Surface Mount Component Families

Message Topic Search Topic Options Post Reply Create New Topic Printable Version Translate Topic

   Chips
Chips: An ultra-compact rectangular housing designed specifically for surface mount discrete passive or semiconductor devices containing exactly two electrical terminals. Electrical contacts are located at opposite ends of the body, wrapping around the edges to form metallized soldering pads. Most 2-pin passive chips are physically symmetrical, allowing automated pick-and-place systems to orient them easily without top-to-bottom or front-to-back errors. The body typically consists of a single block of ceramic (for capacitors), thick-film substrate (for resistors), or molded plastic/glass (for diodes).

Monolithic Structure: The body typically consists of a single block of ceramic (for capacitors), thick-film substrate (for resistors), or molded plastic/glass (for diodes).

Rectangular or Square End-Cap Terminations: Electrical contacts are located at opposite ends of the body, wrapping around the edges to form metallized soldering pads.

Symmetrical Design: Most 2-pin passive chips are physically symmetrical, allowing automated pick-and-place systems to orient them easily without top-to-bottom or front-to-back errors.

  Chip Size Codes
  with Inch Dimensions

  EIA Inch
  (IEC Metric)

  Inch Dimensions

  01005 (0402)

  0.0157 in × 0.0079 in

  0201 (0603)

  0.024 in × 0.012 in

  0402 (1005)

  0.039 in × 0.020 in

  0603 (1608)

  0.063 in × 0.031 in

  0805 (2012)

  0.079 in × 0.049 in

  1008 (2520)

  0.098 in × 0.079 in

  1206 (3216)

  0.126 in × 0.063 in

  1210 (3225)

  0.126 in × 0.098 in

  1806 (4516)

  0.177 in × 0.063 in

  1812 (4532)

  0.180 in × 0.130 in

  2010 (5025)

  0.197 in × 0.098 in

  2512 (6332)

  0.250 in × 0.130 in

  2920 (7451)

  0.290 in × 0.200 in

  Chip Size Codes
  with Metric Dimensions

  IEC Metric (EIA
  Inch)

  Metric
  Dimensions

  0402 (01005)

  0.40 mm × 0.20 mm

  0603 (0201)

  0.60 mm × 0.30 mm

  1005 (0402)

  1.00 mm × 0.50 mm

  1608 (0603)

  1.60 mm × 0.80 mm

  2012 (0805)

  2.00 mm × 1.25 mm

  2520 (1008)

  2.50 mm × 2.00 mm

  3216 (1206)

  3.20 mm × 1.60 mm

  3225 (1210)

  3.20 mm × 2.50 mm

  4516 (1806)

  4.50 mm × 1.60 mm

  4532 (1812)

  4.50 mm × 3.20 mm

  5025 (2010)

  5.00 mm × 2.50 mm

  6332 (2512)

  6.40 mm × 3.20 mm

  7451 (2920)

  7.40 mm × 5.10 mm

Performance & Manufacturing Challenges

Tombstoning Risk: Because these chips have only two terminals, an imbalance in surface tension during solder reflow can cause the component to lift off one pad and stand vertically like a tombstone. This is minimized by maintaining perfectly symmetrical landing pads and thermal reliefs.

Ultra-Low Parasitics: The absence of long lead wires reduces parasitic inductance and capacitance, making these packages ideal for high-speed signal integrity and high-frequency RF layouts.

High-Speed Placement: Their flat, symmetrical shapes make them highly optimized for automated vacuum pick-and-place nozzles, allowing assembly machines to shoot thousands of these components per minute.

Molded Body

Molded Body: Electronic component housings formed by encapsulating internal elements (such as a silicon die, a capacitor element, or a lead frame) in a solid, injection-molded thermoset plastic or epoxy resin. Unlike generic ceramic or open-frame structures, these packages provide an airtight, structurally rigid shield that safeguards components against moisture, physical impact, and operational vibration. 

Inward L-Bend Lead: The leads curl tightly underneath the molded plastic shell. This saves valuable PCB area, though it hides the solder joints from easy optical inspection.

Heel and Toe Goals: IPC guidelines dictate robust calculation values for the Toe (outer edge) and Heel (inner edge) of the pad. These parameters ensure that the solder fillet achieves high mechanical joint strength.

Side Goal Omission: For many molded body components – specifically those utilizing Inward L-Bends – IPC standards omit a side-joint goal requirement. Adding extra pad width along the sides does not increase mechanical hold. Furthermore, excess side solder can cause the component to float or rotate out of alignment during the reflow oven cycle.

