Many thanks, Details are as follows:
6 Layer 1.6 FR4 8" x 10" Board PCB support is a wasted rectangle 10mm wide along all edges, supporting PCB at 2 or 3 points along each edge. (First observation is that this should have copper layers) Layer stack up is two cores + two foils (sizes rounded to 1 decimal place) R/P Layer Type thou - - Resist 0.4 R 1 Ni/Au 0.5oz 1.1 R 1 Foil 0.5oz 0.7 - - Prepreg 7630 7.0 P 2 1oz Copper 1.4 - - Core 15.0 R 3 1oz Copper 1.4 - - Prepreg 1080 5.0 - - Prepreg 1080 5.0 R 4 1oz Copper 1.4 - - Core 15.0 P 5 1oz Copper 1.4 - - Prepreg 7630 7.0 R 6 Foil 0.5oz 0.7 R 6 Ni/Au 0.5oz 1.1 - - Resist 0.4 --------------------------------- Total 64 = 1.625mm Effects are: Boards are flat from production, but twist on heating in solder reflow or wave solder. An analysis of 5 board produced 1 that exceeded the IPC warpage specifications. Trouble is all but one was too twisted to fit into the rack without effort. We had the same problem with the alpha version, but here this was put down to an incomplete plane on the two plance layers, this has been changed to a full plane - no change to warp. Suggestions so far have been to: 0: Add copper to waste (breakout) parts layers 1: Change the breakout to a waste part scored along the two long edges. 2: Use a three core construction 3: Add copper hash to layers 3 and 4, (other either side of the two cores) 4: Change warp and weft of cores 5: Increase core thickness and decrease 1080 prepreg thickness. 6: Use 1.8 FR4 by increasing core thickness (undesireable) So far we've had no input from the manufacturer as to what (if any) of the above will be better, though they agree that all should have some affect (positive or negative) on bow and twist. We've also noticed that over a long period (weeks) the twist gets less. Regards Jason. -----Original Message----- From: Mike Reagan [mailto:[EMAIL PROTECTED]] Sent: 03 April 2002 16:43 To: Protel EDA Forum Subject: Re: [PEDA] WANTED: PCB Expert (Off Topic) Jason Some of our advice is free What process is warping the boards? Reflow or manufacturing? or upset employee? Mike Reagan EDSI ----- Original Message ----- From: Jason Morgan <[EMAIL PROTECTED]> To: 'Protel EDA Forum' <[EMAIL PROTECTED]> Sent: Wednesday, April 03, 2002 9:03 AM Subject: [PEDA] WANTED: PCB Expert (Off Topic) > Hi, > > We have a board warping problem and are looking for a PCB expert to help > resolve it. > (Preferably located in the UK, but not important) > > When I say expert, I mean *EXPERT*. The problem is quite complex and already > has baffled two manufacturers. > > We will pay the going rate for any consultation. > > Regards, > > Jason Morgan > * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * To post a message: mailto:[EMAIL PROTECTED] * * To leave this list visit: * http://www.techservinc.com/protelusers/leave.html * * Contact the list manager: * mailto:[EMAIL PROTECTED] * * Forum Guidelines Rules: * http://www.techservinc.com/protelusers/forumrules.html * * Browse or Search previous postings: * http://www.mail-archive.com/proteledaforum@techservinc.com * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
