TECHNET Archives

March 2005

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
Gene Felder <[log in to unmask]>
Reply To:
Date:
Wed, 23 Mar 2005 09:03:50 -0800
Content-Type:
text/plain
Parts/Attachments:
text/plain (325 lines)
Thanks Joe.

I was trying to find information of why the auditor failed the sister facility for not having ESD chairs.

It is clearly optional per ANSI/ESD S20.20, and thanks to your thorough reading also optional per EN 61340-5-1.

Hopefully Ron Gibson is right and the Europeans will adopt S20.20 before too long.

Gene Felder
[log in to unmask]

-----Original Message-----
From:   Kane, Joseph E (US SSA) [SMTP:[log in to unmask]]
Sent:   Wednesday, March 23, 2005 8:31 AM
To:     [log in to unmask]; TechNet E-Mail Forum
Subject:        RE: [TN] ESD Issue - non ESD Chairs on Manufacturing Floor

Last word on this subject.  I finally got a copy of EN 61340-5-1.
Paragraph 5.2.1 "General" says:

"Specific ESD protective items when used within an EPA (ESD protected
area) shall have the characteristics described in 5.2.2 to 5.2.11..."

Note the words "when used".  So this document does not require
use of conductive chairs, or clothing, or flooring.  This is borne out
elsewhere in the document, which says for example in Paragraph 5.5:

"The primary means of grounding personnel shall normally be by
a wrist strap connected to an EBP.  When the use of a wrist strap
system is impractical, the floor (see 5.2.3 and Table 1) and
footwear (see 5.2.8) shall be the primary means of ESD control.
When used, garments in accordance with 5.2.5 shall be worn and shall
be properly fastened at all times."

-Joe

-----Original Message-----
From: Gene Felder [mailto:[log in to unmask]]
Sent: Tuesday, March 22, 2005 12:00 PM
To: 'TechNet E-Mail Forum'; Kane, Joseph E (US SSA)
Subject: RE: [TN] ESD Issue - non ESD Chairs on Manufacturing Floor


I just review a Sanmina - SCI document from Northern California that
referenced IEC EN 61340-5-1.  This document was British Standard.  My
copy
has IEC 61340-5-1.  My understanding that it was adopted as the European

Norm so is now EN 61340-5-1.  The title of the document is
"Electrostatics,
Protection of electronic devices from electrostatic phenomena - General
requirements."  The "User Guide" is -2.

We go to market in Europe using our Charleswater brand and we use EN
61340-5-1.  It is very similar to ANSI/ESD S20.20.  I was surprised when
I
looked up yesterday and read the "shall be" regarding Seating.  I am
told
that SWAG 50% of users in Europe use ESD chairs.

Ron Gibson of Celestica and the ESD Association is the Canadian
representative to ISO; he has said that before too long Europe is likely
to
adopt S20.20.

 1.  Does the 61340 spec also require grounded floor? If not, each chair

would have to be grounded with a wire. Nasty, cumbersome, and a heck of
a
tripping hazard.
Yes, per EN 61340-5-1 section 5.2.3     Floors "All floor surfaces shall
have a
surface-to-EPA ground resistance in accordance with table 1." [same as
S20.20 < 1 x 10^9 ohms].

2.  Does the spec also require conductive clothing?  I don't see how
else
to make electrical contact between the person and the grounded chair.
Yes, per EN 61340-5-1 section 5.2.5 Garments "Coats, jackets, smocks and

overalls shall completely cover all clothing in the area of the arms and

torso. There shall be electrical continuity between all parts of the
garment. Garments shall have characteristics on the outward facing
surface
in accordance with table 1.  [Rp =/< 1 x 10^12 ohms vs. S20.20 1 X 10^5
to
1x10^11 ohms] Garments complying with ESD requirements shall be clearly
marked."
And is it mandated that such clothing cover one's seat when seated? I
find no mention regarding this

3.  I don't buy the argument that the chair should be grounded because
it
might be improperly used as a table.  By this logic, we should cover
every
horizontal surface in the shop.
If there is sufficient discipline on the shop floor, it would be costly
overkill.  ESD Association deals with this stating per ESD Protected
Workstations ESD-ADV53.1 Electrical Requirements, "Workstation elements
shall be connected to, and maintain electrical continuity to, the common

point ground as follows: Surfaces of shelves and drawers intended to be
used for unprotected ESD sensitive devices - Resistance: Between 1 x
10^6
ohms and 1 x 10^9 ohms."