  Common
  Molded Body Tantalum Capacitors

  EIA
  Size Code

  Package
  Dimensions

  KEMET
  Code

  AVX
  Code

  2012-12

  2.00 x 1.30 x 1.20

  R

  R

  3216-10

  3.20 x 1.60 x 1.00

  I

  K

  3216-12

  3.20 x 1.60 x 1.20

  S

  S

  3216-18

  3.20 x 1.60 x 1.80

  A

  A

  3528-12

  3.50 x 2.80 x 1.20

  T

  T

  3528-21

  3.50 x 2.80 x 2.10

  B

  B

  6032-15

  6.00 x 3.20 x 1.50

  U

  W

  6032-28

  6.00 x 3.20 x 2.80

  C

  C

  7260-38

  7.30 x 6.00 x 3.80

  E

  V

  7343-20

  7.30 x 4.30 x 2.00

  V

  Y

  7343-31

  7.30 x 4.30 x 3.10

  D

  D

  7343-43

  7.30 x 4.30 x 4.30

  X

  E

Key Physical Features
Fully Encapsulated Core: Thermoset epoxy compound forms a solid protective layer on all sides, completely insulating the sensitive inner structures (such as silicon dies, wound wires, or sintered tantalum pellets) from environmental elements.
Integrated Polarity Markers: Because the body is formed in an injection-molding process, bevels, chamfered corner notches, or deep laser-etched bands are built directly into the plastic to indicate polarity (essential for diodes and tantalum caps).
Wrap-Around or Inward Terminations: Leads typically exit the bottom or centerline of the plastic molding and are bent flat against the body ends or tucked flush as leadless bottom contacts.
Classifications & Examples: Molded body packages use unique design rules and prefixes to accurately map their footprint requirements.

Tantalum Capacitors (CAPMP / EIA Standard): Features highly standardized molded packages categorized by standard uppercase lettering.
A Case (3216 Metric): 3.20 mm x 1.60 mm nominal
B Case (3528 Metric): 3.50 mm x 2.80 mm nominal
C Case (6032 Metric): 6.00 mm x 3.20 mm nominal
D Case (7343 Metric): 7.30 mm x 4.30 mm nominal

Diodes (DIOM / JEDEC DO-214): Molded discrete diodes leverage robust, wide wrap-around terminal feet built to absorb thermal stress.
SMA (DO-214AC): Smallest common molded diode variant
SMB (DO-214AA): Medium profile option
SMC (DO-214AB): Largest footprint format supporting high power surge ratings

Engineering Design Parameters: When laying out a land pattern for a molded body part with Footprint Expert use distinct math models.
Molded Body Side Goal: Footprint generation tools use a unique variable known as the "Molded Body Side Goal" to ensure the copper landing pads extend far enough beyond the side boundaries of the plastic block, keeping the solder joint from bridging or starving.
Heel Fillet Compensation (Jh): Because molded leads often tuck close or underneath the plastic shell, the heel fillet calculations must account for package chamfering to prevent cold solder joints or component tilt.
Robust Placement Courtyard: Since the molding process can incur minor edge tolerances (+/-0.2 mm package deviations), the IPC placement courtyard boundary must be generous enough to account for physical variations during automated assembly pick-and-place tracking.

Performance Advantages
High Moisture Resistance: Direct plastic encapsulation eliminates internal air pockets, effectively blocking moisture ingress and saving parts from internal corrosion or short circuits.
Structural Resistance to Shock: The solid core cushions internal components from physical drops, heavy vibrations, and handling damage during rapid assembly lines.
Perfect Coplanarity Control: Flat molded bottoms provide a highly stable seating plane during reflow, significantly reducing defects like skewing or uneven floating.
Cost Efficiency: Plastic transfer molding remains the most affordable, mass-producible chip encapsulation method in modern electronics manufacturing

Metal Electrode Leadless Face (MELF)

Metal Electrode Leadless Face (MELF): A specialized surface mount component package characterized by a cylindrical body with metallized round end caps. Unlike standard rectangular chip components, MELF packages are round and do not use traditional leads. They are primarily used for high-reliability resistors, fuses and diodes where superior thermal stability, low noise, and excellent moisture resistance are required.

Cylindrical Body: The housing is a glass or ceramic tube, making it highly resistant to thermal shock and moisture

Leadless Endcaps: Metal caps wrap around the circular edges on both ends, serving as the soldering terminals.

No Orientation Issues: Because it is perfectly round, the component can rotate along its long axis during placement without affecting its electrical connection.

