Procedure and results
ESEM
The design of the environmental scanning electron microscope (ESEM) is used to test the specimen properties that are less than nono scale. 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,the aim of using ESEM is to measure the paste thickness of samples that are prepared using different procedures and it provided different topographical images for the surface after applying and curing the paste in different thicknesses and curing temperatures.
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 degrees Celsius for one hour.
2- Applying the paste using a mechanically fixed 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 in a single trip over the FR4 card to cover the plate with 10-15 layer of the resistive paste.
ESEM Images and Results
1- For the first procedure, the images below show a very thin layer of the paste is applied varies from 2 -5 provides a paste uniform surface on FR4 cards. The paste is cured using 160 degree Celsius oven for an hour without causing any cracks or humps on the surface.