4.  I don't think the reference to two grounded feet means the
operator's
feet.  I believe that conductive heel straps or footwear are designed to

meet grounding requirements with the person's full weight on them.  If
the
individual is seated, there is insufficient contact pressure with the
floor
to make a good ground path. That is my reading "When the floor is used
as
part of a grounding system, a minimum of two wheels or two feet shall
provide a path to EPA ground" is referring to the chair's feet. When
seated, the operator should wear a wrist strap. Right. Per EN 61340-5-2
section 5.2.4 "It should be emphasized that, where
operators are seated, a wrist strap approach should be used and seating
should form a secondary means of discharge.  S20.20 is even stronger
included in section 6.2.2.1. " When personnel are seated at ESD
protective
workstations, they shall be connected to the common point ground via a
wrist strap system."


Gene Felder
[log in to unmask]

-----Original Message-----
From:   Kane, Joseph E (US SSA) [SMTP:[log in to unmask]]
Sent:   Tuesday, March 22, 2005 6:08 AM
To:     [log in to unmask]
Subject:        Re: [TN] ESD Issue - non ESD Chairs on Manufacturing
Floor

We don't have grounded chairs either.

In my American parochialism, I'd never heard of the 61340 specs, and
none of our customers have ever mentioned them either.  Still, I'm going
to order some copies and have a look.

But I'm suspicious of such a "requirement".

1.  Does the 61340 spec also require grounded floor?
If not, each chair would have to be grounded with a wire. Nasty,
cumbersome, and a heck of a tripping hazard.

2.  Does the spec also require conductive clothing?  I
don't see how else to make electrical contact between the person and the
grounded chair.  And is it mandated that such clothing cover one's seat
when seated?

3.  I don't buy the argument that the chair should
be grounded because it might be improperly used as a table.
By this logic, we should cover every horizontal surface
in the shop.

4.  I don't think the reference to two grounded feet
means the operator's feet.  I believe that conductive
heel straps or footwear are designed to meet grounding requirements with
the person's full weight on them.  If the individual is seated, there is
insufficient contact pressure with the floor to make a good ground path.
When seated, the operator should wear a wrist strap.

Bottom line, if the person is grounded through a proper
wrist strap, it shouldn't matter what they are sitting on.

We might get an argument from someone who is selling chairs.

Joe Kane
BAE SYSTEMS Platform Solutions
Johnson City, NY


-----Original Message-----
From: Gene Felder [mailto:[log in to unmask]]
Sent: Monday, March 21, 2005 6:14 PM
To: [log in to unmask]
Subject: Re: [TN] ESD Issue - non ESD Chairs on Manufacturing Floor


Per ANSI/ESD S20.20 Paragraph 6.2.2.1  Personnel Grounding Requirement
"All personnel shall be bonded or electrically connected to ground or
contrived ground when handling ESD sensitive items.  When personnel are
seated at ESD protective workstations, they shall be connected to the
common point ground via a wrist strap system."

ESD protective Seating is an optional implementing process per Table 1of
ANSI/ESD S20.20; if used the minimum recommended technical requirement
range is < 1 x 10^9 ohms.

