TECHNET Archives

December 2013

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:
Joyce Koo <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Joyce Koo <[log in to unmask]>
Date:
Fri, 20 Dec 2013 16:44:02 +0000
Content-Type:
text/plain
Parts/Attachments:
text/plain (205 lines)
Design called shot (in your case is customer), because they have environmental, thermal constrain.  (I know exactly where is coming from... scary.  CM is not the one guarantee the reliability and life time of the products.. don't even mention the liability).  

Joyce Koo
Researcher
Materials Interconnect Lab
Office: (519) 888-7465 79945
BlackBerry: (226) 220-4760

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Reuven Rokah
Sent: Friday, December 20, 2013 11:18 AM
To: [log in to unmask]
Subject: Re: [TN] IPC-A-610E, Voids in Thermal exposed pad of QFNs

Hi All,
I started with this issue because of my customer needs (max 25% voids) and
argue with the EMS (one one the biggest) that its guide lines require 40%
maximum of voids.
In my opinion it should be included in the IPC-A-610 such as class 1, 2, 3
and above class 3 such as 10% voids (using vapor phase), should be agreed
between the two sides.


On Fri, Dec 20, 2013 at 3:04 PM, David D. Hillman <
[log in to unmask]> wrote:

> Hi Joyce - sometimes we can get too technical and over think a component.
> As you detailed, there can be a number of inputs to the equation but not
> necessarily. We have been using the 50% maximum void rule for 5 years on
> QFNs  and I have only 2 cases where we had either a thermal or grounding
> issue that required us to maintain a smaller voiding percentage of the
> thermal pad.
>
> Dave
>
>
>
> From:   Joyce Koo <[log in to unmask]>
> To:     'TechNet E-Mail Forum' <[log in to unmask]>,
> "[log in to unmask]" <[log in to unmask]>
> Date:   12/20/2013 06:45 AM
> Subject:        RE: [TN] IPC-A-610E, Voids in Thermal exposed pad of QFNs
>
>
>
> Correct me if I am wrong, as for the thermal goes, there are many factors
> just the voiding.  For example, the requirements of heat transfer path -
> vertical vs side, MCM possibly will have multiple grounds that may
> required isolation of heat path.  If you allow 50% voids, depend upon the
> thermal via path, you might missing one sector of the MCM heat conduction
> path all together (if it is vertically channeled).  It is not as easy as a
> single number.  It is a bit of scary when the design is so far above the
> supply chain.
>
> Joyce Koo
> Researcher
> Materials Interconnect Lab
> Office: (519) 888-7465 79945
> BlackBerry: (226) 220-4760
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman
> Sent: Friday, December 20, 2013 7:36 AM
> To: [log in to unmask]
> Subject: Re: [TN] IPC-A-610E, Voids in Thermal exposed pad of QFNs
>
> Hi Reuven - I think that is a possible idea, however, what void percentage
>
> do you suggest and what technical data/investigative studies do you have
> to support the recommended void percentage? One thing to consider is that
> if a workmanship topic is missing from the JSTD-001/IPC-610 documents, it
> doesn't mean that the topic hasn't been reviewed.  The IPC committees work
>
>  hard to only put workmanship criteria in the specifications that is
> necessary and is supported by data. An example - the IPC-7093 BTC
> committee completed extensive efforts looking at the voiding of QFN
> thermal pads and found no industry consensus on a void percentage
> requirement. The JSTD-001 committee therefore has not included a maximum
> void percentage requirement in the 001 specification and the IPC-610
> specification shows no examples of voiding requirements of QFN thermal
> pads. The workmanship criteria show in the JSTD-001/IPC-610 specifications
>
> results in added costs to products and processes so the committees are
> very careful to not add requirements unless there is technical
> data/justification. I know a number of OEMs/CEMS who have a 50% maximum
> void requirement on the QFN thermal pad unless the component has specific
> thermal or electrical functional requirements. The IPC-7093 specification
> has some good information on the topic of BTC thermal pads and voids. The
> committees would welcome any investigative data on the topic too.  Happy
> Holidays!
>
> Dave Hillman
> Rockwell Collins
> [log in to unmask]
>
>
>
> From:   Reuven Rokah <[log in to unmask]>
> To:     <[log in to unmask]>
> Date:   12/20/2013 12:48 AM
> Subject:        [TN] IPC-A-610E, Voids in Thermal exposed pad of QFNs
> Sent by:        TechNet <[log in to unmask]>
>
>
>
> Hi TechNets,
>
> I didn't see in the IPC-A-610E any acceptability reference in regards with
> the percentage of voids in solder joints of exposed thermal pads of QFNs
> or
> other components with exposed thermal pads.
>
> I recommend to add it in the next revision.
>
>
> --
>
> Best Regards,
>
> *Reuven Rokah*
>
> Mobile: 972-52-6012018
> Tel:        972-3-9360688
> Fax:          076-5100674
>  <http://www.rokah-technologies.com/>[log in to unmask]
> [log in to unmask]
> www.rokah-technologies.com
>
>
> This e-mail message is intended for the recipient only and contains
> information which is CONFIDENTIAL and which may be proprietary of
> RokahTechnologies. If you have received this transmission in error,
> please
> inform me by e-mail, phone or fax, and then please delete all of the
> original files and all other copies exist.
>
>
> ______________________________________________________________________
> This email has been scanned by the Symantec Email Security.cloud service.
> For more information please contact helpdesk at x2960 or [log in to unmask]
> ______________________________________________________________________
>
>
>
>
> ______________________________________________________________________
> This email has been scanned by the Symantec Email Security.cloud service.
> For more information please contact helpdesk at x2960 or [log in to unmask]
> ______________________________________________________________________
> ---------------------------------------------------------------------
> 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 Symantec Email Security.cloud service.
> For more information please contact helpdesk at x2960 or [log in to unmask]
> ______________________________________________________________________
>



-- 

Best Regards,

*Reuven Rokah*

Mobile: 972-52-6012018
Tel:        972-3-9360688
Fax:          076-5100674
 <http://www.rokah-technologies.com/>[log in to unmask]
[log in to unmask]
www.rokah-technologies.com


This e-mail message is intended for the recipient only and contains
information which is CONFIDENTIAL and which may be proprietary of Rokah
Technologies. If you have received this transmission in error, please
inform me by e-mail, phone or fax, and then please delete all of the
original files and all other copies exist.


______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________
---------------------------------------------------------------------
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 Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________

ATOM RSS1 RSS2