The Cyber-Spy.Com Usenet Archive Feeds Directly
From The Open And Publicly Available Newsgroup
This Group And Thousands Of Others Are Available
On Most IS NNTP News Servers On Port 119.
Cyber-Spy.Com Is NOT Responsible For Any Topic,
Opinions Or Content Posted To This Or Any Other
Newsgroup. This Web Archive Of The Newsgroup And
Posts Are For Informational Purposes Only.
Subject: Re: ESD immunity - large chassis / enclosure redesign question.
Date: Thu, 19 Sep 2002 13:12:49 +0800
X-Newsreader: Microsoft Outlook Express 5.00.2919.6600
Thankyou for your suggestions & comments guys
"Pat Carpenter" wrote in message
> If you have a serviceable unit then make sure that ESD procedures are
> carried out.
> 1 If possible have an anti-static floor, mat or other material on the
> floor in front of the unit (don't for get that wood is a good neutral
> material). Define it in the installation manual, also define the
> operating environment (I was caught out by a unit installed at the
> docks but they forgot to mention the large radar transmitter on the
> roof next door!)
> 2 Drill ESD wrist strap points (banana sockets) into the frame so that
> the service guy has some place to earth to. You could leave straps in
> place so that they are there already for use, but makes it hard to
> write the good QA procedure for strap integrity checking.
> 3 Enclose all the sensitive electronics in a metal box, use a hinged
> lid with copper/brylium seals. Use twist handles (increases pressure
> on seals) or at least spring twist screws (i.e not detachable so they
> won't get lost and don't forget that the more you use the less that
> will be re-done up).
> 4 An old favorite is if you have wheelable units, passing by, they
> often pick up very large static charges and if either bumped into the
> equipment or sometimes just pass very close-by they can transfer the
> 5 Maybe go the whole way and specify the torque settings on all
> fixings (these will be different depending on what metal is fix to
> what i.e steel/copper, alumimum/steel, etc)
> 6 Above all specify the manufacturing and servicing procedures
> exactly. If possible get hold of a video of ESD and its effects and
> show it to all your production and materials purchasing staff. It's
> very easy to allow a change to a part by the purchasing department
> without realizing its significance. If the equipment is large,
> expensive and has a service pack (containing special tools etc.) why
> not include a copy of the video with the pack?
> 7 Define all items and processes (i.e. connectors, cables, wiring
> layouts) which affect ESD performance and create a symbol to be placed
> on all diagrams, BOMs and purchase lists which defines that nothing
> can be changed to that part/process without sign-off from a named
> person or EMC designer. Also a good idea to have a symbol for safety
> components and processes, again requiring sign-off from the person
> responsible for safety design. It's too easy to buy a different part
> or just alter a layout without knowing why it was done that way!
> 8 As for the ESD fixing of the withdrawable unit, braids with copper
> tags (crimped and soldered) are better but be very careful of damage
> points, i.e. being un-done and then pinched or run over by the unit if
> it has wheels. Make sure all fixing points are marked and one of the
> servicing instructions is to visually and physically check the braids.
> Of course have a separate periodical test/inspection procedure.
> 9 The IEE (the British organization nor the IEEE) has an excellent
> manual on maintenance of equipment as opposed to a site
> infrastructure. Has good advice on periodic testing and risk analysis,
> for safety purposes, but can be adapted or added to for ESD.
> Hope some of the above is of some help, if you think I could be of
> further use please just email me any time.
> Pat Carpenter
> On 15 Sep 2002 22:19:35 +0900, Tom Sato wrote:
> >"Rob" writes:
> >> We are reworking a large product to make it more serviceable. We are
> >> remodeling the chassis (approximately 2m x 1m) so that a section (1m x
> >> will be able to be withdrawn for servicing etc. The structure is a
> >> frame with powder coated metal covers. During compliance testing we had
> >> quite a challenge to pass the ESD tests.
> >> I am trying to determine the best way to couple the removable section
> >> main chassis to optimise ESD immunity yet be easily and simply
> >> for the withdrawal. An important constraint is that the unit that is
> >> 'wheeled out' cannot be tightly (mechanically) coupled to the main
> >Although it would depends to some factors including structure of the
> >product (especially the structure around the removable section),
> >if finger strips can be used naturally, I suppose there is no reason
> >to reject the solution.
> >Bonding strap may not good for ESD when it can be long, and I think
> >it is not ideal for your situation anyway because it would be necessary
> >to remove the strap when removing the removable section.
> >Regardless of the bonding method, you may need to think of the route
> >of the possible ESD events, too, so that the ESD current would not
> >cause problem.
> >Tomonori Sato
> >URL: http://member.nifty.ne.jp/tsato/
Go Back To The Cyber-Spy.Com
Usenet Web Archive Index Of
The sci.electronics.design Newsgroup