Ditto on CTE mismatch & profile. 
Cu = 16.56 m/m*C
Au = 4.39 m/m*C
Ni = 12.96 m/m*C

Ni-Au = ??
 
 
 

> -----Original Message-----
> From: Mark E Witherite [mailto:[EMAIL PROTECTED]]
> Sent: Wednesday, April 03, 2002 13:56
> To: Protel EDA Forum
> Subject: Re: [PEDA] WANTED: PCB Expert (Off Topic)
> 
> 
> My Money is on the mismatch of thermal coefficient of 
> expansion between the 
> copper and the nickle gold foil.
> 
> At 04:52 PM 4/3/02 +0100, you wrote:
> >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
> > >
> 
> Mark Witherite  C.I.D.
> Assistant Research Engineer
> Astronomy & Astrophysics
> Penn State University
> 2565 Park Center Blvd
> Suite 200
> State College, PA.  16801
> email [EMAIL PROTECTED]
> telephone 814 865 9839
> fax           814 865 9100
> 
> 
> 

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