[Elecraft] Solder Question...

Wed May 28 09:29:01 2003

Trevor -

Excellent question. This topic was covered in an old QST article (1960s, I 
believe).

The 63/37 alloy is the tin-lead eutectic and is used in printed circuit board 
manufacturing where temperature limitations are critical and in applications 
where an extremely short melting range is required.  A "eutectic" is the 
specific alloy mixture with the lowest melting temperature [361 F. / 183 C. 
degrees].

Here is Kester's Alloy temperature chart.
http://www.kester.com/alloy_temp_chart.html

The 63/37 alloy has a single melting point - 361 F / 183 C. 
Other alloys, as can be seen inthe Kester alloy chart have "pasty" semi-solid 
temperature ranges(e.g. For 60/40 alloy range is 361 to 374 degrees).  
Solder joints that are physically or mechanially moved when cooling through 
this temperature range have a tendency to crystalize or become cold solder 
joints.  
This is why the 63/37 alloy is recommended for double sided, plated through 
hole boards and any boards with surface mount components.  The 63/37 flows 
better through holes and around the small SMT components.

The 60/40 alloy is very popular and is used in electrical work -- more 
specifically on single sided board technology. It is also preferred for solder 
dipping operations as it imparts a smooth finish.

Greg
w9gb
-------------------

Message: 28

From: "Trevor Jacobs" <[email protected]>
To: "Elecraft Mailing List" <[email protected]>
Date: Wed, 28 May 2003 00:28:14 -0700
Subject: [Elecraft] Solder Question...

Hey Gang,

I've always used 60/40 alloy solder (or 2% Silver for SMT) , but was
wondering about the 63/37 alloy? Was wondering what the purpose of the
different alloys was, other than the melting point (190 C for 60/40 and
183 C for 63/37). Is one more preferable for rework?

Also, anyone have a mail order/on-line source for Multicore solder? I
used my last roll up about a year ago and had been using Kester 60/40
#44 Flux and really liked the Multicore better. After checking the
Locktite web site, they don't seem to mention any part numbers, and
looks as though they are concentrating more on the "Lead Free" stuff. In
fact the only "Multicore" solder wire they mention in the product sheet
all has either "No Clean" or "Water Washable" Flux. Digikey doesn't have

it either. I wonder if this "Lead Free" stuff is going to take over?
Anyway, any information is appreciated.

73's Trev KG6CYN
http://www.qsl.net/kg6cyn