Philip,

Are you talking about the physical process of converting the solder bath over
or re-optimising the process after the change?    And I presume by solder dip
you mean wave or flow soldering.

The only issue in the physical changeover of a wave soldering machine is
ensuring that all residues of the lead solder are removed.    That requires
removal of the pump and nozzle assembly and dismantling as far as possible.
Then it has been found to be worthwhile rinsing the solder bath and all the
parts that come in contact with the solder in pure tin.   You do not need to
fill up the bath completely but there should be sufficient molten tin to
provide an adequate rinse.   Typically 100kg of tin is used.    Unless it is
heavily contaminated that tin can be reused in converting other solder baths
to leadfree.

In reviewing whether a wave soldering machine is suitable for use with
leadfree solder preheat capacity is a consideration.   If you are soldering
through-hole boards you may need up to 130C topside preheat to get a topside
fillet if there are areas of high thermal mass.   And since the solder bath
temperature is closer to the melting point of the solder than it is with
conventional tin-lead solder you need to be sure that the heating system can
keep all parts of the pot at temperature to a reasonably close tolerance.
In fact control of all process parameters needs to be fairly good as you are
working within a narrower tolerance than you have with conventional tin-lead
solder.

Regards
Keith Sweatman
Nihon Superior Co Ltd

---------------------------------------------------------------------------------
Leadfee Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Leadfree
To temporarily stop delivery of Leadree for vacation breaks send: SET Leadfree NOMAIL
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
---------------------------------------------------------------------------------