Electronics > Beginners

Solder mixture - 60/40 67/37

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tkamiya:
Although I've been in electronics for over 40 years, I never gave much thought to solders.  Now I'm wondering about something I'm sure many of you know....

Common lead-tin solder comes in 60/40 and 63/37 mixture.  What is the difference between the two.  Sure, melting point is a bit different by 5 degrees, but that's not much to make two different products.  There got to be more to it.

I've been using them interchangeably.  Can anyone share the secret?

sleemanj:
63/37 is eutectic, it melts and solidifies at a fairly precise temperature, in other words the transition from melted to solid happens much more quickly,  "melty...solid"  instead of 60/40 which is more "melty...a bit less melty... a little bit solid... getting pretty solid... ok we're done"

Simon_RL:

--- Quote from: sleemanj on January 18, 2020, 11:43:10 pm ---63/37 is eutectic, it melts and solidifies at a fairly precise temperature, in other words the transition from melted to solid happens much more quickly,  "melty...solid"  instead of 60/40 which is more "melty...a bit less melty... a little bit solid... getting pretty solid... ok we're done"

--- End quote ---

So for noobs 60/40 is definitely the better option as it is more forgiving.

Moshly:

--- Quote from: Simon_RL on January 19, 2020, 02:52:43 am ---
--- Quote from: sleemanj on January 18, 2020, 11:43:10 pm ---63/37 is eutectic, it melts and solidifies at a fairly precise temperature, in other words the transition from melted to solid happens much more quickly,  "melty...solid"  instead of 60/40 which is more "melty...a bit less melty... a little bit solid... getting pretty solid... ok we're done"

--- End quote ---

So for noobs 60/40 is definitely the better option as it is more forgiving.

--- End quote ---

Technically no, 60/40 has a longer time in the plastic (melty) state as its cooling down so the joint has to remain still for longer as you will get a dry joint if moved. For hobbyist it does not matter as you normally hold the part and watch the solder solidify before continuing.

tooki:

--- Quote from: Simon_RL on January 19, 2020, 02:52:43 am ---
--- Quote from: sleemanj on January 18, 2020, 11:43:10 pm ---63/37 is eutectic, it melts and solidifies at a fairly precise temperature, in other words the transition from melted to solid happens much more quickly,  "melty...solid"  instead of 60/40 which is more "melty...a bit less melty... a little bit solid... getting pretty solid... ok we're done"

--- End quote ---

So for noobs 60/40 is definitely the better option as it is more forgiving.

--- End quote ---
No, the exact opposite: 60/40’s plastic phase is a wider window of time during which the joint can be disturbed. This makes it LESS forgiving of movement during cooling.

60/40 is used because it is/was slightly cheaper, which mattered for mass production. But nowadays they usually cost the same, and IMHO there is no reason whatsoever to choose it over 63/37.

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