Superior Reliability: MELF components offer exceptionally low failure rates and excellent long-term stability under harsh conditions.

High Thermal & Power Handling: The cylindrical shape provides a larger surface area than flat chips, allowing better heat dissipation and higher power ratings.

Low Noise & Parasitic: Excellent for high-frequency or high-precision circuits due to minimal structural inductance and capacitance.

  Common MELF Package Sizes

  Common Case Names

  Size Code

  Package Dimensions

  MicroMelf
  (MMU)

  0102

  2.20 L x 1.10 Dia.

  MiniMelf
  (MMA)

  0204

  3.60 L x 1.40 Dia.

  Melf
  (MMB)

  0207

  5.80 L x 2.20 Dia.

Small Outline Diode (SOD) with Gullwing Leads

Small Outline Diode (SOD) with Gullwing Leads: A standard surface mount semiconductor package designed for discrete components like switching, Schottky, and Zener diodes. 

Lead Design: The "Gullwing" description means the metal leads bent downward and then outward.

Soldering & Assembly: These leads provide solid footing on the copper pads during assembly. They are ideal for automated pick-and-place and reflow soldering but are also large enough to allow for relatively easy hand soldering.

Package Variants: This package style comes in various standardized sizes to accommodate different thermal requirements and spatial limitations.

Common Applications Include: Smartphones and wearable devices, IoT modules and compact consumer electronics, Power supply circuits and automotive modules, LED lighting drivers and signal conditioning.

  Common Small Outline Diode (SOD)
  Sizes

  Case Code

  Package Dimensions

  SOD-123

  3.68 mm x 1.17 mm x 1.60 mm

  SOD-128

  5.00 mm x 2.70 mm x 1.10 mm

  SOD-323

  1.70 mm x 1.25 mm x 0.95 mm

  SOD-523

  1.25 mm x 0.85 mm x 0.65 mm

  SOD-723

  1.40 mm x 0.60 mm x 0.59 mm

Small Outline Diode Flat Lead (SODFL)

Small Outline Diode Flat Lead (SODFL): A compact, ultra-low-profile surface mount technology (SMT) semiconductor housing designed to replace standard Gullwing SOD packages. By utilizing flat, folded metal ribbons that lie completely flush beneath the bottom of the device rather than curve outward, it maximizes board space, increases power handling, and significantly lowers the component profile.

Core Advantages Over Gullwing Variants:
Space Saving: Eliminating extending Gullwing leads shrinks the necessary circuit board footprint. For example, an SOD-123FL serves as a direct drop-in replacement on existing pads but reduces physical component clearance.
Superior Thermal Performance: Because the flat leads are positioned directly underneath the component body, the heat dissipation path to the PCB copper pads is incredibly short. This design offers up to 25% lower thermal resistance compared to standard packages.
Ultra-Low Profile: These packages typically feature a maximum height profile of just 1.00 mm to 1.20 mm. This represents a profile reduction of 25% or more compared to traditional alternatives, making them ideal for high-density stack-ups.
Increased Surge Capacity: Many flat lead designs incorporate an internal clip-attach structure rather than fragile wire bonds. This structural change boosts transient forward surge-current survival.
Common Applications: The combination of enhanced thermal dissipation and minimized Z-axis height makes SODFL variants highly desirable for: 
Portable Electronics: Ultra-thin smartphones, smartwatches, and portable power banks.
Power Conversion: Secondary rectification and freewheeling diodes in compact AC/DC or DC/DC converters.
Circuit Protection: High-efficiency Schottky rectifiers, Zener voltage stabilizers, and Transient Voltage Suppression (TVS) applications.

Capacitor, Aluminum Electrolytic (CAPAE)

Capacitor, Aluminum Electrolytic (CAPAE): A specialized housing used for components that provide high volumetric capacitance in a relatively compact space. Constructed by winding an anode foil, paper separators saturated with liquid electrolyte, and a cathode foil into a cylinder, these packages are polarized and feature distinct physical markers to indicate the negative terminal.

Unlike monolithic ceramic capacitors, these parts are housed in distinct mechanical form factors dictated by their mounting style, ripple current capability, and spatial constraints.

SMD aluminum electrolytic capacitors are typically packaged in cylindrical metallic aluminum "cans" sitting atop a square, black plastic insulating base. The base bends the terminal leads flat under the component body to create solder pads for reflow soldering. 

Polarity Indicator: A highly visible black or dark colored crescent/stripe painted directly onto the top face of the metallic cylinder denotes the negative pad.

