I addressed part of this in my recent article in the May Circuits Assembly Magazine. Paraphrasing in answer to your questions: When extracting solder from a PTH, it is important to get (nearly) all the solder out and desirable to have lead movement during the freeze cycle so that a sweat joint doesn't occur from the lead to the side of the barrel. Capillary action of wicking is NOT sufficient to overcome the same force holding solder between the edge of the lead and the barrel. You WILL have a sweat joint. Pulse extractors may/may not (1) introduce a pretty strong ESD pulse depending on (a) type (b) quality (c) condition of the pulse extractor (2) remove all/most of solder depending on (a) cleanliness (b) strength of spring (c) size of barrel (d) coverage of tip over hole (e) cooling/freezing of solder in the "remove heat & quickly get extractor tip over and release plunger" operation. It's also easy to knock a pad off or break a knee in that manual operation. Because there isn't room to move the lead around there is a good probability of forming a sweat joint to the side of the barrel. The problem with the sweat joints is that they are prone to tearing away a chunk of the barrel with the lead is forcibly removed. It may or may not interupt an internal layer connection. It may affect the ability to meet barrel fill and wetting requirements, depending on what spec you are working to (see IPC-A-610B paragraph 4.1 or J-STD-001B paragraph 9.2.5.1. Continuous vacuum extractors permit applying the heated element over the lead and nearly sealing the vacuum into the hole. Vacuum can run as long as the operator wishes to assure all the solder is extracted, even from large pad areas that might require several pulse extraction operations (each with a complete thermal cycle). With the vacuum still running, the exractor tip can be raised slightly off the pad and the lead rotated around inside the barrel ("stirred") while cool air is pulled in from the back side freezing the barrel and preventing a sweat joint from forming. All the molten solder is pulled well into the collection chamber and the tip is open and ready for immediate use. Pulse extractors have to be repeatedly cleaned. There is no thermal "shock" to be concerned about in any of these operations; rapid cooling has been shown to cause a finer grain structure which is NOT bad. Multiple and extended thermal cycles from pulse extractors and solder wick CAN introduce failure mechanisms. Jack IPC/SMTA Electronics Assembly Expo Technical Committee Meetings, Conference, Exhibits Providence RI October 24-29 More info at http://www.ipc.org Jack Crawford, IPC Project Manager - Assembly 2215 Sanders Road, Northbrook IL 60062-6135 [log in to unmask] 847-509-9700 x 393 fax 847-509-9798 >>> <[log in to unmask]> 06/05/98 12:33PM >>> All, I'm Baaack.... Got another one for you all. We occasionally have a need to rework a solder connection or an assembly by removing solder from the PTH's. Our rework/repair operators are very skilled in this type of work and use the following methods to remove solder - Solder wick, one shot solder suckers, and continuous vacuum solder suckers. Our customer is concerned about the use of the wick and the one shot solder suckers. He states that at one time they were not allowed on the high reliability standards (Mil-Std-2000) because of damage they cause. My question: What kind of damage do they cause except in the hands of an unskilled operator?? Our rework/repair success rate is phenomenal here. Our rework operators (the only ones allowed to use the solder suckers) are trained and skilled in what they do. Our customer isn't telling us we need to get rid of our solder wick and suckers, but I am sure he expects us to answer his concerns. I would consider it sufficient that we simply don't have any failures attributed to solder rework or repair, but would like a more educated answer than that. His concerns are based on a white paper he reviewed quite a number of years ago. He believes the solder sucker problems come from a thermal shock problem when ambient air is forced through a hot PTH. Some merit there, but any real-world problems? Any Insight? Thanks in advance! Steve McBride [log in to unmask] (405) 624-5281 ################################################################ 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 web site (http://jefry.ipc.org/forum.htm) 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 web site (http://jefry.ipc.org/forum.htm) for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################