Steve,

  My concern is related with board warpage inside reflow oven. Depending on
your panelization size and type ( v-score or tabs )you can induce more
warpage that can affect BGA to board contact. But you can put a wire inside
the oven ( front to end ) to avoid warpage in the same way that is used at
solder wave machine.

Thanks
Jorge Dourado de Santana
Maintenance / Process Engr
Microtec - Brazil



> -----Original Message-----
> From: Stephen R. Gregory [SMTP:[log in to unmask]]
> Sent: 19 de Janeiro de 2000 18:40
> To:   [log in to unmask]
> Subject:      [TN] [TN] Double-sided reflow with µBGA...
> 
> Hi-dee ho ya'll!
> 
> Gotta question, I gotta a lil' board here (.68" X 4.18") that is
> double-sided 
> (all SMT no through-hole) and has a 256-ball µBGA on one side. It's a 
> prototype right now (we're only building 5 or 10 assemblies). 
> 
> In my panelization recommendations I was thinking of having the panel made
> 
> with the boards alternating top/bottom/top/bottom etc., that way I would
> only 
> need one stencil, and we would only have to do one machine set-up when 
> building the panels, because we would be building both the top and bottom
> at 
> the same time. Once one side of the panel is built, you just take it from
> the 
> reflow oven and put it back into the printer to do the second side of the 
> panel, but you wouldn't have to change a thing on the printer or pick and 
> place machines because the bottom of the panel is an exact mirror of the 
> top...follow me?
> 
> Anyways, my real question is about double-sided reflow of the µBGA, I know
> 
> the surface tension will be there to hold the part, but I've never done it
> 
> before and don't know for sure if there will be any problems...I wouldn't 
> think so, but I though I'd ask ya'll to see if any of you have ever done
> it, 
> and if there were any problems.
> 
> Thanks ya'll!
> 
> -Steve Gregory-
> 
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