Dhawan, So, you try to skip all research headaches and jump right into the muddy water. Check Enthone and kester web sites. They have many excellent technical articles written on the subject of OSP's - www.kester.com - www.enthone-omi.com Also check July 1997 & August 1998 editions of Printed Circuit Fabrication for OSP and electroless immersion gold/nickel articles. If you don't have them, name your fax, I will try my best to fax them on Monday. If you plan to use no-clean in near future, I recommend immersioin gold/nickel finish coating. This is a drop-in replacement for HASL boards. You don't have to fiddle around with the existing process. Wettibilty of gold is far superior than HASL and solder joint fillet formation is far better. One major solder appearance change from HASL is all solder joints are dull-looking. Solder joint embrittlement due to too much gold content (usaully 3/5% more) are unfounded. Immersion gold/nickel provides consistent gold thickness of 1um. One problem you might encounter (depending upon who your board vendor is for immersion gold) is gold fall-out around SMT pads. This could cause shorts especially for QFP pads. Gold fall-out (fine gold dusts) is usually caused by too much plating. The problem can easily fixed by fine-tuning gold plating process by the board vendor. OSP coated board provides the same or better flatness than gold. But the manufacturing process requires some fiddlings and the handling of boards are more sensitive. It provides a superior solder joint shininess and less intermetalic and cold joints. This is because there are no oxidized and contaminated solder from HASL. Some of issues you might tackle when using OSP coated boards: Watch out how many heat cycles a product go thru, and boards should be assembled and completed within a limited time. Don't leave them out on the floor too long when they have to go thru next assembly and heat cycle. I guess I am talking about a few days.. Non or de-wetting could be a problem if not processed within a given time. Cleaning of mis-printed board could cause non-wetting problem as well. This tends to remove a fraction of OSP coating. 0.35um thickness is indeed thin. Solder filling of thru-hole in the wave is another issue. It will never get filled fully the way HASL coating. Usually solder wicks up to about 50% or 75% of hole. This is acceptable under IPC 600 class 2 and 3. You also have to deal with exposed copper area. I don't think it will be a quality issue. Training of assembly people for the proper handling of OSP is also important. More active flux (Water-soluble) works better with OSP, and there are no-clean flux formulated for OSP. I tested one no clean flux type but the result isn't better than the one I am using. I guess I am telling OSP is not a drop-in replacement for HASL regards Matthew Park SMT Manufacturing Engineer NII-Norsat International Inc. Surrey, BC. sorry I can not help you with surface flatness. I don't think there is any guideline for that. But the pad surface level should be within a twice thickness of leaded pin for QFPs. >>> "Dhawan, Ashok" <[log in to unmask]> August 7, 1998 1:48 pm >>> For fine pitch devices 15.7 mils and small chips 0603 ,do we have any IPC standard stating that what kind of surface leveliing /planarity required for placement of FPDs and 0603/0402 chips.Even accurate placement can go offline once the surface is not flat. the situation is worse when we are trying to place 0603 components on glue dots. Also, there are no. of options for HAl alternatives . We are comparing gold immersion and OSPs.Our circuit boards are having fine pitch devices extendable to 12 mils QFPs and 50/60 mils BGAs and chips down to 0402 package size.We also intend to implement No-Clean process in near future. We have limited experience with Au immersion/Ni electroless and OSPs. What are views of experts who had some point of time decided course of action. What you think we go for?We want to go for process where we do not have to modify /readjust our current process based on water soluble soldering. Pro and Cons? Not to mention that I consider technet as my vital tool for problem solving. I will appreciate comments on this asap as I am running out of time and our process meeting is scheduled on Monady morning. thanks ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################ ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################