IEC 62047-38-2021 pdf free download – Semiconductor devices — Micro- electromechanical devices Part 38: Test method for adhesion strength of metal powder paste in MEMS interconnection.
5 Testing method and test apparatus
5.1Test principle
The test is performed by applying the contact load on the metal powder paste using a cleanedglass lens with a few millimetre curvature,and then by detaching the lens from the paste toevaluate the adhesion strength of the paste. A test example can be found in Annex A. Duringthe loading process, the metal powder in the paste is deformed by the contact with the lensand the contact area between the lens and the metal powder is formed.The changes in thecontact area are recorded by an optical microscope and cCD camera. The contact area iscalculated by analyzing the recorded images after the test.During the unloading process, thecontact load is decreased and a pulling force is applied on the interface between the lens andthe paste due to the adhesion between them.After the maximum pulling force reaches,thecontact area is rapidly decreased and the lens is completely separated from the paste.Theadhesion strength of the metal powder paste can be evaluated by dividing the maximumpulling force with the contact area between the lens and the metal powder measured beforethe unloading process.The lens can be coated with thin metal films such as Au and Al forsimulating the electrode materials of MEMS.
5.2Test apparatus
The test machine is shown in Figure 2.The glass lens is fixed on the top of the chamber byclamping and the metal powder paste test piece is installed on the sample stage.The testpiece is moved toward the glass lens by moving the z-axis motorized stage for the loadingprocess and then is separated from the lens by moving down the z-axis stage for theunloading process. During the test,the force is measured by loadcell, and optical images ofthe contact area are recorded using an optical microscope and cCD camera. The contactarea images shall be recorded at a speed larger than 30 Hz using a camera with amicroscope objective of 20x or more.
5.3Test procedure
The test procedure is as follows:
a) install a test piece on the sample stage and start to record loadcell output signal andoptical microscope images;
b) apply a contact load to the test piece by moving the Z-axis stage. This is a loading
process. The test piece is made contact with the glass lens fixed on the chamber andcompressed, so the contact area between the lens and paste is formed;
c) hold the contact for a holding time of a few seconds. This is for stabilizing the contact interface;
d) separate the test piece from the lens by moving down the z-axis stage with a separation speed. This is the unloading process;
e) after testing，remove the test piece from the test machine with caution. lf possible, preserve the test piece for investigation using electron and optical microscopes.
5.4 Test environment Because the physical properties of metal powder paste are temperature sensitive, fluctuations in temperature during the test shall be controlled to be less than ± 2 °C. The adhesion of the glass lens can be sensitive to humidity; thus, the change in relative humidity (RH) in the testing laboratory shall be controlled to be less than ± 5 % RH for such materials. Because the adhesion test is sensitive to contaminants such as air-borne particles and dust, the test should be conducted in a cleanroom of class 1 000 or 1 0 000.IEC 62047-38 pdf download.