  Common
  Aluminum Electrolytic Capacitor Sizes

  Case Code

  Diameter
  x Height

  Common
  Values

  A

  4.00 mm x 5.40 mm

  1uF to 10uF (50V)

  B

  5.00 mm x 5.40 mm

  10uF to 22uF (35V)

  C

  6.30 mm x 5.40 mm

  47uF to 100uF (16V)

  D

  6.30 mm x 7.70 mm

  100uF to 22uF (25V)

  F

  8.00 mm x 10.20 mm

  220uF to 470uF (35V)

  G

  10.0 mm x 10.20 mm

  470uF to 1000uF (16V)

Crystals (XTAL)

Crystals (XTAL): A specialized, surface mount housing designed for passive timing components. Unlike multi-pin active oscillators that require separate power, a 2-pin crystal package only contains the raw quartz blank and two electrical terminals. It relies entirely on the microcontroller's internal inverter circuit to generate a clock signal. 

Construction and Hermetic Sealing: Because quartz crystals are highly sensitive to moisture, dust, and atmospheric pressure changes, the packages utilize a hermetic (airtight) seal.
The Body: The base is typically constructed from a multi-layer technical ceramic material.
The Lid: A metal seam-welded lid or a glass-sealed ceramic lid covers the top. This metal lid is often grounded internally or externally to shield the sensitive crystal blank from Electromagnetic Interference.
SMD crystal packages are standardized by their physical length and width dimensions. The industry has shifted heavily toward smaller footprints to fit dense modern electronics.

  Common SMD Crystal Packages

  Case Code

  Package Dimensions
  L x W x H Range

  Typical Uses

  5032

  5.0 x 3.2 x 1.0 -1.20 mm

  Microcontrollers

  3225

  3.2 x 2.5 x 0.7 - 0.90 mm

  Ease
  of Routing

  2520

  2.5 x 2.0 x 0.5 - 0.60 mm

  loT Modules

  2016

  2.0 x 1.6 x 0.45 mm

  Smartphones

Side Concave Packages 2-pin

Side Concave Packages: A surface mount electronic component housing where the electrical terminations or leads are recessed into indented, semicircular, or "scalloped" channels along the vertical sidewalls of the component body. Unlike standard convex component packages where leads protrude outward (like Gullwing leads) or flat surfaces, the concave architecture places the solderable terminals inside these inner grooves.

Assembly and Manufacturing Impact
Solder Joint Integrity: Early designs favored concave configurations under the assumption that isolating the paste within the inner channel would mitigate solder bridging. Modern automated optical inspection (AOI) data shows that the absolute spacing on the PCB pad layout dictates bridging protection far more than the concave shape itself.
No-Lead Visual Inspection: Certain modern variations of side concave packages overlap with side-wettable flanks seen in Dual Flat No-Lead (DFN) configurations. This recess allows solder paste to travel upward into the side groove, creating a visible fillet that validates a solid mechanical bond during high-speed assembly inspection.

Dual Flat No-Lead (DFN)

Dual Flat No-Lead (DFN): A surface mount electronic component housing with a near-zero profile that replaces traditional extending leads with flat, metal contact pads on its underside. 

Key Design and Structural Features
Bottom-Surface Pads: Electrical contacts sit flush with the bottom plastic mold compound, eliminating vulnerable, bendable pins.
Thermal Pad: Most DFN packages feature an exposed center metal pad that is soldered directly to the PCB to channel heat away from the silicon die.
Ultra-Low Profile: The compact design minimizes component height and weight, making it ideal for mobile devices and high-density boards.
Performance Advantages
Excellent Thermal Dissipation: The exposed center pad creates a direct thermal highway, allowing high power processing in a tiny footprint.
Low Parasitic Impedance: Eliminating long lead wires reduces internal resistance and inductance, enhancing high-frequency signal performance.
Cost-Efficient: The simplified lead frame design uses less raw material and is highly cost-effective to manufacture at scale.
Assembly and Inspection Challenges
Hidden Solder Joints: Because the connections sit underneath the package, traditional visual inspection cannot verify electrical connectivity or find voids.
Side-Wettable Flanks (SWF): Modern DFN variants feature a specialized cut or plating on the side edge of the pad. This allows solder to wick up the outer wall, creating a visible fillet for Automated Optical Inspection (AOI).
Solder Mask and Stencil Design: Precise stencil opening design is required for the thermal pad to prevent "floating," where excess solder lifts the component and prevents the perimeter signal pads from making contact.