PCB Libraries Forum : SMD (Solder Mask Defined) and NSMD Pads https://www.PCBLibraries.com/forum/ Fri, 26 Jun 2026 20:47:05 +0000 Fri, 25 Sep 2015 05:20:00 +0000 http://blogs.law.harvard.edu/tech/rss Web Wiz Forums 12.07 360 https://www.PCBLibraries.com/forum/RSS_post_feed.asp?TID=1768 <![CDATA[PCB Libraries Forum]]> https://www.PCBLibraries.com/forum/forum_images/PCBLForumLogo.gif https://www.PCBLibraries.com/forum/ <![CDATA[SMD (Solder Mask Defined) and NSMD Pads : NSMD is normally used on every...]]> https://www.PCBLibraries.com/forum/smd-solder-mask-defined-and-nsmd-pads_topic1768_post7240.html#7240 Author: Tom H
Subject: 1768
Posted: 25 Sep 2015 at 5:20am

NSMD is normally used on every SMT pad due to registration tolerance of +/- 0.05 mm.
 
You do not want any solder mask on the pad so the minimum solder mask opening should be 0.05 mm.
 
The exception to this rule is Flexible Circuit libraries normally have a 0.05 mm solder mask over the Toe and Heel of the pad to act as an epoxy glue to hold the pad down while flexing the board.
 
]]> Fri, 25 Sep 2015 05:20:00 +0000 https://www.PCBLibraries.com/forum/smd-solder-mask-defined-and-nsmd-pads_topic1768_post7240.html#7240 <![CDATA[SMD (Solder Mask Defined) and NSMD Pads : So, which method will be better...]]> https://www.PCBLibraries.com/forum/smd-solder-mask-defined-and-nsmd-pads_topic1768_post7238.html#7238 Author: drj-bbe
Subject: 1768
Posted: 24 Sep 2015 at 10:26pm

So, which method will be better for PCB land pattern soldered BGA?

I have seen a describtion in IPC-7093 6.1.3.6 solder mask design. NSMD is better than SMD on QFN solder joint strenth. Should I assume that NSMD is first option for other chip, sop and connectors.
What about your opinion?
]]> Thu, 24 Sep 2015 22:26:22 +0000 https://www.PCBLibraries.com/forum/smd-solder-mask-defined-and-nsmd-pads_topic1768_post7238.html#7238 <![CDATA[SMD (Solder Mask Defined) and NSMD Pads : BGA pad size and solder joint...]]> https://www.PCBLibraries.com/forum/smd-solder-mask-defined-and-nsmd-pads_topic1768_post7237.html#7237 Author: Tom H
Subject: 1768
Posted: 24 Sep 2015 at 9:36pm

BGA pad size and solder joint relation is totally different than Chip, SOP and Connectors.
 
The NSMD BGA pad stack is necessary for the Ball to fully collapse around the pad edge securing it to the PCB -
 
 
The SMD (Solder Mask Defined) BGA pad stack prevents the Ball Collapse -
 
 
The BGA ball melts during reflow and other component leads do not.
 
]]> Thu, 24 Sep 2015 21:36:00 +0000 https://www.PCBLibraries.com/forum/smd-solder-mask-defined-and-nsmd-pads_topic1768_post7237.html#7237 <![CDATA[SMD (Solder Mask Defined) and NSMD Pads : Hi Tom: I know BGA land pattern...]]> https://www.PCBLibraries.com/forum/smd-solder-mask-defined-and-nsmd-pads_topic1768_post7236.html#7236 Author: drj-bbe
Subject: 1768
Posted: 24 Sep 2015 at 5:45pm

Hi Tom:
 
I know BGA land pattern design have two method, SMD(solder mask defined) and NSMD (non-solder-mask-defined), NSMD will be good than SMD for BGA pad to increase solder joint reliability.
 
What about other components? chip, sop, connector and etc.
 
Is NSMD also priority option for most components?
 
Is there any related description in IPC/JEDEC standard?
 
]]> Thu, 24 Sep 2015 17:45:09 +0000 https://www.PCBLibraries.com/forum/smd-solder-mask-defined-and-nsmd-pads_topic1768_post7236.html#7236