Assembly house is not a reliability expert. Vias that closed on one side have long term reliability issues.
Veronika Anderson C.I.D | Sr. Electrical/Mechanical Design Engineer | Excelitas Technologies
Office: +1 626.967.9521 x 236
1330 East Cypress Street, Covina, CA 91724 USA
[log in to unmask]
www.excelitas.com
-----Original Message-----
From: Greg Smith [mailto:[log in to unmask]]
Sent: Thursday, April 24, 2014 8:18 PM
To: (Designers Council Forum); Anderson, Veronika
Subject: Re: [DC] IC's with a "ground slug" with vias...
I certainly agree that the best options are to plate the vias closed or fill them with either electrically or thermally conductive material and plate over.
However this can put the PCB cost over budget and therefore is not applicable to some projects. The project I cited was a "box build" done off shore. Cost was everything (not my choice). On the other hand I had to recognize that the assembly house built more different PCB designs in a week than I worked on in several years. So if they said a method would work it was hard to argue with out solid proof. I was always disappointed I did not get a chance to really investigate the solder joints we were getting on that job.
On 4/24/2014 2:54 PM, Anderson, Veronika wrote:
> Vias shall be either closed or opened from both sides.
> Opened via will lead to a solder joint starvation and requires a manual post reflow operation to fill vias with solder from secondary side. This will eliminate the solder peaks as well.
> This is suitable for low volume production only.
> In mass production you better use via-in-pad technology - vias shall be filled with nonconductive epoxy, planaraized, and plated with copper over the filled via.
> The best option is - to have via plated though with solid copper.
> However, this technology available from Via System (former DDi /
> Anaheim, CA) only
>
> Veronika Anderson C.I.D | Sr. Electrical/Mechanical Design Engineer |
> Excelitas Technologies
>
> Office: +1 626.967.9521 x 236
> 1330 East Cypress Street, Covina, CA 91724 USA
> [log in to unmask] www.excelitas.com
>
> -----Original Message-----
> From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of
> Greg Smith
> Sent: Thursday, April 24, 2014 2:34 PM
> To: [log in to unmask]
> Subject: Re: [DC] IC's with a "ground slug" with vias...
>
> I went through this a few years ago. We had a pcb with voltage control
> ICs that used the center slug as a ground and heat sink. These were
> quad no lead parts. I originally left the vias open with a "partial
> tent" on the back side: the mask left a small annular ring of exposed
> plating around the hole, with no mask on the component side. Solder
> flowed into the holes and left a small bump on the back side. It
> seemed to work fine. However, in production, our off-shore assembly
> house requested a change. They felt the vias were starving the pad of
> solder on the component side and, for some reason, did not like the
> look of the solder protruding on the far side. They requested that the
> vias be "capped" on the far side. The cap is a second application of a
> more viscous mask that will close the hole opening. It requires
> another CAD artwork layer to define it. After much debate, fearing
> trapped air would "volcano" at worst, or create solder voids under the
> slug, we agreed to do it. The assembly shop did a test run with no
> issues on their side. As far as I know it worked but since this was a
> production run, in limited quantities, with customer demand, I was not
> able to get a sample to
> (destructively) test. We were not driving the ICs very hard so I don't know how thermal performance was affected.
> As this type of chip was becoming more popular I found a real lack of support by the manufacturers. There were fairly nebulous instructions for footprints and a lot of different ideas on what worked. In fact, at one time, Texas Instruments had out two white papers on the subject that came to exactly opposite conclusions. I don't if that has changed any in the last 2 years.
>
>
> On 4/24/2014 1:25 PM, Jack Olson wrote:
>> If you tent the back side you will have a risk of little volcanoes
>> underneath the part during soldering.
>>
>> The document you are thinking of is IPC-4671 (Design Guide for
>> Protection of Printed Board Via Structures)
>>
>>
>> On Thu, Apr 24, 2014 at 2:58 PM, Fred Dark <[log in to unmask]> wrote:
>>
>>> Hello all - we have been adding a solder-mask dot on the same side
>>> as the IC's with a "GND-SLUG"... no issue... however if a "SLUG" has
>>> a large quantity of vias due to the requirement to dissipate heat
>>> here is where I have a issue... not enough area for paste and proper
>>> solder percentage to the area... so in this case I was suggesting to
>>> tent the opposite side that the IC resides on... filling, capping
>>> and planarized is the way to go, however would tenting the opposite
>>> side be a issue..? note via hole size is 10mils... anyone aware of the IPC standard and or requirement..?
>>>
>>> Regard's, Frederick Dark Jr.
>>> Manager Senior PCB Designer
>>> Crestron Electronics, Inc.
>>> 22 Link Drive Rockleigh N.J. 07647
>>> P:201.750.7004 ext.11320
>>> F:210.767.5772
>>> [log in to unmask]
>>>
>>>
>>>
>>> This e-mail message and all attachments transmitted with it may
>>> contain legally privileged and confidential information intended
>>> solely for the use of the addressee. If you are not the intended
>>> recipient, you are hereby notified that any reading, dissemination,
>>> distribution, copying, or other use of this message or its attachments is strictly prohibited.
>>>
>>> ____________________________________________________________________
>>> _ _ 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]
>>> ____________________________________________________________________
>>> _
>>> _
>>>
>>>
>>>
>>> --------------------------------------------------------------------
>>> -
>>> ------------ DesignerCouncil Mail List provided as a free service by
>>> IPC using LISTSERV 16.0.
>>> 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) For additional information, or contact
>>> Keach Sasamori at [log in to unmask] 847-615-7100
>>> ext.2815
>>>
>>> --------------------------------------------------------------------
>>> -
>>> ------------
>>>
>> _____________________________________________________________________
>> _ 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]
>> _____________________________________________________________________
>> _
>>
>> ---------------------------------------------------------------------
>> -
>> ----------- DesignerCouncil Mail List provided as a free service by
>> IPC using LISTSERV 16.0.
>> 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) 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 Symantec Email Security.cloud service.
> For more information please contact helpdesk at x2960 or
> [log in to unmask]
> ______________________________________________________________________
>
> ----------------------------------------------------------------------
> ----------- DesignerCouncil Mail List provided as a free service by
> IPC using LISTSERV 16.0.
> 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) 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 Symantec Email Security.cloud service.
> For more information please contact helpdesk at x2960 or
> [log in to unmask]
> ______________________________________________________________________
>
>
> ----------------------------------------------------------------------
> ----------- DesignerCouncil Mail List provided as a free service by
> IPC using LISTSERV 16.0.
> 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) 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 Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
---------------------------------------------------------------------------------
DesignerCouncil Mail List provided as a free service by IPC using LISTSERV 16.0.
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)
For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
---------------------------------------------------------------------------------
|
