mechanical Tester’s Micro Module with an acoustic emission attachment, we can clearly identify critical loads at which the screen protector fails.

Identifying Cohesive Failure of Screen Protectors with Acoustic Emission

Mechanical Properties of Silicon Carbide Wafer Coatings

Understanding the mechanical properties of silicon carbide wafer coatings is critical. The fabrication process for microelectronic devices can have over 300 different processing steps and can take anywhere from six to eight weeks. During this process, the wafer substrate must be able to withstand the extreme conditions of manufacturing, since a failure at any step would result in the loss of time and money. The testing of hardness, adhesion/scratch resistance and COF/wear rate of the wafer must meet certain requirements in order to survive the conditions imposed during the manufacturing and application process to insure a failure will not occur.

Mechanical Properties of Silicon Carbide Wafer Coatings

Micro Scrape Test Of Polymeric Coating

Scratch testing has developed to be one of the most widely applied methods to evaluate the cohesive and adhesive strength of the coatings. The critical load, at which a certain type of coating failure occurs as the applied load progressively increases, is widely regarded as a reliable tool to determine and compare the adhesive and cohesive properties of the coatings. The most commonly used indenter for scratch testing is the conical Rockwell diamond indenter. However, when the scratch test is performed on the soft polymeric coating deposited on a brittle substrate such as silicon wafer, the conical indenter tends to plough through the coating forming grooves rather than creating cracks or delamination. Cracking of the brittle silicon wafer takes place when the load further increases. Therefore, it is vital to develop a new technique to evaluate the cohesion or adhesion properties of soft coatings on a brittle substrate.

Micro Scrape Test Of Polymeric Coating

ASTM D7187 Temperature Effect Using Nanoscratching

ASTM D7187, the resistance of the paint to scratch and mar plays a vital role in its end use. Automotive paint susceptible to scratches makes it difficult and costly to maintain and repair. Different coating architectures of the primer, basecoat, and clearcoat have been developed to achieve the best scratch/mar resistance. Nanoscratch testing has been developed as a standard test method to measure the mechanistic aspects of scratch/mar behavior of paint coatings as described in ASTM D7187. Different elementary deformation mechanisms, namely elastic deformation, plastic deformation and fracture, occur at different loads during the scratch test. It provides a quantitative assessment of the plastic resistance and fracture resistance of the paint coatings.

ASTM D7187 Temperature Effect Using Nanoscratching

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