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August 2003

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Subject:
From:
"Dehoyos, Ramon" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Mon, 18 Aug 2003 10:37:31 -0700
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> -----Original Message-----
> From: Dehoyos, Ramon
> Sent: Monday, August 18, 2003 12:41 PM
> To:   [log in to unmask]
> Subject:      RE: [TN] placement verification of uBGA
>
>
>
>
>
>
>
>       Hal:
>               Do you know the component's body tolerances?
>               Regards,
>               Ramon
>
>
>       -----Original Message-----
>       From:   Hal Winslow [SMTP:[log in to unmask]]
>       Sent:   Monday, August 18, 2003 10:22 AM
>       To:     [log in to unmask]
>       Subject:        Re: [TN] placement verification of uBGA
>
>       Steve (and others...),
>       I would caution you about using a silkscreen pattern to align
> components.  Keep in mind that the silkscreen operation is only loosely
> aligned (probably +/- .005") to the circuitry patterns on the board, which
> is what you want your components aligned to.  This might be too much of a
> tolerance, especially if it is truly a uBGA you are placing.
>
>       Putting down the "chevrons" you mention would be the correct method,
> since they are perfectly aligned to the pads that your component is being
> placed on, since they are created during the same etching process.
>
>       Hal
>
>               -----Original Message-----
>               From: TechNet [mailto:[log in to unmask]]On Behalf Of
> Steve Gregory
>               Sent: Friday, August 15, 2003 5:56 PM
>               To: [log in to unmask]
>               Subject: Re: [TN] placement verification of uBGA
>
>
>               Hi Larry!
>
>               Something I've seen done before, is to either have a
> silkscreened outline of the part put on the board, or more recently with a
> board we built here, have "placement cheverons" etched into the board at
> the 4-corners of the device. Go to:
>
>               http://www.stevezeva.homestead.com
>
>               and look at "Placement Chevrons". Of course these have to
> match the outline of the body of the part, but the operators can easily
> tell visually, if the part is placed accurately or not....pretty slick if
> you ask me. But you do have a battle getting the designers to incorporate
> something like that.
>
>               -Steve Gregory-
>
>
>
>
>
>                       I'm wondering what you all use for placement
> verification of uBGA? Before running a new setup, we take a solder sample
> PCB and put double sided tape on it. Place the components on the PCB, when
> its finished the machine operator hauls the PCB over to the techs for them
> to Ersa and xray it to verify placement accuracy of the uBGA. I'm looking
> for something which would allow the machine operator to verify the
> placement themselves. Purchasing additional Ersa and xray equipment
> wouldn't be an option. Any suggestions?
>
>                       Larry
>
>
>
>
>
>               -Steve Gregory-
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