user43136: So this is the second time that I've had a circuit that worked perfectly on a breadboard, but as soon as I connected it to a perfboard and soldered the joints together, the Arduino stopped working and wouldn't let me upload sketches (though I could see a COM port for it).
I'm using lead-free solder for the first time, and had the temperature at 750 deg Fahrenheit, and I'm thinking that while I had quick joints to connect the Arduino to the perfboard, when bridging two joints with solder, the iron might have been heating the header pin for 4-10 seconds... Is that enough to break the board?

(note - I'm using jumper wires on the other side to connect everything up, and I've already checked the board's connections using a multimeter and they're all as intended, and there are no accidental shorts/bridges)

user612: 
I would like to clarify that my only question in ENTIRE post was: "Is that enough to break the board?" 

The answer to that narrow question is that heat from soldering with an iron is extremely unlikely to have done this.  IC's are in practice (vs data sheet) quite heat tolerant, and further the pins you are soldering on are not even the pins of the IC or any electronic components, but rather those of the module headers.  You'd be more likely to melt the plastic web between those headers pins, but even that won't be a great problem since they are already in place. Or if you were soldering directly on the board, lifting a pad or trace - but you were not doing that.
Your actual problem is something else, what that might be is presently unanswerable due to the lack of detail in your question.

43136: <p>So this is the second time that I've had a circuit that worked perfectly on a breadboard, but as soon as I connected it to a perfboard and soldered the joints together, the Arduino stopped working and wouldn't let me upload sketches (though I could see a COM port for it).</p>

<p>I'm using lead-free solder for the first time, and had the temperature at 750 deg Fahrenheit, and I'm thinking that while I had quick joints to connect the Arduino to the perfboard, when bridging two joints with solder, the iron might have been heating the header pin for 4-10 seconds... Is that enough to break the board?</p>

<p><a href="https://i.stack.imgur.com/rVYSK.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/rVYSK.jpg" alt="my perfboard joints"></a></p>

<p>(note - I'm using jumper wires on the other side to connect everything up, and I've already checked the board's connections using a multimeter and they're all as intended, and there are no accidental shorts/bridges)</p>
 612: <blockquote>
  <p>I would like to clarify that my only question in ENTIRE post was: "Is that enough to break the board?" </p>
</blockquote>

<p>The answer to that narrow question is that <em>heat from soldering with an iron</em> is extremely unlikely to have done this.  IC's are in practice (vs data sheet) quite heat tolerant, and further the pins you are soldering on are not even the pins of the IC or any electronic components, but rather those of the module headers.  You'd be more likely to melt the plastic web between those headers pins, but even that won't be a great problem since they are already in place. Or if you were soldering directly on the board, lifting a pad or trace - but you were not doing that.</p>

<p>Your actual problem is something else, <em>what that might be</em> is presently unanswerable due to the lack of detail in your question.</p>
