in 99SE anyone know how to get the DRC in PCB for unconnected pads to work? (on the 'Other' tab)
first observation
it says it detects 'pads w/ no tracks' but it seems that if you load a netlist using 'include single pin nets' that those pads will not be flagged due to the presence of a net label (i guess), but that's ok by me
so given that if i load a netlist with 'include single pin nets' unchecked and then
if i make a pad class with all the pads i know are ok to be N.C. then add a rule for that class in addition to 'whole board' then
all the unconnected pads in the class are grouped into one section of the DRC report and all the rest are in another section of the DRC report, but
ALL of the given pads from both rules light up DRC green, which makes it almost useless to me
i want to just light up pads that i have not specified as ok to be N.C.
TIA
Dennis Saputelli
_______________________________________________________________________ Integrated Controls, Inc. Tel: 415-647-0480 EXT 107 2851 21st Street Fax: 415-647-3003 San Francisco, CA 94110 www.integratedcontrolsinc.com
Harry Selfridge wrote:
Hi Darcy,
The following is strictly my opinion from an engineering standpoint.
There are too many variables to define "excessive" flexure. Deflection of a PCB in one direction may cause no problem, but may crack a SMD capacitor if it happens 90deg offset. Likewise, flexure across a pcb trace may cause no harm while flexure in line with the trace might crack the trace. Amount, direction, rate of flexure, number of deflections, board composition, board stackup, copper weight, surface plating, temperature, component sizes, size and location of board mounts, etc, all would affect the end result of flexure.
There are some tried-and-true methods for stiffening a board in areas of concern. A vertical metal rib can be soldered to the top or bottom of the board. Mounts can be placed under the point of pressure (screwed or glued plastic or hard rubber bumpers) to limit travel. Sockets/connectors can be mounted to the enclosure to transmit insertion force to the enclosure rather than the board. Stiffening support frames of plastic of metal can be mounted to the enclosure. Etc.
Flex mounting the board can be done in a number of ways. There are press-fit nylon board standoffs, and flexible screw type nylon standoffs. Belleville, or wave spring washers can be used under the board at the mounting points. Mounting holes can be inserted with rubber or plastic grommets. Mounting screws can be bottomed in mounting standoffs, leaving "drift" clearance. Etc.
The "right" solution for your problem is going to be unique to your application. It may be one, or a combination, of some of the kinds of things I mentioned above.
Regards - Harry
At 07:50 AM 4/14/05, you wrote:
Hey Guys,
One of the latest issues we've run across (while trying to balance weight,
size, money) in a current design is that there is some potential for
mechanical stresses to be induced into the PCBs in the end user product.
This causes a couple issues. The first is the obvious solder joint integrity
and the possibility of damaging components or traces on each PCB. The
second is the alignment of a board to board connector (Hirose DF12 series)
between two PCBs. My first gut reaction is "absolutely no stresses are
acceptable in the PCB," but since we're balancing the above objectives, I
thought I'd throw some questions out.
1) Has anybody got an opinion or has read some article on allowable stress
or flexure of populated PCBs?
2) Have you seen any sort of flexible mount that could be used to "float" the PCBs. Currently we're using 3mm screws to secure the PCBs so we're looking for a solution that would be the same order of magnitude in size (ie. Chev 454 motor mounts are too big!)
Thanks for any suggestions you may have.
Darcy Davis Design Engineer, Dynastream Innovations, Inc.
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