Right now, I feel like a moth circling around the blue light of a bug zapper. I know I shouldn't go near the light, I know I will get zapped, but I just can't help myself..................... Looking for a simple definition of SIR is like looking for a simple definition of reliability. Good luck finding one that everyone agrees with other than in the broadest possible terms. Many of the IPC SIR and Electromigration task group meetings start with a good 20-30 minutes on arguing about terms. Longer if Brother Brian Ellis attends. Far longer if Phil Wittmer gets into the act. And if I'm involved, God knows when you get out of the meeting. Conceptually, surface insulation resistance refers to a materials system characteristic. In theory, you measure the resistance between two conductors, such as fingers of a comb pattern, across the intervening surface. The resulting measurement is the surface insulation resistance. In reality, you have several parallel resistances. A resistance across the surface, such as through a flux residue, a resistance through the bulk of the resin, perhaps a resistance through the bulk of solder mask if a mask fills the space. Hence the existing wording in 9201. I would direct your attention to an article I wrote in the November 2000 Process Rx column that talks about all of the parallel resistances and capacitances you need to consider if you are truly going to characterize the system. I can make that column available to anyone who wants it. Ever look at a comb pattern? Two conductors separated by a dielectric material. Sounds like a capacitor to me. A metrologist would be a good person to consult in SIR testing. They always ask, are you measuring what you think you are measuring? Further confusing the issue is how SIR testing, as a term, has been used. I think of SIR as a materials system characteristic. I can measure SIR at ambient, at hot/dry conditions, at hot/humid conditions etc. I can look at how SIR changes with changes in environment. So, SIR and SIR testing mean subtly different things. The 9201 handbook is starting its revision cycle this spring and will be headed up by Curt Lustig of Morton Specialty Chemicals. If there is something you want better explained, now is the time to say so. Is SIR considered an alternative to ionic cleanliness? Maybe. Depends on your criteria. Depends on who is doing the testing (in either case). Depends on your definition of cleanliness. Depends on what ionic cleanliness test you are talking about. Is there any correlation between the two? A very loose one. As ionic residues increase, the SIR levels will decrease, but a good scientific correlation? Nope. It also depends on what measures of ionic cleanliness you are talking about. If you are talking about SIR vs. ROSE, the correlation is very very broad and loose. If you are talking about SIR vs. an individual ion as measured by ion chromatography, the correlation is a little more scientific, but not by much. I suggest you go back over the archives of Technet, searching on SIR, electromigration and Ellis. Brian has given some wonderful dissertations on the physics of the measurement and what goes on in electromigration, far better than I can. Must be the sunshine in Cyprus or the clean air in Switzerland. What other benefits are available with SIR? Well, it helps out the local economies near test labs...... Personally, if I had a choice between ionic contamination testing and SIR testing (assuming both competently done), I would choose the SIR testing as the bottom line of whether a residue was harmful. Ion chromatography is a good tool for determining what residues are present and in what amounts, but past clients still come back with the "so what" question. What does 5 micrograms of chloride mean to me? On the other hand, if you had SIR testing, you can show no detrimental leakage currents under humid conditions, no corrosion, no metal migration, which are the big factors in figuring out electrochemical reliability. People often have a greater comfort with passing SIR than they do with passing ROSE tests. Of course, SIR testing takes a while and so it is best to do both ion chromatography and SIR at the same time so you can determine the correlation between SIR performance and cleanliness levels for troubleshooting the process later. Enough for now. Doug Pauls Rockwell Collins Thats for starting the conversation. I have been trying to find time to look into SIR. Is it considered an alternative to ionic cleanliness? If so, is there any correlation to ug/sq. cm. We have some medical implant customers, that are concerned about any conductive surface contaminate. What other benefits are available with SIR? >>> [log in to unmask] 04/27/01 10:17AM >>> OK, let's see what I can stir up today. :) I am looking for a clear, succinct definition of surface insulation resistance. If I look in IPC-9201 "Surface Insulation Resistance Handbook", I don't find what I am looking for. (Sorry, Joe, Doug et al). What I find on page 2, section 2.1, Definitions is the following: "It represents the electrical resistance between two electrical conductors separated by some dielectric material(s). This property is loosely based on the concept of sheet resistance, (see ASTM-D-263), but also contains elements of bulk conductivity, leakage through electrolytic contaminants, multiple dielectric and metallization materials and air." Whew! Any takers? Hmmm? regards, Bev Christian Research in Motion --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 --------------------------------------------------------------------------------- --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 --------------------------------------------------------------------------------- --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------