I would second this point of Jack's The IPC has always said that those extra pads provide more stability, like a rivet with multiple "tabs" holding everything in place. And especially at the higher thermal stress on holes due to lead-free soldering temperatures, better to have the extra copper for reliability. We have had problems recently with this stability at hight temperatures.... Paul. ________________________________ From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of Jack Olson Sent: venerdì 25 aprile 2008 19.13 To: [log in to unmask] Subject: Re: [DC] Non-functional lands Well, that hasn't been my experience. It not that a manufacturer would ever require them or add them. The situation is, we supply a design in layers, and if you look at each layer individually you will see situations where a trace connects to a pad, and other situations where the pad is just sitting there with no connection to it. Maybe on a different layer there is a connection to that hole/via but not on the one you are looking at. There is no real reason you as a designer would remove these unused pads, but when you send this data to the vendor they see it as a easier process to take them out. Why waste drill bits drilling through copper that isn't even used? why take a chance that during lamination when everything goes "gooshy", that the pad will slide over and cause a short? Why not remove them? So, many times they don't ask and you would never know, they just delete your non-functional pads. end of story. except... The IPC has always said that those extra pads provide more stability, like a rivet with multiple "tabs" holding everything in place. And especially at the higher thermal stress on holes due to lead-free soldering temperatures, better to have the extra copper for reliability. In summary, its not that anyone adds non-functional pads. They are already there and the question is "can we remove them"? I say no. (but the IPC doesn't take a stand, for good reasons) hope that helps, Jack . On 4/25/08, Charles Gervasi <[log in to unmask]> wrote: This is probably a naïve question, but shouldn't the fab house know whether their process requires them and either add them using their CAM software or instruct you to put them in the design? ________________________________ From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of Jack Olson Sent: Friday, April 25, 2008 10:35 AM To: [log in to unmask] Subject: Re: [DC] Non-functional lands You won't find a spec that says non-functional lands shall not be removed. The IPC's postion is that if you think it is okay for the fabricator to remove them, they are not going to argue with you about it, but it has always been their position that they should be retained. but... If you decide that they can be removed with no detrimental effects, you still need to have them in the coupon so measurements can be made. If you want to retain them for hole reliability, you have to say it in a note (I think... Does anyone disagree with this?) There's plenty more discussion about why they should be removed or retained, but you didn't ask that, so I assume you know the issues and were just asking about the IPC specification onward thru the fog, Jack . On 4/25/08, James, Ron CAR <[log in to unmask]> wrote: Senile designer needs help. ;-) It has been a while since I have dealt with the question of removing or not removing non-functional pads from inner layers. I can't seem to find any record of what I told our board fabricators in the past. So I tried looking it up in the IPC specs. IPC-2222, 9.1.4 says that non-functional lands "should" be included on internal layers for all plated-through holes. It says "should" where many other paragraphs say "shall" in bold type; I assume that was done deliberately? Is this just a recommendation, and not a requirement? IPC-2221 only seems to mention non-functional lands in paragraph 12.4.1 describing test coupons, where it says that the coupon shall represent the design except that non-functional lands shall be included on all layers. The wording of this section suggests that non-functional lands would normally be missing, but they want them present on the test coupons. I can't find anything else, but I don't have a searchable PDF copy of the IPC specs, so there may be information that I am missing while flipping through my paper copy. A web search using the mighty Google shows multiple board suppliers who list removal of non-functional inner layer pads as a standard step in their CAM processing of customer Gerber files. I guess my question is: what IPC spec can I refer to to tell the fab house that they shall not remove unused inner layer pads? Or is it really OK? Ron ------------------------------------------------------------------------------- DesignerCouncil Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF DesignerCouncil To temporarily stop/(start) delivery of DesignerCouncil for vacation breaks send: SET DesignerCouncil NOMAIL/(MAIL) Search previous postings 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 ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- DesignerCouncil Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF DesignerCouncil To temporarily stop/(start) delivery of DesignerCouncil for vacation breaks send: SET DesignerCouncil NOMAIL/(MAIL) Search previous postings 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 ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- DesignerCouncil Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF DesignerCouncil To temporarily stop/(start) delivery of DesignerCouncil for vacation breaks send: SET DesignerCouncil NOMAIL/(MAIL) Search previous postings 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 ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- DesignerCouncil Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF DesignerCouncil To temporarily stop/(start) delivery of DesignerCouncil for vacation breaks send: SET DesignerCouncil NOMAIL/(MAIL) Search previous postings 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 ------------------------------------------------------------------------------- --------------------------------------------------------------------------------- DesignerCouncil 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 DesignerCouncil. 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