Zhangkun- Sometimes "dry test" refers to the nature of the physical contact. If the probes making the electrical contact are just touching the circuit element, it is called a "dry contact". There is a lot of physics associated with making reliable dry contacts in electrical test. This is the nature of testing all semiconductor packages and bare die. Needle and Form Factor MEMs probes make a dry contact to the pads on the die. Spring probes make a dry contact to the pads or balls on the package. In dry contacts, contact resistance can play a dominate role. With gold on gold and more than 40 gm of force, the dry contact resistance can be a few milliOhms. But with Tungsten on Al pads, the dry contact resistance can be 2 ohms. With probes tips on solder pads or balls, the dry contact resistance can be 5-50 mOhms, depending on the oxide at the interface. Designing the probe tip geometry and metallurgy for reliable, reproducible dry contacts for hundreds of thousands of tests is a challenge. There's lots of subtle physics at the interface. A non dry test would use either a high shear, sliding, pin in box type connection, typically between gold surfaces, or a solder connection. --eric ************************************** Dr. Eric Bogatin, President Bogatin Enterprises, LLC Signal Integrity Online Training Next Public class: Oct 11, 12, 2006, San Jose, CA Mastering Signal Integrity Characterization Techniques 26235 w 110th terr Olathe, KS 66061 v: 913-393-1305 f: 913-393-0929 c:913-424-4333 e:eric@xxxxxxxxxxxxxxx <http://www.BeTheSignal.com> www.BeTheSignal.com **************************************** Msg: #1 in digest Date: Sat, 26 Aug 2006 14:47:59 +0800 From: Zhangkun <zhang_kun@xxxxxxxxxx> Subject: [SI-LIST] What is the difference between "non dry circuit test" and Dear all Currently, I am using MICRO-OHMMETER of Keithly. There are two elements, "non dry circuit test" and "dry circuit test". What is the difference between these two elements? Best Regards Zhangkun 2006.8.26 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu