I have had customers like this too. These are the same guys who will bring up the theory of "acid traps" and are so scared of "exposed copper" (really just areas which aren't covered with mask which you don't intend to solder to) that they won't use it even if it improves yield. All of these are part of "good design folklore".
True, if metal under components can be avoided at no cost then that is preferable for rework/board mod/test issues. But the improvement is extremely marginal unless the board is poorly designed and manufactured. If a solder bridge does happen in an area which is not visually inspectable, then it is more expensive to diagnose. But first we have to have bad mask design and/or placement, and then we have to have stray solder get under the part.
These same customers go berserk when you suggest using a single wire jumper to eliminate two layers of board and blind vias. "How dare you start implementing 'white wires' before the first run is even made to work!".
Customer is "KING". We make like they tell us. It is our job as designers to tell them the consequences of what we perceive as micro-management (as long as we don't tick them off when we tell them!).
Wayne Thayer
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Upton, Shawn
Sent: Wednesday, March 18, 2009 11:59 AM
To: [log in to unmask]
Subject: Re: [TN] Traces and vias under components
Rework issues? Hard to cut a trace under a component. Also, are they using tented vias? Untented via's are easy to probe, while tented ones are bit harder.
Shawn Upton, KB1CKT
Test Engineer
Allegro MicroSystems, Inc
[log in to unmask]
603.626.2429/fax: 603.641.5336
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Kevin Glidden
Sent: Wednesday, March 18, 2009 11:54 AM
To: [log in to unmask]
Subject: Re: [TN] Traces and vias under components
If it's a space issue, that's your argument.....if not, why argue?
Customer is always right........
-----Original Message-----
From: wheels [mailto:[log in to unmask]]
Sent: Wednesday, March 18, 2009 11:01 AM
To: [log in to unmask]
Subject: [TN] Traces and vias under components
Guys,
We have a customer which we are designing a mostly SMT board for that requires all traces and vias not to be under components. This would also include any planes being under the components. I guess in the past they had a board designed by some else that had a shorting problem with traced and vias under the components. They are insistence that this is the way it has to be. Has anyone else had experience with this sort of demands? This is not for space, military, high voltage, high vibration or a medical application.
Can anyone think of anything we could tell they to change their mind?
Thank you,
wheels
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