CIT Requirements for Soldered Electrical and Electronic Assemblies 2 — Questions and Answers
Question 1: According to IPC J-STD-001, what is the minimum solder coverage required on the lead end for Class 2 through-hole solder joints?
- 25%
- 50%
- 75%
- 100% (Correct answer)
Correct answer: 100%
IPC J-STD-001 requires 100% solder coverage on the lead end (top of the board) for Class 2 through-hole solder joints.
Question 2: Which flux type classification per J-STD-004 does NOT require cleaning after soldering when used within its activity level limits?
- OA (Organic Acid)
- IA (Inorganic Acid)
- RO (Rosin) (Correct answer)
- WS (Water Soluble)
Correct answer: RO (Rosin)
RO (Rosin) flux residues are generally considered non-corrosive and do not require cleaning when activity levels are within specified limits.
Question 3: What is the purpose of the 'wetting angle' measurement in solder joint evaluation?
- To measure the temperature of the solder joint
- To assess how well the solder has bonded and spread on the metal surface (Correct answer)
- To determine the volume of solder deposited
- To calculate the thermal resistance of the joint
Correct answer: To assess how well the solder has bonded and spread on the metal surface
The wetting angle (contact angle) indicates how well the solder has flowed and bonded to the base metal, reflecting the quality of the metallurgical bond.
Question 4: Per IPC J-STD-001, a 'cold solder joint' is characterized by which visual appearance?
- Bright, shiny, smooth surface
- Dull, grainy, or frosted surface indicating incomplete fusion (Correct answer)
- Convex meniscus with steep sides
- Excess solder forming a large fillet
Correct answer: Dull, grainy, or frosted surface indicating incomplete fusion
Cold solder joints appear dull, grainy, or frosted because the solder did not reach proper reflow temperature, resulting in poor tin-lead or tin alloy crystallization.
Question 5: What does the IPC J-STD-001 term 'minimum annular ring' refer to in PCB fabrication requirements?
- The ring of solder around a via
- The copper remaining between the drilled hole edge and the outer edge of the pad (Correct answer)
- The flux residue ring around a solder joint
- The clearance between two adjacent solder joints
Correct answer: The copper remaining between the drilled hole edge and the outer edge of the pad
The annular ring is the copper pad material remaining between the drilled hole and the outer edge of the pad, ensuring adequate mechanical and electrical connection.
Question 6: Which soldering iron tip condition is required before applying solder to ensure quality joints per workmanship standards?
- Dry and uncoated tip at maximum temperature
- Oxidized tip to improve heat transfer
- Properly tinned tip with fresh solder coating (Correct answer)
- Tip coated with flux gel
Correct answer: Properly tinned tip with fresh solder coating
A properly tinned soldering iron tip prevents oxidation, improves heat transfer efficiency, and produces consistent, high-quality solder joints.
Question 7: Per IPC J-STD-001, which condition is an ACCEPT criteria for a chip component (0402 or larger) solder joint side overhang?
- Overhang exceeds 50% of the component width
- Overhang is less than or equal to 25% of the component width (Correct answer)
- Any overhang is a defect regardless of size
- Overhang is permissible up to 75% for Class 1 only
Correct answer: Overhang is less than or equal to 25% of the component width
IPC J-STD-001 accepts side overhang of 25% or less of the component width for chip components as a process indicator (not a defect) for Class 1 and 2.
CIT Requirements for Soldered Electrical and Electronic Assemblies 2
According to IPC J-STD-001, what is the minimum solder coverage required on the lead end for Class 2 through-hole solder joints?