Phil,

Another reason could be US Patent 4,885,841 that was granted to my old boss
on December 12, 1989 for a "vibrational method of aligning the leads of
surface mount electronic components with the mounting pads of printed
circuit boards during the molten solder mounting process".  We even mounted
a hand held vibratin etching pen to our old Vitronics 722 oven to vibrate
the parts into place.  We were building singulated modules on a Quad Star
100 (mechanical part alignment, with no vision system).

Like you said, this was in many ways a band aid fix.  When we got our first
vision machine in, and started running paneled products in mid 1990, the
need for the vibration method went away, and all we had left was a plaque on
the wall.

Steve A

> -----Original Message-----
> From: Phil Zarrow [SMTP:[log in to unmask]]
> Sent: Tuesday,August 21,2001 12:17 PM
> To:   [log in to unmask]
> Subject:      Re: [TN] self-centering SMT
>
> Many years ago, there was a guy in New England selling a photo-optically
> triggered vibratory system for that very purpose.  The problem was, as
> John
> pointed out with his bearing problem, the vibration may or may not help
> self-alignment during reflow, but you don't want it (and this $25K system
> could not prevent)  vibration during cooldown.  Besides crappy looking
> joints
> there is a good chance of void formation.
> All of the oven people have known about the vibration-aiding-alignment
> scenario for years and, as competitive as reflow ovens were and still are,
>
> not one has ever offered it as an option.  Why? Because they know it is
> likely harmful.  Vibratory assist during repair is sometimes done since
> you
> can cease vibration during the cooldown portion of the profile cycle.
> Note
> that Conceptronic offered vibratory assist on their series of repair
> stations
> but not on their ovens.  They knew!
> Of course, there is the matter of principle - the oven should not be
> relied
> upon to compensate for the sins of the pick and place.  If a pick and
> place
> machine is properly programed, calibrated and maintained, it should be
> putting that component down properly.
> Leave the good vibrations to the Beach Boys!
> Regards,
> Phil Zarrow
> ITM Consulting
> Durham, NH  USA
> www.ITM-SMT.com
> Tel: 603-868-1754
> fax: 603-868-3623
> em: [log in to unmask]

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