If I understand this question right, then the undesirable reflow condition on the topside could be caused by the extra thickness of copper acting as an additional heat sink. The board would therefore need extra heat in order to solder. A way to design around this could be the use of thermal reliefs on holes that connect to the planes. This would limit the heatsinking properties of the internal power and ground planes. Another thing to look at would be the copper weight on the internal planes. Could these be reduced and still meet your design criteria? Finally, how much plane area is on the outer layers? These also tend to be heat sinks during soldering. ______________________________ Reply Separator _________________________________ Subject: ASSY: Topside Reflow on .062 boards Author: [log in to unmask] at SMTPLINK-HADCO Date: 5/6/96 10:43 PM Text item: Does anyone have any data on topside reflow on 4L boards? We are seeing reflow on .062 4L boards and the thought is that the I/L copper thickness is different for reflowed vs non reflowed boards. The boards that reflowed showed ~.002" copper while the non reflowed boards showed ~.0012" copper. The data is not statistically valid--too few samples. The construction is single ply 7628 for L1/L2 and L3/L4. Inner layers are planes. Text item: External Message Header The following mail header is for administrative use and may be ignored unless there are problems. ***IF THERE ARE PROBLEMS SAVE THESE HEADERS***. Resent-Sender: [log in to unmask] Precedence: list X-Loop: [log in to unmask] X-Mailing-List: <[log in to unmask]> archive/latest/3715 Resent-From: [log in to unmask] Resent-Message-ID: <"S6l4K2.0.HrL.6EEXn"@ipc> X-VMS-Mail-To: UUCP%"[log in to unmask]" To: [log in to unmask] Subject: RE: DES: copper thickness From: "Jeff Seeger" <[log in to unmask]> Message-Id: <[log in to unmask]> Date: Mon, 29 Apr 96 11:46:00 EDT Old-Return-Path: <simon.ipc.org!bort.mv.net!rapidcad!jseeger> Resent-Sender: [log in to unmask] Received: by ipc.org (Smail3.1.28.1 #2) id m0uDv6N-0000CPC; Mon, 29 Apr 96 10:43 CDT Resent-Date: Mon, 29 Apr 1996 11:42:44 -0700 Received: from ipc.org by simon.ipc.org via SMTP (940816.SGI.8.6.9/940406.SGI) id LAA05720; Mon, 29 Apr 1996 11:42:44 -0700 Received: from simon.ipc.org (IPC.ORG [168.113.24.64]) by ormail.intel.com (8.7. 4/8.7.3) with SMTP id JAA09967 for <[log in to unmask]>; Mon, 29 Ap r 1996 09:46:19 -0700 (PDT) Received: from ormail.intel.com by relay.hf.intel.com with smtp (Smail3.1.28.1 #2) id m0uDw5c-000qDTC; Mon, 29 Apr 96 09:46 PDT