Procedure and results

ESEM

The environmental scanning electron microscope (ESEM) is used to test the specimen smaller than the nano scale properties. ESEM has two detectors that each gives a image for the specimen, the image quality is depending on the number electron scattered or back scattered detected by each detector. ESEM is supported by software package that device the monitor's screen into four small screens, two screens show the image of each detector and a third one shows the combination of both of the detectors' images, the last screen is showing a safety camera image which helps to avoid any direct contact between the sample and detectors the sample feeding process.

ESEM is supported by other software and hardware packages. A software package shows the chemical structure for the tested sample, the package shows on a screen the elements distribution in the sample, their percentages, and histograms that is supported with different statistical tools for advanced reports. ESEM has big variety of holders that are made from aluminium fit the samples shape and height as there are used for testing.

Specifically, in the case of applying ED7100 resistive paste on FR4 cards, ESEM helped in measuring the paste thickness of samples that are prepared using different procedures and providing topographical images about the surface after applying and curing the paste in different temperatures to avoid the consequences of paste over curing, specially as it is applied within thin thicknesses approximately between 20 um to 50 um.

Procedures of applying ED7100

The resistive paste is applied using the following procedure:

1- Applying the resistive paste manually by a flat and liner painting brush. The flat brush is used to cover the paste over most of the card area but the liner brush is used to fill the closer areas to the copper frame. This procedure succeeded to give a uniform paste surface with a thickness of 5-10 microns. The paste is cured in an oven of $160 \degree C $ for one hour.

2- Applying the paste using a fixed mechanical squeegee. In this procedure, a very flat squeegee is manufactured to be fixed on a the desired height (in micrometer) over a horizontally moving table, the paste is applied by a single trip over the FR4 card.