Hi Phil - as others have detailed, the use of a ORH1 flux means you have a highly active flux material. You can split the issue into two topics: (1) if you were just dealing with the flux being delivered to the solder joint in wire core form (no external flux additions), you would know that the flux was subjected to necessary soldering temperatures resulting in a flux residue. That flux residue must be removed by an appropriate wash process such that no residues are trapped under the gasket. If you can conduct testing to demonstrate that aspect, you would be good to go. However, as you described, the gasket makes the cleaning problematic. And as others have described, trapped ORH1 flux residue is not a good thing; (2) the use of an external liquid flux means you have the potential of having unreacted flux trapped under the gasket - a big issue that will result in corrosion in the product use environment. The use of an external liquid flux for this solder joint configuration should be prohibited with the use of a ORH1 material. The solder joint configuration with the gasket creates a huge material entrapment situation such that I don't think the use of external flux is appropriate. Dave Hillman Rockwell Collins [log in to unmask] Phil Bavaro <[log in to unmask]> Sent by: TechNet <[log in to unmask]> 10/10/2011 06:49 PM Please respond to TechNet E-Mail Forum <[log in to unmask]>; Please respond to [log in to unmask] To <[log in to unmask]> cc Subject [TN] ORH1 flux residues I have a PWA with a gasket beneath a large thru hole power device. The gasket has holes punched in it for each of the pins. The device is hand soldered flush to the PWB. The operator uses external liquid flux along with core solder with flux in it. The assembly is later washed and it passes ionics testing. The problem is that this gasket effectively seals the top side solder connections from the cleaning process. My question is this: How much should I be worrying about the existing hardware which has flux residues sealed under the power device? The assembly is stored with the power off. The flux used is water soluble and classified as ORH1. For future builds we are modifying the gasket so that the topside connections can be cleaned (cutout "u" shape intead of round holes). ------------------------------------------------------------------------------ This message and any attachments are solely for the use of the addressee and may contain L-3 proprietary information that may also be defined as USG export controlled technical data. If you are not the intended recipient, any disclosure, use or distribution of its content is prohibited. Please notify the sender by reply e-mail and immediately delete this message and any attachments. ______________________________________________________________________ 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 16.0 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 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 16.0 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 For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------