Hi, Ioan
It depends on which gel flux you are using and the methods used. Certain tacky fluxes (not solder pastes) such as Alpha WS609, WS1208, the halide-free WS619, and others change from a gel to a somewhat viscous liquid at about 90 degrees Fahrenheit, and then they can be blown under components or allowed to flow under components, and then reflowed. However, no flux should be allowed to flow into a cavity or other space where they are trapped and cannot be washed out. These gel fluxes cannot be dispensed in the needle bottle. I personally love the tacky fluxes for rework, because they stick around long enough to complete the job. They are especially useful for hot gas rework and hot wand rework.
Speaking of needle bottles, etc., make sure you do not allow your operators to put flux in small aluminum foil boats. Many fluxes react with the aluminum and when the flux is applied it will transfer the aluminum oxides to the part being soldered, and this will make for very poor solder joints.
I also cut off the needles on the bottles so they are only about .100" long. Too many times I have seen an operator accidentally bring his/her elbow down on the needle and actually inject flux into their skin from the pressure on the plastic bottle. A .100" length helps prevent the needle from breaking the skin surface, or at least from going deep. To make the cut use a simple lead cutter, apply only a small amount of pressure, and rotate the bottle so the needle is scored enough to snap it off cleanly. Trying to cut it off simply crimps it, rendering it useless.
As with any other flux, flux remover or material, you should qualify the application before using it in production. I have seen some "flux removers" that also removed the diallyl phthalate connector body as well!
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of John Goulet
Sent: Tuesday, December 07, 2010 12:47 PM
To: [log in to unmask]
Subject: Re: [TN] Gel vs liquid flux
The con would be that you can't get flux on the leads when they are under the connector orunder the body of a power module or relay.
A flux bottle with a small dispense needle is usually the best solution to get the flux where you need it on the component side.
A flux pen is used on the leads of a new part to be installed and on the PTh hole on the lead side.
Cleaning is required anytime you can't be sure all the flux wasn't heated to burn off the activators.
3M makes a great flux remover that works for WS flux and will remove the No-clean flux from under a component and not discolor any adjacent No-clean flux.
----- Original Message -----
From: "Ioan Tempea" <[log in to unmask]>
To: [log in to unmask]
Sent: Tuesday, December 7, 2010 10:01:33 AM
Subject: [TN] Gel vs liquid flux
Dear Technos,
What would be the cons against eliminating the use of liquid flux for rework and repairs and only using gel flux instead? I'm talking both WS and no-clean.
Thanks,
Ioan Tempea, ing.
Ingénieur Principal de Fabrication / Senior Manufacturing Engineer
T | 450.967.7100 ext.244
E | [log in to unmask] <mailto:[log in to unmask]>
W | www.digico.cc <http://www.digico.cc/>
N'imprimer que si nécessaire - Print only if you must
______________________________________________________________________
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 15.0
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
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 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 15.0
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
Please visit IPC web site http://www.ipc.org/ContentPage.aspx?Pageid=E-mail-Forums 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]
______________________________________________________________________
|
