IPC Certified IPC Specialist (CIS) — Questions and Answers

Question 1: What is a 'measling' defect on a printed circuit board?

White spots or crosses below the surface of the base laminate caused by separation of glass fibers from the resin (Correct answer)
Micro-cracks in the solder mask coating
Surface contamination causing solder non-wetting
Delamination between copper layers and the substrate

Correct answer: White spots or crosses below the surface of the base laminate caused by separation of glass fibers from the resin

Measling appears as white spots or crosses beneath the laminate surface, caused by the separation of glass fibers from the resin binder, typically from thermal or mechanical stress.

Question 2: IPC-A-610 defines 'minimum electrical clearance' violations as:

Process indicators requiring documentation only
Defects for Class 2 and Class 3 only
Acceptable if no functional failure is detected
Defects for all classes (Correct answer)

Correct answer: Defects for all classes

Any violation of minimum electrical clearance between conductors is a defect for all IPC classes because it creates a risk of arcing, shorts, or dielectric breakdown.

Question 3: According to IPC-A-610, a 'process indicator' is best described as:

An anomaly that does not affect form, fit, or function but warrants monitoring (Correct answer)
A defect requiring mandatory rework before shipment
A critical safety hazard on the assembly
A condition that causes immediate product rejection

Correct answer: An anomaly that does not affect form, fit, or function but warrants monitoring

A process indicator is a condition that does not affect form, fit, or function but indicates the manufacturing process may be marginal and should be monitored.

Question 4: According to IPC-A-610, what is the maximum allowable percentage of a solder joint's height that may be voided for Class 2 SMT components?

10%
50%
25% (Correct answer)
No voids allowed

Correct answer: 25%

IPC-A-610 allows up to 25% voiding by area in solder joints for Class 2 assemblies when inspected by X-ray.

Question 5: What does 'DFM' stand for in PCB fabrication?

Defect-Free Manufacturing
Dielectric Film Measurement
Drill Feed and Motion
Design for Manufacturing (Correct answer)

Correct answer: Design for Manufacturing

DFM stands for Design for Manufacturing, the process of designing PCBs to be easily and reliably fabricated with minimal defects.

Question 6: What is 'pad cratering' in PCB assemblies?

Formation of voids in through-hole plating
Delamination of the copper foil from the board
Fracture within the PCB laminate beneath a surface pad (Correct answer)
Solder mask cracking under a pad

Correct answer: Fracture within the PCB laminate beneath a surface pad

Pad cratering is a fracture in the PCB laminate directly below the copper pad, often caused by mechanical stress during assembly or testing.

Question 7: What does 'ESD susceptibility' of a component refer to?

The rate at which a component dissipates accumulated static charge
The component's ability to generate static electricity during operation
The component's resistance to ESD-induced latch-up
The voltage threshold below which the component can be damaged by electrostatic discharge (Correct answer)

Correct answer: The voltage threshold below which the component can be damaged by electrostatic discharge

ESD susceptibility refers to the minimum voltage level that can damage a component, with more susceptible devices being damaged at lower ESD voltages.

Question 8: Which ESD failure mode occurs when a device appears to function but has hidden latent damage from a prior ESD event?

Catastrophic failure
Latent defect (Correct answer)
Parametric failure
Hard failure

Correct answer: Latent defect

A latent defect is hidden damage from an ESD event that does not immediately cause failure but may cause the device to fail prematurely in the field.

Question 9: What is the typical surface resistance range for ESD dissipative materials?

1 × 10² to 1 × 10³ ohms/square
1 × 10⁴ to 1 × 10¹¹ ohms/square (Correct answer)
Less than 1 × 10³ ohms/square
Greater than 1 × 10¹² ohms/square

Correct answer: 1 × 10⁴ to 1 × 10¹¹ ohms/square

ESD dissipative materials have a surface resistance of 1 × 10⁴ to 1 × 10¹¹ ohms/square, allowing slow, controlled discharge of static charges.

Question 10: For IPC Class 3, a lifted land (pad lifting from the board surface) on a through-hole component is:

A process indicator requiring documentation
Acceptable if solder joint strength is maintained
A defect (Correct answer)
Acceptable if less than 25% of the land is lifted

Correct answer: A defect

For IPC Class 3 high-reliability products, any lifted land is a defect because it compromises the reliability of the solder connection.

Question 11: According to IPC-A-610, which condition constitutes a defect for all classes regarding component body damage?

Cracking that exposes internal component material (Correct answer)
Minor surface scratches on the component body
Discoloration of the component body from heat
Damaged component markings that are still partially readable

Correct answer: Cracking that exposes internal component material

Cracking that exposes the internal material of a component body is a defect for all IPC classes because it compromises component integrity and reliability.

