Download Component Bonding and SMT Leads: Acceptable vs. Defect Criteria and more Exams Electrical Engineering in PDF only on Docsity!
Staking Adhesive - Component Bonding Acceptable - Class 1 Process Indicator - Class 2 - ANSWER Adhesive material extending from under the component is visible in the termination area, but end joint width meets minimum requirements Staking Adhesive - Component Bonding Defect - Class 3 - ANSWER Adhesive materials extending from under the component are visible in the termination area Staking Adhesive - Mechanical Strength Acceptable - Class 1,2,3 - ANSWER - On round components adhesive adheres to a minimum 25% of the component height
- On round components a minimum of three beads of staking material placed approximately evenly around the periphery of the component
- Slight flow under the component body does not damage the components or affect form, fit and function Staking Adhesive - Mechanical Strength Not Established - Class 1 Defect - Class 2,3 - ANSWER On round components there are less than three beads of staking material Staking Adhesive - Mechanical Strength Defect - Class 1,2,3 - ANSWER Adhesive is not completely cured and homogemous QUESTION**: SMT Leads - Plastic Components - ANSWER Unless otherwise specified, solder shall not touch a package body or seal. Expectations are when a copper lead or termination configuration causes the solder fillet to contact a plastic component body, such as:
- Plastic SOIC family (small outline packages such as SOT, SOD) SMT Leads - Damage Defect - Class 1,2,3 - ANSWER Lead is damaged or deformed more than 10% of the diameter, width or thickness of the lead SMT Leads - Flattening Acceptable - Class 1,
Defect - Class 3 - ANSWER The thickness of the flattened lead is less than 40% of the original diameter SMT Connections - ANSWER - Components with surface and/or termination ends or sides that are not wettable by design are exempt from solder wetting requirements in those areas. Solder fillet wetting to the sides or ends of the leads is not required unless specifically stated.
- Solder fillet may extend through the top bend. Solder should not extend under the body or surface mount components whose leads are made of Alloy 42 or similar metals. SMT Connections Acceptable - Class 1,2,3 - ANSWER Component titled/raised does not affect form, fit or function Chip Components - Bottom Only Terminations - Side Overhang (A) Acceptable - Class 1,2 - ANSWER Side overhang (A) is less than or equal to 50% width of component termination area (W) or 50% width of land (P), whichever is less Chip Components - Bottom Only Terminations - Side Overhang (A) Acceptable - Class 3 - ANSWER Side overhang (A) is less than or equal to 25% width of component termination area (W) or 25% width of land (P), whichever is less Chip Components - Bottom Only Terminations - End Joint Width (C) Acceptable - Class 1,2 - ANSWER Minimum end joint width (C) is 50% width of component termination (W) or 50% width of land (P), whichever is less Chip Components - Bottom Only Terminations - End Joint Width (C) Acceptable Class 3 - ANSWER Minimum end joint width (C) is 75% width of component termination (W) or 75% width of land (P), whichever is less Chip Components - Bottom Only Terminations - End Overlap (J) Acceptable - Class 2 - ANSWER End overlap (J) between the component termination and the land is minimum 50% the length of component termination (R) Chip Components - Bottom Only Terminations - End Overlap Acceptable - Class 3 - ANSWER End overlap (J) between the component termination and the land is minimum 75% the length of component termination (R) Rectangular or Square End Clip Components - 1,2,3 or 5 Termination(s) - Side Overhang (A)
Rectangular or Square End Chip Components - 1,2,3 or 5 Side Termination(s) - End Overlap (J) Defect - Class 1,2,3 - ANSWER Insufficient end overlap Rectangular or Square End Chip Components - 1,2,3 or 5 Side Termination(s) - End Overlap (J) Defect - Class 3 - ANSWER Less than 25% overlap contact (J) between the component termination and the land Rectangular or Square End Chip Components - 1,2,3 or 5 Side Termination(s) - Termination Variations - Mounting on Side (Billboarding) Acceptable - Class 1,2 - ANSWER Width (W) to height (H) ratio does not exceed two to one (2:1) ratio Rectangular or Square End Chip Components - 1,2,3 or 5 Side Termination(s) - Termination Variations - Mounting on Side (Billboarding) Acceptable - Class 3 - ANSWER For component size 1206 or smaller:
