Don’t see any problem. The weight per ball is 0.012gr.  
Assembled this components with no shorts. 
Critical to drill the PCB under the component for thermal probe position.
Pick temperature on the central balls 230-235C.
Stencil 4-5mil.
Pad (1mm pitch) 16 mil.

Sent from my iPad

> On 7 Jun 2018, at 2:20, Tan Geok Ang <[log in to unmask]> wrote:
> 
> Hi Steve,
> As you stated shimming is one of the methods and another way is to reduce the stencil opening dimension/ solder paste volume but this will lead to whether is it a cleaning or non cleaning process. If cleaning process, whether how effective it is.
> 
> GA Tan
> 
> 
> ________________________________
> 
> From: Steve Gregory <[log in to unmask]>
> Date: 7 June 2018 at 6:14:10 AM SGT
> To: [log in to unmask] <[log in to unmask]>
> Subject: [TN] High Ball Count BGA's with heavy heat spreader
> 
> Hi All,
> 
> I've been one of the lucky ones who hasn't had to deal with high ball count
> BGA's (1900+ balls) until now. I have a 1936-ball BGA that we are looking
> to assemble. I was able to get a couple of mechanical samples so that I
> could use them to dial my reflow profile in. When I got them, if I said I
> was surprised, that would be an understatement. This thing weighs close to
> an ounce with the heat spreader (23.133-grams):
> 
> http://stevezeva.homestead.com/1936_Ball_BGA_with_Heat_Spreader.jpg
> 
> So I remember reading threads on the Technet about shimming heavy, high
> ball count BGA's in the corners with something to keep the weight from
> squishing the balls out and causing shorts, I know that can happen because
> I have seen it on 1152-ball CBGA's from Xilinx.
> 
> Is there anybody willing to share some tips about assembling these beasts?
> At least I have a couple of mechanical samples I can play with before I
> dive in with live product....these are spendy.
> 
> Steve
> 
> --
> 
> 
> 
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