Detailed explanation of IC packaging size for voltage regulator chips: key considerations for selection and application
In electronic circuit design, voltage regulator chips (such as LDO linear regulators, DC-DC switching regulators, etc.) are the core components that provide stable voltage. The choice of packaging size is crucial, directly affecting the layout, heat dissipation capacity, assembly cost, final product volume, and performance of the circuit board. Understanding various packaging types and their size characteristics is the foundation for efficient and reliable design.
1、 Why is packaging size important?
Board Space: It directly determines the PCB layout density, especially for portable devices with limited space (such as mobile phones and wearable devices).
Thermal Performance: The packaging size and structure (especially the design of heat dissipation pads/pins) determine the efficiency of heat conduction from the chip to the PCB and the environment. The higher the power of the voltage regulator, the higher the requirements for heat dissipation, usually requiring larger packaging or special heat dissipation design.
Assembly Process: The packaging size and pin spacing affect the accuracy requirements, soldering yield (especially manual soldering), and ease of repair of surface mount machines (SMT).
Electrical Performance: The parasitic inductance/resistance of certain packages (such as lead frame types) may be slightly higher than advanced wafer level packages, which can have a subtle impact on the efficiency or noise of high-frequency, high current applications.
Cost: Typically (non absolute), smaller and more advanced packaging may have higher costs, but the saved PCB space may also lower overall costs. During mass production, there is a significant difference in packaging costs.
2、 Common types and size characteristics of voltage regulator chip packaging
There are many types of voltage regulator chip packaging. The following introduces the mainstream types and their typical size ranges according to "size from small to large" and "popularity" (note: specific sizes vary greatly depending on the manufacturer and specific model, be sure to refer to the data manual!):
SOT (Small Outline Transistor) Series - Ultra Small Lead Frame Packaging
Representative models: SOT-23, SOT-23-5, SOT-89, SOT-223, SOT-323, SOT-563, etc.
Size characteristics:
Extremely small: It is the most widely used ultra small power regulator package.
SOT-23 (3 pins): Typical dimensions are approximately 3.0mm x 1.7mm x 1.3mm (length x width x height). The pin spacing is about 0.95mm.
SOT-23-5 (5-pin): The size is similar to SOT-23, slightly longer or wider.
SOT-89: Slightly larger, with a metal heat sink at the bottom (usually the middle pin), with typical dimensions of approximately 4.5mm x 4.0mm x 1.5mm. The heat dissipation capability is superior to SOT-23.
SOT-223: More emphasis on heat dissipation, with larger back metal heat dissipation pads (Tab), typically measuring about 6.5mm x 7.0mm x 1.8mm. The pin spacing is usually 2.3mm. It is commonly used for medium current (several hundred mA to 1A) LDOs.
SOT-323/563: Smaller than SOT-23, used in extremely limited space situations (such as inside mobile phones).
Applications: Extremely low-power devices, portable devices, space sensitive areas, signal chain power supply, etc. SOT-89/223 is suitable for slightly higher power LDOs.
DFN (Dual Flat No led)/QFN (Quad Flat No led) - Leadless Flat Packaging
Representative models: DFN (such as 3x3, 2x2), QFN (such as 4x4, 5x5, 6x6), etc. The number usually represents the side length of the package (mm).
Size characteristics:
The main force of miniaturization: currently one of the most mainstream packaging types, with compact size and low height.
Pin free: The electrodes and heat dissipation pads are located at the bottom of the package and are directly soldered to the PCB. The significant feature is the large area of thermal pads/exposed pads at the bottom, which greatly improves the heat dissipation efficiency.
Wide size range: DFN sizes can be as small as 1.0mm x 1.0mm or even smaller (WLCSP). Common sizes of voltage regulators include 2mm x 2mm, 3mm x 3mm, 4mm x 4mm, and 5mm x 5mm. The number of pins varies from a few to dozens (QFN).
Pin spacing: usually 0.5mm or 0.65mm, but there are also smaller spacing such as 0.4mm (which requires high SMT process requirements).
Application: Widely used in various low to medium power regulators (LDO and DC-DC), especially in scenarios that require good heat dissipation and compact size. From consumer electronics to industrial equipment, it is ubiquitous.
LGA (Land Grid Array) - Solder Pad Grid Array
Size characteristics:
Similar to QFN, the pinless package also features a pad array at the bottom.
The main difference is that the solder pads are arranged in a grid pattern, not limited to the four sides (QFN's Quad refers to the four sides). But many manufacturers have blurred the naming boundaries between QFN and LGA, and those with heat dissipation pads at the bottom and I/O pads around them are often called QFN.
The size range overlaps with the QFN height (such as 3x3, 4x4, 5x5, etc.).
Application: Similar to QFN, it is commonly used in voltage stabilizing chips with high space and heat dissipation requirements.
WLCSP (Wafer Level Chip Scale Package) - Wafer Level Chip Scale Package
Size characteristics:
Minimum size: The package size is almost equal to the size of a die on chip (DIE) and is currently the smallest size in commercial packaging.
Ultra thin: extremely low height.
Bottom solder balls: directly connected to the PCB through solder balls (Bumps), with very small solder ball spacing (such as 0.4mm, 0.35mm).
Typical sizes can be as small as 1.0mm x 1.0mm or smaller.