- Component has three or more termination faces (metallization) For components larger than size 1206:
- Component has five termination faces (metallization) Rectangular or Square End Chip Components - 1,2,3 or 5 Side Termination(s) - Termination Variations - Mounting on Side (Billboarding) Defect - Class 3 - ANSWER For component size 1206:
- Component has less than three termination faces (metallization) For components larger than size 1206:
- Component does not have five termination sides Rectangular or Square End Chip Components - 1,2,3 or 5 Side Termination(s) - Termination Variations - Mounting Upside Down Acceptable - Class 1 Process Indicator - Class 2,3 - ANSWER 1, 3, 5 side termination chip components with surface deposited electrical element is mounted toward the board Rectangular or Square End Chip Components - 1,2,3 or 5 Side Termination(s) - Termination Variations - Stacking Acceptable - Class 1,2,3 - ANSWER Side overhang does not preclude formation of required solder fillets Rectangular or Square End Chip Components - 1,2,3 or 5 Side Termination(s) - Termination Variations - Tombstoning Defect - Class 1,2,3 - ANSWER Chip components standing on a terminal end (tombstoning)
Rectangular or Square End Chip Components - 1,2,3 or 5 Side Termination(s) - Termination Variations - Center Terminations - Solder Width of Side Termination Acceptable - Class 1,2 - ANSWER Width of side termination(s) is minimum 50% of component termination width or 50% land width, whichever is less Rectangular or Square End Chip Components - 1,2,3 or 5 Side Termination(s) - Termination Variations - Center Terminations - Solder Width of Side Termination Acceptable - Class 3 - ANSWER Width of the side termination is minimum 75% of component termination or 75% land width, whichever is less Rectangular or Square End Chip Components - 1,2,3 or 5 Side Termination(s) - Termination Variations - Center Terminations - Minimum Fillet Height of Side Termination Acceptable - Class 1,2,3 - ANSWER Wetting is evident on the vertical surface(s) of the component side termination Cylindrical End Cap Terminations - ANSWER This component is sometimes referred to as MELF (Metal Electrode Leadless Face) Cylindrical End Cap Terminations - Side Overhang (A) Acceptable - Class 1,2,3 - ANSWER Side overhang (A) is 25% or less of the diameter of component width (W) or land width (P), whichever is less Cylindrical End Cap Terminations - End Overhang (B) Defect - Class 1,2,3 - ANSWER Any end overhang (B) Cylindrical End Cap Terminations - End Joint Width (C) Acceptable - Class 1 - ANSWER End solder joint exhibits a wetted fillet Cylindrical End Cap Terminations - Side Joint Length (D) Acceptable - Class 2 - ANSWER Side joint length (D) is minimum 50% length of component termination (R) or land length (S), whichever is less Cylindrical End Cap Terminations - Side Joint Length (D) Acceptable - Class 3 - ANSWER Side joint length (D) is minimum 75% length of component termination (R) or land length (S), whichever is less Cylindrical End Cap Terminations - Maximum Fillet Height (E) Defect - Class 1,2,3 - ANSWER Solder fillet extends onto the component body top Cylindrical End Cap Terminations - Minimum Fillet Height (F) Acceptable - Class 3 - ANSWER Minimum fillet height (F) is solder thickness (G) plus either 25% diameter (W) of the component end cap or 1 mm [0.04 in], whichever is less Cylindrical End Cap Terminations - Minimum Fillet Height (F)
Flat Gull Wing Leads - Side Overhang (A) Acceptable - Class 1,2 - ANSWER Maximum overhang (A) is not greater than 50% lead width (W) or 0.5 mm [0.02 in], whichever is less Flat Gull Wing Leads - Side Overhang (A) Acceptable - Class 3 - ANSWER Maximum overhang (A) is not greater than 25% lead width (W) or 0.5 mm [0.02 in], whichever is less Flat Gull Wing Leads - Toe Overhang (B) Acceptable - Class 2,3 - ANSWER Formed foot length (L) is greater than three lead widths (W) Flat Gull Wing Leads - Minimum End Joint Width (C) Acceptable - Class 1,2 - ANSWER Minimum end joint width (C) is 50% lead width (W) Flat Gull Wing Leads - Minimum End Joint Width (C) Acceptable - Class 3 - ANSWER Minimum end joint width (C) is 75% lead width (W) Flat Gull Wing Leads - Minimum Side Joint Width (D) Acceptable - Class 2,3 - ANSWER - When foot length (L) is greater than or equal to three lead widths (W), minimum side joint length (D) is equal to or greater than three lead widths (W) or 75% (L), whichever is longer
