Hi Leif,

One thing I noticed is in picture "test8" along the lead up towards the 
shoulder is the appearance of the plating. It sure looks like the plating I 
had on some AMP connectors at my last job:

http://stevezeva.homestead.com/files/Connector_Blumpies.jpg

Although yours doesn't seem as bad, but the same appearance is there. I just 
about bet that there is something going on with the plating on the parts 
that is giving you your problems, not your process...

Steve

----- Original Message ----- 
From: "Leif Erik Laerum" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, September 08, 2009 8:45 AM
Subject: [TN] Non Wetting Problem


> Technetters,
>
> We have a problem with non wetting on a very specific component. Only this 
> part exhibits the problem. These are double stacked FLASH TSOP components 
> that are stacked from the vendor.
>
> http://stevezeva.homestead.com/files/test6.jpg shows the same pin as in 
> test7 but enlarged.
>
> http://stevezeva.homestead.com/files/test7.jpg shows the most extreme case 
> with no heal fillet.
>
> http://stevezeva.homestead.com/files/test8.jpg hows another example with a 
> heal and toe fillet, but there is a crease on both sides of the pin
>
> The process is lead free. Our peak is about 245 for these components. We 
> hold peak for 20-30 sec. TAL is about 70.  I can not run much hotter since 
> there are large (676 pin) BGAs that reach 260. We have been all over the 
> spectrum with respect to profile. My revision log shows I have done about 
> 25 different ones. We have tried long soak, medium soak and short hot ramp 
> to spike. We have also experimented with different solder types. The 
> winner so far is a Water Soluble SAC305. The best results (least defects) 
> do come with a shorter RTS profile. The FLASH vendor recommends we peak 
> and hold at 255 -260 for ~30 sec. I am not able to do that since then the 
> 672 pin BGAs (3 of them) reach well above the recommended temp of 250. 
> With the current profile they are already at 260. As you have already 
> guessed, there is a 10 - 15 degree delta on this board that is very 
> heavily populated with these TSOPs. This board has in other words a large 
> mass. This condition does result in loose pins. It is not the same pins 
> every time either, so it does not appear to be related to the ground 
> planes. This is a 14 layer .062 board.
>
> The questions:
> 1. Any obvious remedies to eliminate the problem?
> 2  Anyone with similar experience?
> 3. How do you like my pictures?. I am trying out a new tool. This pics are 
> at 45X.
>
>
> -- 
> Leif Erik Laerum
>
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