Question 12: During wave soldering, what is the function of the preheater section?

Cool the board after soldering
Activate flux and bring the board near soldering temperature (Correct answer)
Melt solder in the bath
Apply solder mask

Correct answer: Activate flux and bring the board near soldering temperature

The preheat section activates flux, evaporates solvents, and raises PCB temperature to reduce thermal shock during wave contact.

Question 13: 'Dewetting' in soldering refers to:

A base metal surface that has been oxidized prior to soldering
The process of removing flux residue after soldering
Solder that wetted a surface but then partially pulled back, leaving an uneven, irregular surface (Correct answer)
Solder that has not melted sufficiently during the soldering process

Correct answer: Solder that wetted a surface but then partially pulled back, leaving an uneven, irregular surface

Dewetting occurs when solder initially wets a surface but then contracts or pulls back, leaving irregular solder masses separated by areas where the base metal is exposed.

Question 14: What does the term 'annular ring' refer to on a printed circuit board?

The clearance between a via and a ground plane
The plating thickness inside a via
The solder mask opening around a pad
The copper remaining on a pad after drilling (Correct answer)

Correct answer: The copper remaining on a pad after drilling

The annular ring is the portion of conductive material (copper) that remains on a pad after a hole has been drilled through it.

Question 15: Which test verifies the registration accuracy of drilled holes to their corresponding pads on a PCB?

Coupon cross-section analysis
X-ray inspection (Correct answer)
Peel strength test
Microsection analysis

Correct answer: X-ray inspection

X-ray inspection is used to verify drill-to-pad registration and check internal layer alignment without destructive sectioning.

Question 16: Which handling practice is required when working with beryllium copper (BeCu) component leads?

Wear gloves and avoid creating dust or particles — BeCu is a health hazard (Correct answer)
Heat the leads before bending to prevent cracking
Apply dielectric grease to prevent oxidation
No special precautions beyond standard ESD handling

Correct answer: Wear gloves and avoid creating dust or particles — BeCu is a health hazard

Beryllium copper dust and particles are highly toxic; OSHA regulations require gloves, respiratory protection, and specific disposal procedures when machining or bending BeCu components.

Question 17: What is 'dewetting' in soldering, and how does it differ from 'non-wetting'?

Dewetting applies only to through-hole joints; non-wetting applies to SMT only
Dewetting and non-wetting are interchangeable terms in IPC standards
Dewetting is when molten solder initially wets then recedes, leaving a rough irregular surface; non-wetting means solder never adhered (Correct answer)
Dewetting means the solder never melted properly; non-wetting means it melted but didn't flow

Correct answer: Dewetting is when molten solder initially wets then recedes, leaving a rough irregular surface; non-wetting means solder never adhered

Dewetting indicates the base metal surface was initially solderable but became contaminated or oxidized, while non-wetting means adhesion never occurred.

Question 18: According to IPC-2221, which laminate property most directly affects the dielectric constant of a PCB?

Copper weight
Peel strength
Glass transition temperature (Tg)
Resin content (Dk) (Correct answer)

Correct answer: Resin content (Dk)

The resin content and dielectric constant (Dk) of the laminate material directly determine the board's dielectric constant.

Question 19: According to ANSI/ESD S20.20, floor materials in an ESD Protected Area must have a resistance-to-ground of no more than:

1 × 10¹¹ ohms
1 × 10¹² ohms
1 × 10⁹ ohms (Correct answer)
1 × 10⁷ ohms

Correct answer: 1 × 10⁹ ohms

ANSI/ESD S20.20 requires ESD flooring to have a resistance-to-ground of no more than 1 × 10⁹ ohms (1 gigaohm) to ensure static charge dissipation.

Question 20: Which process uses localized heat to solder individual through-hole components while protecting SMT components on the same board?

Vapor phase soldering
Dip soldering
Reflow soldering
Selective soldering (Correct answer)

Correct answer: Selective soldering

Selective soldering applies solder only to designated areas using a miniature solder wave or laser, protecting nearby SMT components.

Question 21: For IPC-A-610 Class 3, what is the acceptability status of a pinhole or blowhole in a solder joint?

Defect (Correct answer)
Acceptable if only one per joint
Acceptable if the hole diameter is less than 0.5 mm
Process indicator

Correct answer: Defect

Pinholes and blowholes in solder joints are defects for Class 3 assemblies because they indicate voiding and potential joint weakness.

Question 22: What is the correct interpretation of a 'target condition' in IPC-A-610?

The minimum acceptable condition for product acceptance
The condition requiring mandatory rework
The marginal condition that triggers a process review
The ideal, preferred condition showing a high degree of workmanship (Correct answer)

Correct answer: The ideal, preferred condition showing a high degree of workmanship

A target condition in IPC-A-610 represents the ideal, preferred result demonstrating a high degree of workmanship — it is not the minimum acceptable standard.

