Hello TechNetter!
Question for all the wave solder folks. Have any of you found a way to totally eliminate dross from your wave solder machines?

Set the solder pot temperature knob to "off". But seriously, you can greatly reduce dross formation by inerting with nitrogen, but I don't know of any methods to totally eliminate dross.

Greg Kilinski
Acuson Corp.
HYPERLINK mailto:gkilinsk@acuson.com gkilinsk@acuson.com

To: MAIL@CSERVE {INTERNET:TECHNET@IPC.ORG}
From: MAIL@CSERVE {INTERNET:TechNet@ipc.org}
Subject: assy: Dross elimination
Date: 14-Aug-96 18:19

Eliminate.......No!
Drastically reduce yes!

We have two insert atmosphere(Nitrogen) wavesoldering systems. As well as the greatly improved quality of soldering, they produce almost no dross in comparison to conventional systems.We NEVER experience solder defects cause by dross being circulated in the wave, which did happen on our previous equipment even though we maintained the pot and pump well.

Regards

You can "poison" you solder pot with phosphorous. The deoxidation property of phosphorous will slow the formation of dross. However, excessive quantity of phosphorous will affact the wetting properties of the solder.

M. Yuen

Are you sure you really want to eliminate dross? Years ago I ran an oil covered solder bath that developed very little dross. On the other hand contaminants (copper and gold) built up and the pot would have to be dumped completely. It was a job shop so quantity and type of PWA soldered varied. This led to frequent sampling and testing for contaminants so it wouldn't get out of hand. Economic analysis led us to believe that a "dry" (no-oil) wave was less expensive overall since the dross carried the contaminants out with it.

We also tried a powder chemical that put the dross back into solution, but it created the same problems as the oil.

Gordy Seppanen
Materials Engineer-Surface Finishing Lab
Honeywell Inc
612/951-5522
HYPERLINK mailto:seppanen_gordy@mn15-gw.mavd.honeywell.com seppanen_gordy@mn15-gw.mavd.honeywell.com

Long, Gregory (Gregory.Long@IAC.honeywell.com)
13 Feb 1997 16:21:11 -0600

Does anyone out there in Flow Solder land use Kleenox dross reducing agent and if so do you see any abnormal material on the sides of walls in the solder pot or built up on the splash plates of the chip and lambda waves.

gregory.....

The material does what it says it does. You must mix it in to the dross layer then wait. Then remove the dross by squeezing it through a ladle to separate the solder from the oxides. I have been running the Workshop of Machine Soldering for over ten years for one of the most well known flow solder machine manufacturers. The same course that is run in Dallas in the USA. All the service engineers in the UK think its a great material and it works for them. I think it stinks and I just cant stand the smell so I never use it.

If you just sprinkle the material on and leave it the residues will build up. You still have to remove the dross in the normal way it just aids separation.

Bob Willis
Process Engineering Consultant
Electronic Presentation Services
2 Fourth Avenue, Chelmsford, Essex CM1 4HA. England.
Tel: (44) 01245 351502
Fax: (44) 01245 496123
Home Page: http://ourworld.compuserve.com/homepages/Bwillis
Email: HYPERLINK mailto:100537.2615@compuserve.com 100537.2615@compuserve.com

Hi Greg -

We have used the Kleenox material off and on depending on the process situation. We have never had an issue with it except for the really wonderful odor that is generated as it does its job. It doesn't take very much Kleenox to de-dross the pot - are you using too much thus ending up with buildup or maybe you are having a Kleenox/flux reaction.

Dave Hillman
Rockwell Collins
HYPERLINK mailto:ddhillma@cacd.rockwell.com ddhillma@cacd.rockwell.com

We are using ELECTROVERT 08 Hot Air Solder Levelling Machine for the last 8 years. It has a solder bath of 500 kgs.

We have been regularly using KLEENOX for dross control and monitoring the solder for trace impurities being built up during the use. As soon as Cu contamination touches 0.3% mark we change the solder. This change becomes due after an average throughput of 1500 sq mtrs .

On comparing notes with other PCB shops in India and Europe we realise that very few people resort to changing of the whole bath. Most of them keep removing 40-80 kgs from time to time and keep replacing it with virgin chip solder. Another practice being resorted to by many is raising of molten solder temperature to 300 Degrees Centigrade (572 F) keeping it at that for a while then skimmimg out the top layer and replenishing it to the desired level by virgin solder. This system the practitioner's claim brings the Cu to the top and thereby controls contamination more effectively.

I would be very glad to hear from the Tech netters on the best industry practice in this regard.

Anil K Singh
Linaks Microelectronics Limited
Fax:+91-522-222061, 315978

I have not heard of raising the temperature of the solder. We lower the temperature to just above Eutectic 180C (356F) overnight and remove the crystalline dross which accumulates in the morning. We do this every day and have not had to change the solder for some time. This procedure holds copper between 0.2 and 0.25% maximum.

There should be sufficient turnover of the solder bath to keep the copper level low provided you are not dragging in excessive amounts. Look critically at the pre-clean process to make sure you are not dragging copper contamination into your flux.

I would also question the use of Kleenox in this application. We use a similar product on our flow solder machines but I would rather throw out more dross and the copper with it on the HAL bath.

Hope this helps,
Paul Gould
Teknacron Circuits Ltd
paul@bembridg.demon.co.uk
Isle of Wight,UK