The metal thickness of surface finish is an important consideration when plating on microelectronics. Metal finish thickness should comply with specification requirements to prevent serious reliability concerns. The thickness of metallic coatings is routinely determined by X-ray fluorescence (XRF) spectrometry. For conventional XRF instrumentation, typical focal spot sizes at the sample surface range in diameter from several hundred micrometers up to several millimeters. Micro- XRF focuses or collimates the X-ray beam to significantly smaller spot sizes, ranging from ~30 µm to 2 mm, thus obtaining a representative average of layer properties both at the surface and in-depth layers. This is a critical property for application in semiconductor industry where feature size is becoming progressively smaller. This work describes how a mid-range cost conventional XRF tool can be utilized for small spot size thickness measurement with the addition of a 0.25 mm diameter collimator.

The Directive 2002/95/EC (referred as ROHS) of the European Parliament and of the Council restricts the use of certain hazardous substances in electrical and electronic equipment. This article reports on a fast and inexpensive methodology for rapidly screening entire electronic assemblies that acts as a high-level screen for obvious ROHS violations. Using this methodology, this lab has been able to check entire product lines for basic ROHS compliance and has identified many cases where vendors needed to be informed of ROHS violations before a product could be certified as ROHS compliant. Four tests are employed. Each of them is described, along with the basic theory behind the test: pre-screening with x-ray fluorescence spectroscopy and electron dispersion spectroscopy; detection and identification of polybrominated biphenyl ethers using gas chromatography - mass spectrometry; and chromium 6 colorimetric testing based on diphenylcarbazide.