Bill,
Thanks for your response. I didn't state the actual issue very well. So I
shall start with that.
We observed two 0603 resistors cracked on several boards. The resistors are
placed near a swaged standoff, but not within the 0.75mm per IPC-2221 page
55. The line voltages and potentials per your response are not remarkable
enough to warrant a greater clearance. The standoffs in question are garden
variety Keystone 1589-2 #2-56 x 0.156 O.D. Keystone on its website
specifies a recommended staking tool, TL-19, which consists of a punch and
anvil. Keystone does not specify a particular tooling clearance or staking
force.
We may need to add a note on the assembly drawing about maximum swaging
force, in order to prevent the installer from damaging components due to
excessive force while swaging. But in my experience, the caveat when adding
such notes is, first you have to pay someone to set up the secondary op
step, then you have to pay someone else to inspect the first few articles,
then you have to pay for a jig, yada yada. All these costs get passed on to
the customer, whereby at the end of the day you may have created a cost
increase which could be overkill.
For next build I moved the resistors to the other side of the board, and
further away from the standoff area. That's fine, but I want to understand
the root cause for future edification. I would like to understand whether I
had to do this because I violated a rule of thumb, or whether I was
victimized by manufacturing ham-handedness, or a little of both, so I can
build the proper keepouts into the footprints for these swaged standoffs.
I don't know if some of the older specs such as IPC-CM-770 would give me the
rule of thumb that I need, or if I will need to email Keystone specifically.
Thanks,
Gary M. Koven, C.I.D.
Engineering Services Manager
Dynazign, Inc.
806 Tyvola Road, Suite 100
Charlotte, NC 28217
P: 704.405.1234 x210
F: 704.405.1402
http://www.dynazign.com/
better rendering of this issue.
-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of
Brooks,Bill
Sent: Monday, March 28, 2005 1:44 PM
To: [log in to unmask]
Subject: Re: [DC] Conductive pattern to mechanical hardware clearance
I don't believe there is a specific spec for what you are looking
for...someone please correct me if I am wrong...
The IPC-2221 page 55 has an example requirement that says for UNCOATED (no
soldermask or conformal coating) boards, you need .75mm minimum but not less
than allowed by the electrical clearance requirements...
The things that would govern the amount of spacing from any mounting
hardware would be voltage on the line in question relative to any voltage or
ground potential on the hardware, tooling clearance to swage or mount the
standoff, and installation tool (screwdriver?) and hardware clearance from
any screws and washers used in mounting the standoff to a chassis or
bracket. Also be concerned about clearance to any nearby component body as
well as the conductive pattern or any conductive non-insulated lead(s) from
the component involved.
If you are doing UL or TUV certification, there are more stringent
requirements to be concerned about... The ability to prevent shock hazard by
not allowing the end user to get their finger or a tool into an area that
will get them electrocuted across the line or from the line to ground,
spacing between the primary line voltages and SELV or Safety Extra Low
Voltage requirements at 48VDC or lower... secondary voltages... Distances
from Ground to the line voltages, line to line voltages, and on and on...
They are also concerned with Fire hazard... a failure shall not cause a fire
hazard... etc... It's a little more complicated...
Best regards,
Bill Brooks - KG6VVP
PCB Design Engineer , C.I.D.+, C.I.I.
Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510
e-mail:[log in to unmask]
http://www.dtwc.com
http://pcbwizards.com
-----Original Message-----
From: Gary M. Koven [mailto:[log in to unmask]]
Sent: Monday, March 28, 2005 10:11 AM
To: [log in to unmask]
Subject: [DC] Conductive pattern to mechanical hardware clearance
Which IPC specification will show the minimum clearance from conductive
pattern to mechanical hardware such as swage standoffs?
Right now I have approximately 0.025in (0.635mm) from via pad edge to
standoff lip edge, and want to make certain that distance will be
sufficiently robust for production.
The manufacturers' datasheets don't specify a recommended clearance, and
neither do the IPC-222X series specs.
Thanks,
======================
Gary M. Koven
Engineering Services Manager
Dynazign, Inc.
806 Tyvola Road, Suite 100
Charlotte, NC 28217
P: 704.405.1234 x210
F: 704.405.1402
http://www.dynazign.com/
----------------------------------------------------------------------------
-----
DesignerCouncil Mail List provided as a free service by IPC using LISTSERV
1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF DesignerCouncil.
To temporarily stop/(restart) delivery of DesignerCouncil send: SET
DesignerCouncil NOMAIL/(MAIL)
Search previous postings at: www.ipc.org > On-Line Resources & Databases >
E-mail Archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16
for additional information, or contact Keach Sasamori at [log in to unmask] or
847-615-7100 ext.2815
----------------------------------------------------------------------------
-----
----------------------------------------------------------------------------
-----
DesignerCouncil Mail List provided as a free service by IPC using LISTSERV
1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF DesignerCouncil.
To temporarily stop/(restart) delivery of DesignerCouncil send: SET
DesignerCouncil NOMAIL/(MAIL)
Search previous postings at: www.ipc.org > On-Line Resources & Databases >
E-mail Archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16
for additional information, or contact Keach Sasamori at [log in to unmask] or
847-615-7100 ext.2815
----------------------------------------------------------------------------
-----
---------------------------------------------------------------------------------
DesignerCouncil Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF DesignerCouncil.
To temporarily stop/(restart) delivery of DesignerCouncil send: SET DesignerCouncil NOMAIL/(MAIL)
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
---------------------------------------------------------------------------------
|
