When soldering PCBs, I often go through this familiar cycle: finish soldering, power up the board, discover it doesn’t work, and then immediately suspect that maybe one of the chips got damaged by excessive heat during soldering. What follows is a long cycle of swapping components, re-soldering, probing, and measuring—until the board is a burnt, messy battlefield, and the problem still remains.
More often than not, the real issue isn’t a damaged chip—it’s a mistake in the design: maybe the schematic is wrong, the power rails are reversed, the components were misselected, or the footprint pins are incorrectly mapped. After repeating this scenario enough times, I began to question that knee-jerk reaction: “Did I fry the IC with my soldering iron?”
The short answer is: in most cases, no, you didn’t.
A Simple Rule of Thumb
It’s actually quite easy to judge whether a chip might have been heat-damaged during soldering. There’s a very practical rule of thumb:
If the soldering temperature was high enough to damage the IC, the PCB would likely show signs of scorching or charring first.
In other words, between the PCB and the IC, the PCB is usually the weaker link. FR4 boards begin to yellow and char above 200°C, and at temperatures above 300°C, the board can blister or even burn after just a few seconds. In contrast, most SMD ICs are rated to tolerate reflow soldering at around 350–400°C for short durations (typically 3–4 seconds) without damage.
So here’s the key takeaway:
If your PCB looks intact, your IC is probably fine.
Why Soldered Boards Fail
When a newly soldered board “does nothing” after powering on, the real causes are often:
- Errors in the schematic (e.g., reversed power supply, incorrect signal routing)
- Signal integrity issues (e.g., reflections, ringing, improper impedance matching)
- Cold joints, weak solder connections, or solder bridges
- Wrong power rail voltage—ICs not powered at all
- Incorrect part selection or mismatched footprints
Compared to these, “soldering iron temperature was too high and damaged the IC” is an extremely rare cause. Over-focusing on that possibility can actually lead you down the wrong troubleshooting path and waste a lot of time.