Thickness nondestructive

Surface Finishes. Tin-lead solder alloys (e.g., 63/37) are the most popular alloy used for surface finishes on PCBs. Other surface finishes are rapidly finding their way onto the PCBs. IPC-6012 lists more than 20 different surface finishes that are now in use for PCBs. Lead-free alloys are also appearing on PCBs. It is important to understand that the composition and type of the surface finish influence solderability. The procurement documentation must state specifications for surface finish. Methods available for analyzing the alloy composition on the plated PCB include wet analysis, atomic absorption, and x-ray fluorescence (XRF). XRF is popular because of the ease of obtaining the alloy composition and thickness nondestructively. 

XRD offers unparalleled accuracy in the measurement of atomic spacings and is the technique of choice for determining strain states in thin films. XRD is noncontact and nondestructive, which makes it ideal for in situ studies. The intensities measured with XRD can provide quantitative, accurate information on the atomic arrangements at interfaces (e.g., in multilayers). Materials composed of any element can be successfully studied with XRD, but XRD is most sensitive to high-Z elements, since the diffracted intensity from these is much lar r than from low-Z elements. As a consequence, the sensitivity of XRD depends on the material of interest. With lab-based equipment, surface sensitivities down to a thickness of -50 A are achievable, but synchrotron radiation (because of its higher intensity)... 

Ellipsometry is a very powerfiil, simple, and totally nondestructive technique for determining optical constants, film thicknesses in multilayered systems, sur ce and... 

Elastic recoil spectrometry (ERS) is used for the specific detection of hydrogen ( H, H) in surface layers of thickness up to approximately 1 pm, and the determination of the concentration profile for each species as a function of depth below the sample s surfece. When carefully used, the technique is nondestructive, absolute, fast, and independent of the host matrix and its chemical bonding structure. Although it requires an accelerator source of MeV helium ions, the instrumentation is simple and the data interpretation is straightforward. 

Each length of pipe shall be measured for conformance to wall thickness requirements. The wall thickness at any place shall not be less than the tabulated thickness minus the permissible undertolerance specified in Table 4-146. Wall thickness measurements shall be made with a mechanical caliper or with a properly calibrated nondestructive testing device of appropriate accuracy. In... 

As Table 11-1 makes clear, samples for 7-ray absorptiometry will generally have to be thicker than for the corresponding x-ray method. Accordingly, it is not surprising to find that the 7-rav technique is making rapid progress in nondestructive testing, particularly in thick-... 

This has been used, for instance, to follow the formation of palladium silicide in a silicon wafer for thicknesses up to 6nm [Vanleerdam et al., 1990]. More recently, investigation of the tails in LEIS has been used as a tool for high resolution nondestructive in-depth composition analysis of ultrathin layers [Brongersma et al., 2003] and shallow interfaces [Janssen et al., 2004]. 

TLC of larger quantities of materials (10 to 1000 mg) on thick layers (1-5mm), for the purpose of isolating separated substances for further analysis or use, is called preparative layer chromatography (PLC). Most preparative applications are carried out on 20 x 20 silica gel or alumina plates with a layer containing a fluorescent indicator to facilitate nondestructive detection. 

Geochemical analyses were conducted on unpolished thin sections 30 pm thick using micro-XRF - EDAC Eagle III mapping at the I Universite du Quebec a Chicoutimi (UQAC). Use of the micro-XRF permits analyses of major element compositions with a relatively fast, nondestructive, in situ method through points or maps. The parameters (Table 1) were selected in order to optimize the speed and quality of the results on the basis of micro-probe analyses of chlorite. 

In the distant past, measurements of the attenuation of the (3 spectrum from a newly discovered isotope were used to identify the energy of the (3 decay. Recently, the attenuation of strong sources has been used to monitor the thickness of materials during manufacturing processes. Notice that the monitoring can be continuous, nondestructive, and a physical probe does not need to touch the material being measured. 

Table I lists the weights, densities, maximum and minimum diameters, maximum thicknesses, and die orientations of the coins. The coins are identified by Crawford number (10). Because the coins have been nondestructive analyzed, their physical measurements will identify the coins at any time unless the coins are deliberately altered.

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