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August 1998

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Subject:
From:
"Devlin, Dan" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum." <[log in to unmask]>, "Devlin, Dan" <[log in to unmask]>
Date:
Fri, 14 Aug 1998 16:05:59 -0400
Content-Type:
text/plain
Parts/Attachments:
text/plain (140 lines)
Peter,
The chip components inside the DIP lead rows are not unusual.
The long axis of the DIP normal to the wave is not unusual. The
rationale for preference
of the short axis normal to the wave was driven by ease of insertion as
well as minimizing shorts
lead to lead.
Component orientation was not rigidly (comparative estimate) ten or more
years ago as it is now.
Good practice? Not by current standards. Problem in wave? Not with most
current generation wave solder
systems.
The chip components in arrays 2 virtually butted one to the other are
not a problem as long as they
have a common terminal between them.
The visual criteia may no show any sloping on the pad/chip joint but
this has been common practice in
dense RF circuits.
Hope the info helps.
:<)
Dan Devlin
> -----Original Message-----
> From: PETER [SMTP:[log in to unmask]]
> Sent: Friday, August 14, 1998 11:50 AM
> To:   [log in to unmask]
> Subject:      Re: [TN] DFM guidelines
>
> I was wondering if the smt resistors mounted between the DIP leads on
> the backside as shown below is a common and manufacturable design.
> I've
> not seen this before and since the boards are still in design, I can
> have my customer change this if necessary.
>
> Thanks,
> Peter
>
> <<snipped>>
> With this, they have positioned 6 1206's
> >> between
> >> the leads of a dip16 component and place 3 dip components in a row
> >> with 3
> >> 1206s between them.  ASCII art to follow.
> >>
> >> o - reps a dip lead
> >>
> >> [] - reps a 1206
> >> []
> >>
> >> <-----  conveyor direction
> >>
> >> o  []  []  o  []
> >> o  []  []  o  []
> >> o          o
> >> o  []  []  o  []    repeated 3 times in this direction
> >> o  []  []  o  []
> >> o          o
> >> o  []  []  o  []
> >> o  []  []  o  []
> >>
> >> Is anyone building anything like this successfully?  Volumes are
> less
> >> than
> >> 100/mo.
> >>
> >> Any input is appreciated.
> >>
> >> Peter Wong
> >> [log in to unmask]
> >>
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