If an organization relies on accurate coating thickness measurements in its quality control process, it is likely to be familiar with ED-XRF technology.
Although new advances in XRF analyzers have broadened the range of applications for the technology, one of the common uses remains measuring the thickness of metallic coatings. From basic single layer measurement needs to complex coating systems including multilayer measurement, thin film and plating solution analysis, XRF will provide a non-destructive, fast and relatively inexpensive method to obtain highly accurate measurement results.
When considering an XRF analyzer for plating thickness applications, potential users have many options in general technology to consider. X-ray fluorescence analyzers are now available with three different types of detection systems - ratiometric counting Detector, PIN diode Detector (Si-PIN) or silicon drift detection technology (SDD). Each method has advantages depending on the type of application, the required measurement speed, and how thin or thin the measurement results are. Additionally, there are machines that can use XRF tubes, ranging in power from 4 watts to 400 watts, and the list of options goes on and on. A better way to determine what you need is to learn about the application and contact an XRF sales company. Tell them which materials to test and the range of thickness values.
All XRF analyzers require periodic recalibration or adjustment due to changes in electronic components. When enough drift occurs, the instrument may not be able to accurately adjust accordingly to compensate for the difference. The importance of using quality reference standards for the regular verification of instrument accuracy cannot be overemphasized. Daily accuracy verification should be performed using a reference standard prior to testing the product. This is especially true for systems based on empirical calibration methods. Users need to look for a professional X-ray fluorescence technology standard certification standard laboratory, and provide certified traceable standards.
When purchasing XRF calibration standards for thickness analysis, know which format to use since there are two styles to choose from: plated or foil. These two formats are commonly used throughout the industry and provide reliable results. When determining a good fit, consider the standard XRF analyzer model (including collimator sizes available for the application) that will be used. This model is important because standards can be installed on different platforms and software algorithms vary from brand to brand, so the same calibration curve may require different ranges and numbers of standards from different analyzers. In addition to the XRF model, the composition of interest and target thickness would be a factor in a well-standard approach.
foil standard
This style of reference standard is the common method and comes with a foil attached to a stainless steel foil holder of a desired material and thickness. The foil is then temporarily fixed on top of a plastic sheet containing the desired substrate (also known as infinity). When a range of thicknesses is required, the user will have multiple foils of different thicknesses spanning the desired range, and will switch out the top layer when calibrating the various thickness levels.
When multi-layer thickness measurement is the goal, the user stacks multiple foils to an infinite length. An example is Au/Ni/Cu. The user will select the appropriate thickness of gold (Au) foil, nickel (Ni) thickness and copper (Cu) substrate, and then stack them with gold on copper.
Advantages Aluminum Foil
Versatility: Foil standards can be placed on any desired substrate, increasing the range of applications.
Multi-layer flexibility: They are often stacked together to obtain a reliable multi-layer analysis method.
Available Curves: When using stacked foils for multilayer analysis, there are basically three useful calibration curves, two single layer curves and one multilayer curve. Essentially, one of the monolayers is the first coating and can be used to monitor the process in the coating.
Disadvantages of foilFragile: While more versatile, the foil itself is fragile and requires careful handling to avoid punctures. In general, aluminum foil standards are not suitable for everyday use or in environments where they may be exposed to a lot of dirt, as they cannot be cleaned.
Coating standardDurability: Compared to foil, plated standards tend to be more durable and withstand heavy handling. However, they are still easily damaged when the surface being measured comes into contact with an object. Even user-touched surfaces can be damaged by environmental contamination or oils from the user's hands.
EXTENDED LIFE: Fortunately, if scratches or damage happen to your plating standard, all is not lost. In most cases the standard can be polished with a fine polish and expressed to reflect the new lower value.
Disadvantages of PlatingNo versatility: to permanently fix the coating on the substrate, the user needs to have different plating standards for each thickness and substrate combination.
Possible Variation: Certain plated metals such as lead, gold, silver, and tin (to name a few) have been reported to migrate over time and thus may alter the thickness of the reference material. This change takes a long time but can be monitored through reference standards certified annually by accredited laboratories.
Regardless of the calibration standard used, periodic certification is recommended. This is usually an annual service and is recommended even if it is not required to maintain the organization's certification. Routine certification of standards is recommended as their condition may change over time due to corrosion, intermetallic migration, fouling and handling. This can lead to discrepancies between actual coating thicknesses and standard certified values and can lead to inaccurate measurements that can negatively impact the organization.
While routine certification of XRF analyzers is also recommended, it is often noted that reference standard certification is more important for systems to achieve sustained performance. Most accredited standards laboratories will have a tracking system in place to monitor certification expiration dates and communicate with clients in advance to help ensure important certifications are not missed.- Most XRF instruments are only as accurate as the standards used for calibration. In order to control a process, there absolutely needs to be a way to verify the accuracy of the machine. If the inspection system does not currently exist, one needs to be added. Don't lose money by losing customers because the product is gold plated and don't lose money because of gold plated material.
These are formed by electroplating a specific thickness of the desired material onto a permanent substrate. When a series of standards is required, the user will have standards of several different thicknesses to span the desired calibration range (one piece each thickness of layer and substrate). So if a user measures gold on nickel in the 50u" to 300u" range, they might have a three piece gold plating kit of 50u", 150u" and 300u" on the nickel base material. Also include a "clean" Unlimited single piece (nickel in this case), making it a set of four.
Gold Plated Standard Benefits