- When foot length (L) is less than three lead widths (W), minimum side joint length (D) is equal to 100% (L) **Flat Gull Wing Leads - Maximum Heel Fillet Height (E) Acceptable - Class 1,2,3 - ANSWER - Solder touches a plastic SOIC family of components (small outline packages such as SOT, SOD)
- Solder does not touch ceramic or metal component TOE DOWN CONFIGURATION - ANSWER Flat Gull Wing Leads - Minimum Heel Fillet Height (E) Acceptable - Class 2 - ANSWER - Where lead thickness (T) is equal to or less than 0.4 mm [0.015 in], the minimum heel fillet is solder thickness (G) + lead thickness (T)
- Where lead thickness (T) is greater than 0.4mm [0.015 in], the minimum heel fillet is solder thickness (G) + 50% lead thickness (T) Flat Gull Wing Leads - Minimum Heel Fillet Height (E) Acceptable Class 1,2,3 - ANSWER In the case of a toe-down configuration, the minimum heel fillet height (F) extends at least to the mid-point of the outside lead bend
Flat Gull Wing Leads - Coplanarity Defect - Class 1,2,3 - ANSWER Component lead(s) out of alignment (coplanarity) preventing the formation of an acceptable solder connection TOE DOWN CONFIGURATION (8-65) - ANSWER Mark (8-65) Round or Flattened (Coined ) Gull Wing Leads - Minimum Heel Fillet Height (F) Acceptable - Class 1,2,3 - ANSWER In the case of a toe-down configuration, the minimum heel fillet height (F) extends at least to the mid-point of the outside lead bend Round or Flattened (Coined ) Gull Wing Leads - Minimum Heel Fillet Height (F) Acceptable - Class 1 - ANSWER A wetted fillet is evident Round or Flattened (Coined ) Gull Wing Leads - Minimum Heel Fillet Height (F) Acceptable - Class 2 - ANSWER Minimum heel fillet height (F) is equal to solder thickness (G) plus 50% thickness of lead at joint side (T) Round or Flattened (Coined ) Gull Wing Leads - Minimum Heel Fillet Height (F) Acceptable - Class 3 - ANSWER Minimum heel fillet height (F) is equal to solder thickness (G) plus thickness of lead at joint side (T) **J-Leads - Toe Overhang (B) Acceptable - Class 1,2,3 - ANSWER Toe overhang (B) is an unspecified parameter J-Leads - Side Joint Length (D) Acceptable - Class 2,3 - ANSWER Side joint length (D) greater than or equal to 150% lead width (W)
- ANSWER - Criteria for components
- Criteria for unformed flat lug lead Surface Mount Area Array - ANSWER Area array process guidance is provided in IPC-7095, which contains recommendations, based from extensive discussion of process development issues Surface Mount Area Array - Solder Connections Acceptable - Class 1,2,3 - ANSWER BGA solder balls contact and wet the land forming a continuous elliptical round connection Surface Mount Area Array - Underfill/Staking - ANSWER Excess underfill for staking material does not
- ANSWER Solder connections conform to 8.3.12.3, see figure 8-169, and have reflowed showing wetting to the lands on all package levels
Acceptable - Class - ANSWER P-Style Connections - Minimum Side Overhang (A) Acceptable - Class 23 - ANSWER Surface Mount Connections Defect - Class 1,2,3 - ANSWER Note: Connectors need to meet form, fit and function requirements. A trial mating of connector to connector or to assembly may be required for final acceptance. Jumper Wires - ANSWER - Information concerning rework and repair can be found in IPC-7711/
- Wire selection (7.5.1), wire routing (7.5.2) and adhesive staking of wire (7.5.3) criteria are applicable to SMT jumper wires
- ANSWER For all lap solder connections described int his section the following conditions are acceptble:
- Insulation cleaance
- Evidence of
- Wire contour
- No fractures
- Wire overhang Jump Wires - SMT - Chip and Cylindrical End Cap Copm Acceptable Class 1,2,3 - ANSWER Jump Wires - SMT - Chip and Cylindrical End Cap Copm Defect Class 1,2,3 - ANSWER Wire soldered on top of chip component termination Jump Wires - SMT - Chip and Cylindrical End Cap Copm Gull Wing Accepatble Class 1,2,3 - ANSWER Wire
- ANSWER Wire and extends past knee of bend
- ANSWER - Wire
- The
- Wire
- Wire
- Wire Jumper Wires - SMT - ANSWER - For a land width (P) that is 6 mm [0.25 in] or larger, the wetted wire to land interface is at least two conductor diameters
- For a land width (P) less than 6 mm [0.25 in], the wetted wire to land interface is less than 50% of the land width or two conductor diameters, whichever is greater
- Conductor discernible in solder connection