Application: Applications with extremely demanding space requirements, such as high-end smartphones, TWS earphones, micro sensor modules, and other internal ultra-low power regulators. The requirements for PCB design and SMT technology are extremely high.
BGA (Ball Grid Array) - Ball Grid Array Package
Size characteristics:
The bottom is a complete tin ball array.
Although the size can be made relatively compact (relative to the number of pins), it is usually slightly larger than QFN/LGA with the same number of pins, and the height is higher (due to the presence of solder balls).
It is not as common in complex ICs such as CPU/FPGA as in voltage regulator chips. Mainly used for PMIC (Power Management Integrated Circuit) with high integration and a large number of pins, or complex multi output DC-DC controllers.
Application: High performance processors, PMIC for FPGA, server power management, and other scenarios that require high integration and multi-channel power supply.
TO (Transistor Outline) series - through-hole/surface mount power type packaging
Representative models: TO-220 (through-hole/surface mount), TO-263 (D ² PAK, surface mount), TO-252 (DPAK, surface mount).
Size characteristics:
Large size, high power: designed specifically for medium to high power, with heat dissipation capability as the core.
TO-252 (DPAK): Surface mount, with large metal fins exposed (Tab), typical dimensions of approximately 6.5mm x 10mm x 2.3mm. Commonly used in DC-DC or LDO with several A currents (requiring good heat dissipation).
TO-263 (D ² PAK): Larger than DPAK, with stronger heat dissipation capability, typical dimensions of approximately 10mm x 15mm x 4.4mm. Can handle larger currents (such as 5A, 10A or even higher).
TO-220: Traditional through-hole packaging (also available in surface mount variants) with metal mounting holes and heat sinks. It has a large volume (typical dimensions are about 10mm x 15mm x 4.5mm, excluding pins) and the best heat dissipation (external heat sinks can be added), but it occupies a large PCB area and requires additional drilling.
Application: Voltage regulators that need to handle high currents (>1A), such as motherboard CPU/GPU power supply, industrial equipment power supply, LED drivers, adapters, etc.
3、 Interpretation and acquisition of packaging size information
The datasheet is the only authoritative source: any third-party information or "typical size" is unreliable. It is necessary to consult the official data manual for the specific model.
Key dimensional parameters:
Mechanical Drawing/Package Outline: includes detailed top view, side view, pin dimensions, tolerances, heat dissipation pad size and position, etc.
Body Size: Length (L), Width (W), Height/Thickness (H).
Pin pitch/solder ball pitch: The distance between the centers of adjacent pins (e.g. 0.5mm, 0.65mm). It is crucial for soldering and PCB wiring.
Thermal Pad/Exposed Pad Size: It is crucial for DFN/QFN/LGA and determines the heat dissipation and soldering area.
Lead Width/All Diameter: Affects current carrying capacity and welding reliability.
Standard packaging codes: such as "SOT-23-5", "DFN-8 (3x3)", "QFN-16 (4x4)", "TO-263-5 (D ² PAK-5)". These codes provide the package type, number of pins, and approximate size range, but the exact size still needs to be determined in the manual.
4、 How to choose the appropriate packaging size?
Choosing encapsulation is a trade off process that requires comprehensive consideration of:
Output power/current: The higher the power, the more heat is generated, requiring a package with stronger heat dissipation capabilities (larger size, with heat dissipation pads/fins). SOT is optional for low current (<100mA); Medium current (several hundred mA-1A) options include SOT-223 and small-sized DFN/QFN; For high currents (>1A), DFN/QFN or TO series with heat dissipation pads must be selected.
PCB space limitation: The tighter the equipment space, the more it requires miniaturization packaging (SOT, small-sized DFN/QFN, WLCSP).
Heat dissipation conditions:
Is there sufficient PCB copper foil area (especially for connecting heat dissipation pads) to dissipate heat?
Is there any airflow? Is the equipment sealed?
Poor heat dissipation conditions require larger or better heat dissipation design packaging.
Assembly capability:
Can the precision of SMT equipment in the factory handle small pitch (such as 0.4mm) packaging?
Do you need manual welding or repair? The manual soldering and maintenance of small-sized packages (DFN/QFN) with heat dissipation pads at the bottom are difficult.
Cost: Choose cost-effective packaging while meeting demand. The cost of standard packaging (such as SOT, common size QFN) is usually lower.
Electrical noise requirements: For applications that are extremely sensitive to noise, sometimes parasitic parameters of the packaging need to be considered (although usually have a small impact).
The packaging size of a voltage regulator chip is the core manifestation of its physical characteristics, which profoundly affects the space, heat dissipation, cost, and reliability of circuit design. From miniature SOT/WLCSP to powerful TO series, each package has its applicable scenarios. There is no 'best' packaging, only the 'most suitable' packaging. Design engineers must:
Clear requirements: A clear understanding of the project's power, space, heat dissipation, cost, and process limitations.
Refer to the manual: strictly follow the data manual of the target chip model to obtain accurate packaging dimensions and mechanical information.
Weigh the pros and cons: Find the best balance point among various constraints.
By gaining a deeper understanding of the significance of packaging size and the characteristics of various types of packaging, engineers can confidently choose the most suitable "outer layer" for voltage regulator chips and even the entire electronic system, thereby designing more compact, efficient, and reliable electronic products.