Included in the ESD Handbook TR20.20 section 5.3.5 is Static Protective
Seating "As mentioned in the floor materials section of this handbook,
the principle cause of static electricity in the workplace is cited as
the movement of people and materials. This routine movement,
particularly from a person seated in a chair or movement of the chair
itself across the floor, can generate significant voltages. This section
covers the use of seating in an ESD protected area for dissipation of
charge. Although not required in ANSI/ESD S20.20 as a primary means of
grounding personnel in the workplace, the use of chairs that meet
resistive requirements from the seat contact surface to the castors or
leg ends, may be an effective means of grounding personnel if a reliable
method can be found to bond personnel to the chair. In addition, if the
chair is used to connect personnel to ground than the maximum resistance
to ground from the person through the chair and flooring system should
be less than 35 megohms."

However, it is mandated per EN 61340-5-1. Per section 5.2.4 Seating "The
resistance from all areas of seating which may have human body contact
when in normal use, to either a floor contact point or a groundable
point, shall be as specified in table 1. [Rg =/< 1 x 10^10 ohms] When
the floor is used as part of a grounding system, a minimum of two wheels
or two feet shall provide a path to EPA ground."

Its EN 61340-5-2 User Guide states:
5.2.4 Seating
"It is important that low charging and grounded seating is used, as
although seating should never be used as a primary means of grounding
there are occasions where, through human error, equipment breakdown or
bad design it can provide an important resistive path to ground.
Although not recommended, in some EPA seats may be used as impromptu
working surfaces or storage surfaces. If nonconforming seating is used
then ESIDS may be damaged in this way. Where grounded, if footwear is
used rather than wrist straps, when seated, many operators will spend
periods when footwear is not in contact with the ground. Charges and
potential can build up where there is no path to ground. In this case, a
path may be provided through the garments (see 5.2.5), provided they are
in contact with the seating. It should be emphasized that, where
operators are seated, a wrist strap approach should be used and seating
should form a secondary means of discharge. In the event that an ESID
coordinator should decide that there is no suitable alternative to using
seating as the primary grounding approach, resistance to ground should
comply with the same requirements as wrist strap systems, or for
flooring and footwear (i.e. 750 kQ to 35 MQ) (see 5.2.8). Seats in
compliance with IEC 61340-5-1 should carry suitable labels (see clause
4) to help with identification. It is permissible for those parts of
seats which are unlikely to come into contact with the body or with
ESIDS, for example the underside of the seat, to be made of
non-compliant materials."

Gene Felder
[log in to unmask]

-----Original Message-----
From:   Dale Ritzen [SMTP:[log in to unmask]]
Sent:   Monday, March 21, 2005 2:53 PM
To:     [log in to unmask]
Subject:        [TN] ESD Issue - non ESD Chairs on Manufacturing Floor

A sister company of ours has just undergone an ESD audit by one of their
customers. During the audit, they were cited for allowing non ESD chairs
(i.e. no drag chains and/or conductive wheels/legs) in the manufacturing
areas. I looked in IPC-A-610, in section 3.2 (ESD/EOS Safe Workstation)
and find no reference to non-ESD chair use. Simply put, if a solder
operator, assembler, etc. is seated in a non ESD chair, but wearing heel
straps (on a dissipative floor) and is jumpered to a grounded jack via a
wrist strap my take is that they are sufficiently grounded to perform
their work. I have never had any external ESD audit fail for this
reason.

Anyone else have any experience with this type of call? I don't have a
copy of ESD S2020 so I can't refer to it for help in this case. Thanks!

Dale Ritzen, CQA
Quality Manager
Austin Manufacturing Services

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e To
unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or
(re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at:
http://listserv.ipc.org/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
-----------------------------------------------------

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e To
unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or
(re-start) delivery of Technet send e-mail to [log in to unmask]: SET
Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the
posts: send e-mail to [log in to unmask]: SET Technet Digest Search the
archives of previous posts at: http://listserv.ipc.org/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
-----------------------------------------------------

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e To
unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or
(re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at:
http://listserv.ipc.org/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
-----------------------------------------------------

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/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
-----------------------------------------------------

ATOM RSS1 RSS2