Victor,

To avoid a fourth call...

The upside down mounting (overcoat facing the PCB) of thick-film resistors or resistor arrays is not considered as a defect condition per IPC-A-610 (revisions E or F, but as a process indicator for IPC classes 2 & 3 applications.
I guess this would be treated as a defect if there was a known impact on functionality.

On this topic, you might be interested by the joint IBM-SK HYNIX paper of the last 2014 SMTAi conference entitled "Mitigation of Resistor Silver Sulfide Corrosion Through Design and SMT Process Optimization".
In this paper, the use of reverse R-nets was investigated as a way to mitigate the silver sulfide corrosion of resistor array terminations that commonly occurs under certain data center environments.
These reverse R-nets were introduced to improve the resistance to mechanical damages such as the ones resulting from mis-handling and hence reduce the propensity of terminal corrosion.
It was found to be a quite efficient mitigation practice using adequate design and assembly process rules.
The paper outlines that reverse resistors/R-nets came around 2010 and that they are now implemented in volume production for DIMMs.
Best regards,

A. Grivon

-----Message d'origine-----
De : TechNet [mailto:[log in to unmask]] De la part de Victor Hernandez
Envoyé : mardi 20 janvier 2015 15:08
À : [log in to unmask]
Objet : [TN] FW: Ceramic SMT resistor pack, RPac

Third Time is a charm!!!!!!

From: Hernandez, Victor G
Sent: Monday, January 19, 2015 2:51 PM
To: TechNet E-Mail Forum
Cc: Hernandez, Victor G
Subject: Ceramic resistor pack, RPac

Fellow TechNetters:

   I didn't get a response the first time, so I posted the second time.

Would the ceramic Rpac performance be compromised if installed with the carbon ink touching/facing toward the PWB solder mask surface.?   I have always seen these SMT facing up/away from the solder mask surface.

Victor,

From: Hernandez, Victor G
Sent: Monday, January 19, 2015 12:48 PM
To: TechNet E-Mail Forum
Cc: Hernandez, Victor G
Subject: Ceramic resistor pack, RPac

Fellow TechNetters:

   Would the ceramic Rpac performance be compromised if installed with the carbon ink touching/facing the PWB solder mask surface.?   I have always seen these SMT facing up/away from the solder mask surface.

Victor,


______________________________________________________________________
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] 
______________________________________________________________________