IPC-7711A/7721A Rework, Repair and Modification of Electronic Assemblies has procedure 6.3 in the 7721A section that addresses a variety of component modifications. This particular concept has a common slang term of "dead bug" attachments, and is illustrated in procedure 6.3 Figure 12. The recommendation is to use insulation sleeving over the leads.
Please note that this document doesn't provide guidance on whether this method is appropriate or not for a given use, just a recommended approach.
Jack Crawford, IOM
IPC Director Certification and Assembly Technology
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dehoyos, Ramon
Sent: Friday, February 18, 2005 12:13 PM
To: [log in to unmask]
Subject: Re: [TN] Flipped transistor?
This seems to be a case for standardization. Is anyone from IPC or part vendor industry reading?
Ramon
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Cheryl Johnson
Sent: Friday, February 18, 2005 11:55 AM
To: [log in to unmask]
Subject: Re: [TN] Flipped transistor?
And let the one who ...
has NEVER had a SOT23 layed out wrong (with the 3 pins, every possible order is used by every different vendor - even among "same" part numbers...) ...cast the first stone...
Sincerely,
-----------------------------------
Cheryl Johnson, C.I.D.+
Manager
ExcelStor US Office, Engineering Services
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Tel: (303) 684-7291
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Mobile: (303) 809-5815
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Matthew Lamkin
Sent: Friday, February 18, 2005 9:32 AM
To: [log in to unmask]
Subject: Re: [TN] Flipped transistor?
It may not be what it was intended to be designed for, but once the component is soldered in what difference does it make?
Fair do's if it's going to be used on the next deep space probe or something really intensive, but for a general use board that is just going to sit there what harm can come of it?
Vibration will barely make any difference either way up.
So the component is upside down, but for an SOT23 the gap is not great when the legs are bent back.
Don't worry, life's full of too many hassles.
If it works, don't fix it.
Just out it down to being an Aussie part. ;-)
maybe best to raise an ECN though.lol
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Bissonnette, Jean-Francois
Sent: Friday, February 18, 2005 3:25 PM
To: [log in to unmask]
Subject: [TN] Flipped transistor?
Here is a first for me!
Before I go ruffling some feathers I would like to have others opinion.
I've just been informed of a modification on a boards that requires to install a SOT23 NPN transistor to be fliped on its back in order to be soldered. The poor leads are then bent backward to contact with the board's lands of some other component.
Engineering did not raise a flag on that yet... I'm worried to say the least because I'm convinced that this is a NO NO!
Anyone has seen that in the past?
Thanks!
Jean-François
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