Anil K Singh wrote:-
>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.

Hello Anil,

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
[log in to unmask]
Isle of Wight,UK

***************************************************************************
* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
***************************************************************************
* To subscribe/unsubscribe send a message <to: [log in to unmask]>   *
* with <subject: subscribe/unsubscribe> and no text in the body.          *
***************************************************************************
* If you are having a problem with the IPC TechNet forum please contact   *
* Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask]      *
***************************************************************************