Question 23: What is the purpose of a control chart in a PCB assembly quality system?

To track process variation over time and detect out-of-control conditions (Correct answer)
To certify that solder paste meets J-STD-005 requirements
To record the AQL level applied to each production lot
To document all non-conforming units found during final inspection

Correct answer: To track process variation over time and detect out-of-control conditions

Control charts (SPC tools) monitor process metrics over time, enabling detection of trends or special-cause variation before defects are produced.

Question 24: What is 'head-in-pillow' (HiP) defect in BGA soldering and what primarily causes it?

The BGA package shifts during reflow causing misaligned balls
The solder ball and paste solder solidify separately without fully coalescing, often due to oxidation or insufficient flux activity at peak temperature (Correct answer)
The PCB warps under the BGA, lifting it away from the board
Excess solder paste bridges adjacent BGA balls

Correct answer: The solder ball and paste solder solidify separately without fully coalescing, often due to oxidation or insufficient flux activity at peak temperature

HiP occurs when the ball and paste fail to merge during reflow, creating a non-wetted interface that may pass visual/X-ray inspection but fails electrically.

Question 25: What conformal coating defect is described as small circular depressions or craters that expose the underlying substrate?

Orange peel
Fisheye (cratering) (Correct answer)
Blooming
Delamination

Correct answer: Fisheye (cratering)

Fisheyes or cratering are circular depressions caused by surface tension differences, often from contamination or silicone, that pull the wet coating away from a point and expose the substrate.

Question 26: ESD training for personnel working in an EPA should be conducted:

Only when an ESD-related failure is detected
At initial hire and refreshed at least annually (Correct answer)
Once at initial hire only
Every 5 years or when job duties change

Correct answer: At initial hire and refreshed at least annually

ANSI/ESD S20.20 requires initial ESD training upon hire and annual refresher training to maintain awareness and compliance.

Question 27: What is 'controlled impedance' in PCB design?

Maintaining consistent trace resistance across temperature
Designing traces to a specific characteristic impedance value (Correct answer)
Limiting current density on high-power traces
Controlling the dielectric constant of the solder mask

Correct answer: Designing traces to a specific characteristic impedance value

Controlled impedance means designing PCB traces to achieve a specific characteristic impedance (e.g., 50Ω) to ensure signal integrity.

Question 28: What is the primary purpose of flux in the soldering process, and why must residues be managed?

Flux prevents tombstoning; residues attract moisture and cause delamination
Flux removes oxides to promote solder wetting; ionic residues can cause corrosion and leakage currents if not cleaned (Correct answer)
Flux acts as a bonding agent; residues increase mechanical strength of joints
Flux improves heat transfer; residues can crack solder joints when hardened

Correct answer: Flux removes oxides to promote solder wetting; ionic residues can cause corrosion and leakage currents if not cleaned

Flux removes oxides to enable proper solder wetting; however, ionic flux residues left on the board can absorb moisture and cause electrochemical corrosion and leakage currents.

Question 29: Which IPC standard specifically addresses the acceptability of electronic assemblies?

IPC-A-610 (Correct answer)
IPC-2221
IPC-A-600
IPC-7711

Correct answer: IPC-A-610

IPC-A-610, Acceptability of Electronic Assemblies, is the most widely used electronics assembly standard defining workmanship criteria.

Question 30: The glass transition temperature (Tg) of a PCB laminate is important because:

It indicates the temperature at which the laminate transitions from rigid to soft (Correct answer)
It determines the minimum drill bit diameter required
It defines the maximum copper plating thickness
It sets the maximum current-carrying capacity of traces

Correct answer: It indicates the temperature at which the laminate transitions from rigid to soft

Tg is the temperature at which the PCB laminate transitions from a rigid, glassy state to a softer, rubbery state, affecting reliability during thermal excursions.

Question 31: What action should be taken when a component's floor life timer has expired before it could be soldered?

Discard the component regardless of its condition
Bake the component per J-STD-033 baking schedule before soldering (Correct answer)
Use the component immediately, as floor life limits have safety margins
Reseal it in a moisture barrier bag and reset the timer

Correct answer: Bake the component per J-STD-033 baking schedule before soldering

Per J-STD-033, components with expired floor life must be baked per the prescribed time/temperature schedule to drive out absorbed moisture before soldering.

IPC Certified IPC Specialist (CIS)

The CIS certification validates knowledge of IPC standards for electronics manufacturing, covering acceptability criteria, PCB fabrication, ESD control, and rework/repair procedures for electronic assemblies.

100

Questions

150 min

Time Limit

70%

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