Deep Dive: T7D08
The correct answer is A: Acid-core solder. Acid-core solder should not be used for radio and electronic applications. Acid-core solder contains an acid flux that is corrosive and can damage electronic components, circuit boards, and connections over time. The acid residue left after soldering continues to corrode, causing failures. For amateur radio operators, only rosin-core solder (or water-soluble flux for some applications) should be used for electronics work. Acid-core solder is for plumbing and other non-electronic applications where the corrosive flux helps clean metal but won't damage the work.
Why Other Answers Are Wrong
Option B (Lead-tin solder): Incorrect. Lead-tin solder (typically 60/40 or 63/37) is commonly used in electronics, though lead-free alternatives are now preferred for environmental reasons. It's safe for electronics. Option C (Rosin-core solder): Incorrect. Rosin-core solder is the standard for electronics work. The rosin flux is non-corrosive and safe for electronic components. Option D (Tin-copper solder): Incorrect. Tin-copper solder is a lead-free alternative that's safe for electronics. It's commonly used in modern electronics manufacturing.
Exam Tip
Acid-core solder = NOT for electronics. Think 'A'cid-core = 'A'void in electronics. The acid flux is corrosive and damages components. Use rosin-core or lead-free solder for electronics.
Memory Aid
Acid-core solder = Avoid in electronics. Think 'A'cid-core = 'A'void. Corrosive flux damages electronic components. Use rosin-core or lead-free solder for electronics work.
Real-World Example
You use acid-core solder to repair a circuit board. The acid flux cleans the connection well initially, but over time the acid residue corrodes the copper traces and component leads, causing the circuit to fail. Using rosin-core solder would have been safe - the rosin flux is non-corrosive and designed for electronics. Acid-core is only for plumbing.
Source & Coverage
Question Pool: 2022-2026 Question Pool
Subelement: T7D
Reference: 2022-2026 Question Pool · T7 - Practical circuits
Key Concepts
Verified Content
Question from the official FCC Technician Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the T7D topic.