Wee: A fused Sn/Pb board is normally covered by soldermask. If not you could obviously have a real mess at wavesolder. The problem with a conventionally built fused Sn/Pb board i.e. circuitry is fused Sn/Pb, is that during reflow and/or wavesolder the Sn/Pb melts under the mask. This can cause adhesion failure of the soldermask to the Sn/Pb. It is especially true for larger features, ground planes, etc. If the board is then washed the condition can be aggravated by the chemistry and spray impingement resulting in additional loss mask or entrapment of wash residues. This was one of the drivers for going to a SMOBC style of construction, no melting metal under the mask. Regards Michael Barmuta Staff Engineer Fluke Corp. Everett WA 425-446-6076 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Lum Wee Mei Sent: Monday, May 07, 2007 5:37 PM To: [log in to unmask] Subject: Re: [TN] What is the difference between Fused SnPb and HASL? Thanks for the responds. From what I have gathered, fused SnPb can also have solder mask on them. My initial understanding or interpretation was that HASL finish is for SMOBC while fused SnPb finish is for board without solder mask. Regards, Wee Mei ________________________________ From: TechNet on behalf of Dehoyos, Ramon Sent: Mon 5/7/2007 10:15 PM To: [log in to unmask] Subject: Re: [TN] What is the difference between Fused SnPb and HASL? Wayne: Mostly copper with SnPb over it on some slivers. Pure copper from geometries such as traces and with SnPb such as pads. The slivers can be very small or very large. It depends on how it was removed. Large by hand and small by pumice spray. If they break off and wash away, no problem. If they partially break off and stay, they may shorten geometries. Other name for them is inclusions. Ramon >>>>> --------------- <<<<< The edges at the top will break off as slivers. | | | | | | | | ------- -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Wayne Thayer Sent: Monday, May 07, 2007 9:53 AM To: [log in to unmask] Subject: Re: [TN] What is the difference between Fused SnPb and HASL? Ramon- But it was the SnPb which had slivers, and if that is chemically etched away, then what are the slivers made from? Wayne >>> [log in to unmask] 5/7/2007 9:16 am >>> Wayne: That is affirmative. SnPb is removed from everywhere except the pads, lands and anything else that needs solder over the top of copper. At this time bare copper is oxidized and needs to be cleaned by hand or spray so that SMOBC can adhere to it and slivers brake off. Ramon -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Wayne Thayer Sent: Monday, May 07, 2007 8:56 AM To: [log in to unmask] Subject: Re: [TN] What is the difference between Fused SnPb and HASL? Ramon- What is it that needs mechanical removal? The oxidation of the copper traces due to selective SnPb removal? Wayne >>> [log in to unmask] 5/7/2007 8:46 am >>> Fused solder is more expensive and it takes about 5 more steps. When the SnPb is used as etch resist, as Wayne mentions, to pattern the outer layers and plate the pads and lands, the etching is not vertical so there is some underetching. slivers are formed at the top edge of the geometries. Later the traces have the SnPb taken off. So prior to having the solder mask applied, the copper traces are dull due to oxidation from etching the SnPb off which needs to be mechanically removed, leaving possible inclusions partially broken off. It can be a messy situation. Pads and lands are left with the solder over them which is later on fused by reflow oven. Thus the name fused solder. Most companies use HASL very few use Fused solder. Ramon -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Wayne Thayer Sent: Monday, May 07, 2007 8:14 AM To: [log in to unmask] Subject: Re: [TN] What is the difference between Fused SnPb and HASL? Werner is quite correct but only mentioned the metallurgy, not the ramifications for processing. HASL is a quite obnoxious process in terms of board stress during application, but most non-aggressive board constructs can handle it: The panel is plunged into a vat of molten solder and then withdrawn while being blown off with very hot air. The deposits are lumpy, and start giving problems for smaller parts. Fused SnPb is just convection heated to slightly above the melting point--no thermal shock. Also the deposits are extremely even, so very fine pitch work is no problem. However, the normal way of achieving Fused SnPb is to use the plated SnPb for the final etch resist. This means that if you have a board with a solder mask, then the SnPb will be under the mask, which will greatly reduce its effectiveness. Wayne Thayer >>> [log in to unmask] 5/6/2007 9:39 pm >>> Hello, I come across QML vendors that state their finish system : HASL, Fused Solder, while some only states : HASL. I know that HASL stands for "Hot Air Solder Leveling", what then is fused solder? There must be some difference between them - what are they? Thanks and regards, Wee Mei --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- This message (including any attachments) contains confidential and/or proprietary information intended only for the addressee. Any unauthorized disclosure, copying, distribution or reliance on the contents of this information is strictly prohibited and may constitute a violation of law. If you are not the intended recipient, please notify the sender immediately by responding to this e-mail, and delete the message from your system. If you have any questions about this e-mail please notify the sender immediately. --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------