Charlie,

It seems you are soldering with what is referred to as HMP
solder,(94Pb/5Sn/1AG).  There are several similar compositions in the
neighborhood such as 95Pb/5Sn and 93Pb/5Sn/2Ag.  They solders like other high
lead solders at about 700F (385C) iron and with  a ceramic substrate,
probably aluminum oxide there is no problem .   Some people like to use a bit
higher temperature iron and get on and get off quicker.  The appearance of
the joint is not as shiny as the tin-lead eutectic solder and may appear
grainy.  It is desirable to raise the temperature of the substrate by putting
it on a hot plate at about 230 to 250 C. and pretin the lands with the
solder.  Use a lower temperature on the hot plate during soldering of about
200-225 C and do it fairly rapidly as the high-lead solder oxidizes rapidly.
 You  can also solder without using a hot plate, but it takes considerable
longer ti get the board up to up to soldering temperature.  If you are using
tin/lead coated component leads these must be stripped and recoated or the
joints will let loose at 180C, just recoating by dipping will not do it,
either chemically strip or use turbulent wave retinning operation.  The flux
can be RA, RMA or OA  whatever you are comfortable with, but query the
supplier as to his activation temperature and degradation of activator
temperature.

The electroless nickel/immersion gold finiosh on copper lands works well with
the HMP solder and to my best knowledge is not subject to the problems that
have been reported with the this plating system is soldered with tin-based
solders and then used at higher operating temperatures.

I do not umderstand you reference to Pl/Pt/Au since the Pl is not an element
that is listed in the periodic chart.

If you want to SMT reflow solder,  I understand Innova Electronics Inc. of
Houston,TX 713-690-9909, an assembly house, will do it with HMP solders.

Pull strength is usually based on the land to substrate strength, and the way
you pull it is important, it can be either peel, shear or tensile.  Usually
the land will come off before the solder fails, but if you have other
conditons, they will pop off at about 25% of the land to substrate stength.
 Look at IPC-TM-650 Method 2.4.21.1 as a pull strength method.  I usually use
Sn63 without any thermal aging as comparison test piece.

Phil Hinton

##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE TECHNET <your full name>
To unsubscribe:   SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information.
For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311
##############################################################