#PCB Engineers, let's test your eyes.
At first glance, all four solder joints look acceptable.
But only one of them is a true cold solder joint.

Cold solder defects can lead to:
▪ Increased contact resistance
▪ Intermittent electrical connections
▪ Reduced mechanical strength
▪ Early field failures

The challenge is that they don't always look obvious.
In real production environments, engineers often need to distinguish subtle differences in surface texture, wetting behavior, and solder appearance to identify potential reliability risks.

👇 What's your answer?
A, B, C, or D?
And more importantly...
What clues helped you make your decision?