Alan Hilton wrote: Does this have any effect on hand-manufacturing? ie. Do you have to apply heat for a longer period in order to get a proper solder joint? Does it take appreciably longer to cool? At Rockwell, we do NOT put vias under smt pads. Because the stringers act as "thermal spokes", there are no soldering problems. ----- Begin Included Message ----- >From [log in to unmask] Wed Jun 26 09:36:55 1996 Resent-Date: Wed, 26 Jun 1996 11:34:54 -0700 Resent-Sender: [log in to unmask] Old-Return-Path: <[log in to unmask]> Date: Wed, 26 Jun 96 09:08:03 MDT From: [log in to unmask] (Gary Peterson) To: [log in to unmask] Subject: Re: DES:,FAB: - Thermal relief for via holes ?? Resent-Message-Id: <"AOxd93.0.Or6.f1Lqn"@ipc> Resent-From: [log in to unmask] X-Mailing-List: <[log in to unmask]> archive/latest/4865 X-Loop: [log in to unmask] Resent-Sender: [log in to unmask] Content-Length: 1946 We sometimes do the same (no thermals on SMT designs)...however there is always a price to pay. With buried planes, especially multiple planes for impedance control, lack of thermals make it necessary to preheat the board before hot-air removal/replacement of dead ICs. This is especially problematic when we have designed the board with vias-in-pads to cram too many parts on too small a board. The vias that connect directly to the planes take a lot of heat to reflow. Many a board has been burned by impatient individuals who turn up the temp on the hot-air tool instead of increasing the board pre-heat and increasing the hot-air tool airflow...and waiting 'till the solder flows on the power and gnd pins to lift the part. Gary P. --- Gary D. Peterson _/_/_/ _/ _/ _/ SANDIA NATIONAL LABORATORIES _/_/_/ _/ _/_/ _/ _/ P.O. Box 5800, M/S 0503 _/_/ _/_/_/ _/ _/ _/ _/ Albuquerque, NM 87185-0503 _/_/_/_/_/_/ _/ _/ _/_/ _/ Phone: (505)844-6980 _/ _/_/ _/ _/_/_/ _/ _/ _/_/_/_/ FAX: (505)844-2925 _/ _/_/ _/ E-Mail: [log in to unmask] _/_/_/ ----- Begin Included Message ----- HOWZITGOIN? Gary Willard wrote: ...are there any major concerns or advantages in having the vias connecting directly into the plane without relief... At Rockwell, flooded (no thermal relief) vias have been standard operating procedure for the last 5 years. We just photo plot a round circle that is smaller than the hole size (ie: .004") for each plane connection. It's small enough to get drilled away but large enough so the fab house doesn't think we forgot about those holes. Thank you and have a FANTASTIC day! Kevin L. Seaman (714) 221-4752 P.S. If your "reply" bounces back, then "send" to: [log in to unmask] ----- End Included Message ----- ----- End Included Message -----