The Analysis Of Cold Adhesion Phenomena For The Micro-electromagnetic Relay Contacts And Research Of Its Control Strategies

This paper analyses the cold adhesion failure phenomenon happens in the procedure of the 1JL(1Z,1A contact load),2JL(2Z,0.5A contact load)?2JB(2Z,2A contact load)?2JT(2Z.5A contact load)micro-electromagnetic relays9(MEMR9)assemble,mechanical cycles,high temperature and low temperature run-in,vibration and life test of low level load.It's affirmed that the surface quality of gold-plated contact,internal moisture value,stiffness characteristics of the contacts are the main factors in MEMR' cold adhesion failure.By researching the co-relations between the three main factors to MEMR' cold adhesion failure,The control strategies of the MEMR' contact cold adhesion failure during the product's manufacture were found?First,The tests in order to remove the contacts gold finger plating of 1JL and 2JL relays that the cold adhesion have occurred have been done,The test result proves that that the contacts surface quality of gold-plated is one of the leading factor in the cold adhesion.In order to obtain the suitable quality of contacts surface gold-plated,investigation on the technologies of pulse electroplating,vibratory electroplating and the gold-Co(cobalt)plating were taken.The results shows that the technology of DC-pulse electroplating and gold-Co(cobalt)plating would improve the contacts gold-Co plating's hardness and consistency.The contacts that were plated gold-Co by this technology have been assembled in the micro-electromagnetic relays,The contacts cold adhesion stop occurring during all of the manufacturing procedures in the micro-electromagnetic relays,which show the obvious effect of the cold adhesion by these technologies.Second,The phenomenon was researched that the cold adhesion failure percentage would grow up during 2JB relays' low-level load run-in and the high frequency vibrations tests when the value of its' internal moisture is small.The results of the research shows that when the value of the internal moisture in the 2JB relay was no more than 1000ppm the contacts cold adhesion failure percentage would sharply grow up.Research show that when the value of the moisture in the 2JB relay was between 1000ppm and 3000ppm,the contacts cold adhesion has been suppressed.The factors which affect the ralue of internal moisture in the relays have been researched,and obtain the effective technologies that could make the value of the internal moisture between 1000ppm and 3000ppm in the micro-electromagnetic relays.Third,By analyze the cold adhesion failure which occurred in the 1JL relay,it was found that its contact bounce time was longer than the no cold adhesion relays,which indicates there exists a bigger slip displacement between the cold adhesion contacts,the big slip displacement would increase the possibility of the cold adhesion.The research on a collision physical model between the contact movable and the normally open contact draw a conclusion when the stiffness value of the normally open contact and the movable contact have been changed for match,and decrease the slip displacement of collision,which would decrease the possibility of the cold adhesion.Thus,according to the conclusion,the configuration of the 1JL relay's normally open contact and normally close contact have been changed for match,that decrease the slip displacement of collision between the movable contact and the normally open contact,the result of the test show that the 1 JL relay's contact bounce time smaller than before.Last,The three technologies above have been used in the 1JL relay manufacture,and there were no contacts cold adhesion during the manufacture and the test procedures in the six consecutive batches products.The results validated effectiveness of control strategies on cold adhesion of the micro-electromagnetic relays by this research.