If the parts are so heavy and require shimm, what is the long term
reliability under such a weight?  Any study related to the creep or
vibration for these parts?
                                     jk
At 04:06 PM 5/1/00 +1000, you wrote:
>Rick is definitely a practitioner,
>
>shimming = set distanced, you can use teflon of validated thickness,
>hooked under corners .
>In practice it looks like a small spacer tack glued (something which burns
>off)under corners,
>you may opt for leaving/using/not/ middle one under;
>you can slice them of the common sheets/glide strips .
>Advantage to metal solutions (wire gauge) is taking minimal heat,planarity,
>and with a round (leather hole punch on brass plate on vertical press) shape
>even minimal jet deflection .
>Keep them tucked under - not to foul vision .
>Needle 'em out after pass.
>
>Watch for shadows on reflow air = don't get too close to balls .
>
>Rick may have a variation, 'd be interested to hear it myself .
>
>paul
>
>-----Original Message-----
>From: Stephen R. Gregory [mailto:[log in to unmask]]
>Sent: Saturday, 29 April 2000 5:44
>To: [log in to unmask]
>Subject: Re: [TN] I can't X-ray through this BGA!!!
>
>
>In a message dated 04/28/2000 1:17:19 PM Central Daylight Time,
>[log in to unmask] writes:
>
><< Steve,
>
> Just curious...is this the 35mm package with the big heat slug on the back?
> We place alot of the 'C6201 & 'C6701 parts. We had tried them with a
> Glenbrook unit and had the same results...very dark and barely able to make
> out the balls. In looking at x-ray units to purchase recently, I had
>several
> of the vendors x-ray these parts to see what the penetration was like. It
> seems that we needed 90-100Kv minimum to get a decent picture.  Glenbrook
> can't get there.
>
> On a related note, if you are placing the heavy heat-sinked part, did you
> have a problem with the balls collapsing too much under the weight?  That's
> a problem we've had since TI switched to this packaging.  We end up having
> to 'shim' the parts to get enough standoff distance. Just curious, as we're
> still searching for an efficient way to place and reflow these.
>
> Regards,
>
>
> Rick Thompson
> Ventura Electronics Assembly
> 2665A Park Center Dr.
> Simi Valley, CA 93065
>
> +1 (805) 584-9858 voice
> +1 (805) 584-1529 fax
> [log in to unmask] >>
>
>Hi Rick!
>
>We already had 5-boards loaded before we ran into the xray problem, so I
>went
>and reflowed them before I stopped the line. I want to make sure our
>customer
>knows the problem we have before I continue on...
>
>But I did reflow the 5-boards that we had already placed and did notice that
>the balls had collapsed a LOT more than I'm used to seeing...so in a word
>yes, I'm seeing the same thing that you see.
>
>Can I ask how you go about "shimming" these parts? Something that you do
>yourself, or something that you send the parts out and have done?
>
>Do you know if Texas Instruments is aware of the problem?...or is this one
>of
>the same kinda deals as palladium plating was with them.
>
>You know how that went; "There's nothing wrong with palladium plating...you
>just gotta find the right flux to use...simple!" ...and it may go the same
>way with this deal; "There's nothing wrong with this part, you just gotta
>find a way to shim it...simple!"
>
>Thanks for the heads-up Rick!!
>
>-Steve Gregory-
>
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