Yap. Unless you used edge as both ground and thermal contact. However, for most of the PWA in Hi Rel usage, you have to use edge connector solder on PTH. No problem to coat without mask. If you got ZIF, you might as well use mask. You need on the ZIF any how (what ever the guard or Temp cover never work that well. My 1.98 cents.
--------------------------
Sent using BlackBerry
----- Original Message -----
From: Graham Naisbitt [mailto:[log in to unmask]]
Sent: Thursday, October 21, 2010 06:24 AM
To: [log in to unmask] <[log in to unmask]>
Subject: Re: [TN] Conformal Coating Board Edges
All
In my previous message I said that "in the past" this was done to reduce the risk of delamination. I know this did happen in service on many avionics assemblies when the research was conducted for NBC warfare effects.
I also know that most folks stipulated "no coating on the edges" to avoid having assemblies get stuck into their carrier frames.
I guess this was one of those classic problems encountered in the field that the designers had no clue about....until it was too late.
Given the role that a CC is intended to provide, wouldn't it be simpler, as was the case way before the advent of robotic systems, to permit edge coverage. Dip & Spray coating methods require masking that folks try to avoid, and as you can dip 600+ assemblies per hour in a dip process, its a popular application technique but a nightmare/dream if you have to mask.
In conclusion: IT DEPENDS! Ker-ching...
Regards
Graham Naisbitt - KBO
Email: [log in to unmask]
Phone: +44 (0)12 5252 1500
Web: www.gen3systems.com
On 20 Oct 2010, at 22:40, Douglas Pauls wrote:
> Thank you all for your responses. As indicated earlier, how I wish I
> would have had this kind of resource back in the 80s. Here are my
> thoughts on the matter.
>
> At Rockwell, home of truth justice and the American way, we do a great
> deal of coating by hand. A classic case of LEAN principles applied wrong,
> though I am told it made sense at the time. I am working on bringing back
> spray coating, but it is tough to change an entrenced culture.
>
> We have often required coating the board edges on our drawings, generally
> because "we have always done it that way". We may have done it for some
> of the reasons you all have given, but the technical rationale is probably
> buried somewhere in our archives. However, this edge coat requirement is
> selective in application. When the edges of the board have metal clad
> areas on top and bottom, such as with card guides, the edges are not
> coated, because it is very difficult to coat just the edge and not get any
> on the top or bottom card guide. Similarly, if we have a large high
> density connector on the board edge, that is flush mounted to the board,
> we do not coat the edge under that connector as it is next to impossible
> to do without flooding the connector surfaces. It is not unusual to have
> three out of four sides of an assembly uncoated (two card guides, one
> connector, one coated edge). So our apparent philosophy is to coat board
> edges unless it is too hard.
>
> One of the things that having a LEAN philosophy as a driver does for you
> is that you are constantly evaluating processes asking "is this really
> necessary?", or "is this value added?". For us, coating the edges of the
> board takes additional time and effort. It can also lead to rework or
> touch up activities as well. I cannot say we have ever had field failures
> or problems from board edges that are uncoated. Since we deal with some
> pretty harsh environments, if this had truly been a failure mechanism,
> such as for moisture ingress, we would have seen it by now.
>
> One of the key points for me, is that we are dealing with board edges that
> are routed, which has a tendency to seal the board edge, as opposed to
> punching or V-scoring, which can leave exposed fibers and has a greater
> risk of moisture intrusion. If I had punched or scored/snapped edges, I
> would consider edge coating to be necessary. But since I have routed
> edges, I ask myself the question of whether edge coating is value added.
>
> Would you agree with my reasoning?
>
> Inge, when you say board that are sensitive to water ingress, what do you
> mean? Is there a particular laminate material, such as Teflon or the high
> speed laminates, that is a consideration? Second, how do you determine
> how harsh an environment has to be in order to coat the edges?
>
> As for Parylene, remember, a nightmare is also a dream.............
>
> Now, to be perfectly honest, I can't really pass all this questioning off
> as high minded LEAN driven noble pondering. It's actually because I
> messed up last week. I used this reasoning on one, ONE mind you, program
> to relax the edge coat requirement for a tough application. Now I have a
> hundred requests, many along the lines of "Why do I have to coat my board
> edges if Donna does not have to coat hers, huh, huh?". There are some
> days here I REALLY don't want to be the coating expert.........
>
> Doug Pauls
>
>
>
> Inge <[log in to unmask]>
> Sent by: TechNet <[log in to unmask]>
> 10/20/2010 03:46 PM
> Please respond to
> Inge <[log in to unmask]>
>
>
> To
> [log in to unmask]
> cc
>
> Subject
> Re: [TN] Conformal Coating Board Edges
>
>
>
>
>
>
> Well, it depends..
>
> example 1: boards sensitive to water ingress via edges: we used
> multilayers
> of cc along edges
> example 2: boards with rough edges damaged the rack slides: we used cc
> along
> edges
> example 3: boards with smooth edges, no harsh environment: we did not use
> cc
> along edges
> there are more examples of course
>
> Conformal coating the edges was tricky, because of the sharp edges. The
> viscosity was therefore very important. Someone mentioned Parylene, that
> one
> has no such problem. Parylene is a dream stuff.
>
> Lately, we have skipped edge coating, except when the customer wants it.
>
>
> I had a look into MoonMan's POD, which covers most about PCB
> manufacturing.
> Strange enough, nothing about edge coating.
>
> Inge
>
> ----- Original Message -----
> From: "Douglas Pauls" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Wednesday, October 20, 2010 8:20 PM
> Subject: [TN] Conformal Coating Board Edges
>
>
>> Good afternoon all,
>>
>> I am glad we all appreciate Inge and the time he puts into making this a
>> fun and interesting forum. To sum up: Ditto.
>>
>> I have a question related to conformal coating, a sort of survey. For
>> those of you that conformally coat your assemblies, do you coat the
> edges
>> of the boards? Why or why not?
>>
>> There is an internal debate here and I wanted some other viewpoints
> before
>> offering my own.
>>
>> Doug Pauls
>> Rockwell Collins
>>
>> ______________________________________________________________________
>> This email has been scanned by the MessageLabs Email Security System.
>> For more information please contact helpdesk at x2960 or
> [log in to unmask]
>> ______________________________________________________________________
>>
>> ---------------------------------------------------
>> Technet Mail List provided as a service by IPC using LISTSERV 15.0
>> 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
>> -----------------------------------------------------
>
>
> ______________________________________________________________________
> This email has been scanned by the MessageLabs Email Security System.
> For more information please contact helpdesk at x2960 or [log in to unmask]
> ______________________________________________________________________
>
> ---------------------------------------------------
> Technet Mail List provided as a service by IPC using LISTSERV 15.0
> 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
> -----------------------------------------------------
>
>
>
> ______________________________________________________________________
> This email has been scanned by the MessageLabs Email Security System.
> For more information please contact helpdesk at x2960 or [log in to unmask]
> ______________________________________________________________________
>
> ---------------------------------------------------
> Technet Mail List provided as a service by IPC using LISTSERV 15.0
> 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
> -----------------------------------------------------
______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
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
-----------------------------------------------------
---------------------------------------------------------------------
This transmission (including any attachments) may contain confidential information, privileged material (including material protected by the solicitor-client or other applicable privileges), or constitute non-public information. Any use of this information by anyone other than the intended recipient is prohibited. If you have received this transmission in error, please immediately reply to the sender and delete this information from your system. Use, dissemination, distribution, or reproduction of this transmission by unintended recipients is not authorized and may be unlawful.
______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
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
-----------------------------------------------------
|
