SMT Components
Rush PCB handles a large variety of components suitable for Surface Mount Technology (SMT) while designing and/or assembling PCBs for our customers. This is because almost all the electronics we mass-produce today use SMT components, as they offer several advantages.
Component manufacturers offer SMT components in many packages, and they standardize the packages so that assemblers can use them easily in automated equipment. One can segregate SMT components into two broad categories—passive components and active components.
While passive components are mostly in small rectangular packages, some are available in cylindrical shapes as well. Although the maximum variety is inactive SMT components, it really depends upon the level of inter-connectivity required, the technology the manufacturer uses, and a host of other factors. However, two major factors govern the variety of packages that manufacturers use for SMT components:
- Handling
- Standards
SMT Package Handling
Development of SMT packages had proceeded with considerations for component handling. SMT technology aims primarily to facilitate automated PCB assembly. Hence, manufacturers place special attention on to the design of packages that make it easy for Pick-and-place machines to handle them easily during the assembly of printed circuit boards.
Allowing easy component handling ensures reduction of manufacturing costs, while making sure that quality of final equipment is high, resulting in the highest quality for the assembled PCBs. Ease of handling often allows holding small components loosely in a hopper, feeding them down a tube, and allowing the machine to pick them out as necessary while mounting.
Other larger SMT components, both active and passive, such as resistors, capacitors, diodes, and transistors are available in tapes on reels. The reel usually has a tape to hold the components in a line, while a second tape sticks loosely onto the back for retaining the components. The pick-and-place machine pulls off the retention tape as it picks the component, thereby exposing the next component it will use.
Bigger components such as dual-in-line surface mount ICs often come in tubes, and the machine removes them individually from the tube as necessary. Under gravity, the next IC slides down the tube, ready for pick up next.
Still larger ICs, such as flat packs, QFPs, BGAs, may come in trays or waffle packs. Pick and place machines can handle such packs, removing them as necessary for mounting.
SMT Package Standards
Standards offer a large degree of conformity across the industry. Sizes of most SMT components conform to industry standards such as JEDEC specifications. Although different types of components require different SMT packages, the fact that they conform to a standard allows the design of printed circuit boards to remain simply, as designers can use standard outlines and pad sizes.
Furthermore, the availability of SMT components in standard size packages simplifies the manufacturing of pick-and-place machines, which can use standard feed for the components, thereby reducing costs. The standards categorize different SMT packages based on the type of the component while maintaining standard packages for each, such as:
- Passive Rectangular Components
- Tantalum Capacitors
- Electrolytic Capacitors
- Transistor & Diodes
- DIL Integrated Circuits
- QIL Integrated Circuits
- Chip on Board ICS
Passive Rectangular Components
This SMT group mainly comprises passive resistors, capacitors, and inductors. Technological progress is allowing the manufacture and use of increasingly smaller size components.
| Passive SMD Package Type | Dimension (inches) | Dimension (mm) |
| 2920 | 0.29 x 0.20 | 7.4 x 5.1 |
| 2725 | 0.27 x 0.25 | 6.9 x 6.3 |
| 2512 | 0.25 x 0.125 | 6.3 x 3.2 |
| 2010 | 0.2 x 0.1 | 5.0 x 2.5 |
| 1825 | 0.18 x 0.25 | 4.5 x 6.4 |
| 1812 | 0.18 x 0.125 | 4.6 x 3.0 |
| 1806 | 0.18 x 0.06 | 4.5 x 1.6 |
| 1210 | 0.125 x 0.10 | 3.2 x 2.5 |
| 1206 | 0.12 x 0.06 | 3.0 x 1.5 |
| 1008 | 0.10 x 0.08 | 2.5 x 2.0 |
| 0805 | 0.08 x 0.05 | 2.0 x 1.3 |
| 0603 | 0.06 x 0.03 | 1.5 x 0.8 |
| 0402 | 0.04 x 0.02 | 1.0 x 0.5 |
| 0201 | 0.02 x 0.01 | 0.6 x 0.3 |
| 01005 | 0.016 x 0.008 | 0.4 x 0.2 |
Of the sizes shown above, 0402 and 0603 are the most popular SMD sizes that designers and assemblers use. The 1206 and 1812 sizes are mostly for specialized components requiring higher levels of power dissipation. However, the industry is increasingly moving towards more miniature forms such as 0201 and 01005. Usually, SMD inductors are available in 0603 and 0805 sizes.
Tantalum Capacitors
Tantalum capacitors of the SMT type have a different construction, forcing manufacturers to make them in sized different to those listed above. Most common tantalum capacitor sizes are:
| Common SMD Tantalum Capacitor Packages | |||
| SMD Package Size | EIA Standard | Dim. (Inches) | Dim. (mm) |
| A | EIA 3216-18 | 0.13 x 0.06 x 0.06 | 3.2 x 1.6 x 1.6 |
| B | EIA 3258-21 | 0.14 x 0.11 x 0.075 | 3.5 x 2.8 x 1.9 |
| C | EIA 6032-20 | 0.24 x 0.13 x 0.87 | 6.0 x 3.2 x 2.2 |
| D | EIA 7343-31 | 0.3 x 0.17 x 0.1 | 7.3 x 4.3 x 2.4 |
| E | EIA 7343-43 | 0.3 x 0.17 x 0.16 | 7.3 x 4.3 x 4.1 |
Electrolytic Capacitors
Electrolytic capacitors come in large varieties depending on their capacitance value and their working voltage. The most common sizes are:
| Common SMD Electrolytic Capacitor Packages | ||
| SMD Package Type (Panasonic) | Dimensions (inches) | Dimensions (mm) |
| A | 0.13 x 0.13 | 3.3 x 3.3 |
| B | 0.17 x 0.17 | 4.3 x 4.3 |
| C | 0.2 x 0.2 | 5.3 x 5.3 |
| D | 0.26 x 0.26 | 6.6 x 6.6 |
| E/F | 0.33 x 0.33 | 8.3 x 8.3 |
| G | 0.4 x 0.4 | 10.3 x 10.3 |
| H | 0.53 x 0.53 | 13.5 x 13.5 |
| J | 0.67 x 0.67 | 17.0 x 17.0 |
| K | 0.75 x 0.75 | 19.0 x 19.0 |
Transistors & Diodes
Manufacturers offer transistors and diodes in the same type of SMT packages. Although diodes have only two terminals, it is easier to place packages having three. While a large variety of SMT transistors and diodes are available from manufacturers, the most popular among them are:
| Common SMD Transistor and Diode Packages | |||
| SMD Package Type | Used for | Dim. (inches) | Dim. (mm) |
| SOT-23 | Small Signal Diodes, Transistors, ICs (Op-Amps etc.) | 0.12 x 0.07 x 0.05 | 3.0 x 1.75 x 1.3 |
| SOT-223 | Medium Power Diodes and Transistors | 0.26 x 0.15 x 0.07 | 6.7 x 3.7 x 1.8 |
| DPAK | High Power Diodes and Transistors | 0.25 x 0.09 x 0.4 | 6.5 x 2.25 x 10.2 |
DIL Integrated Circuit Packages
Manufacturers offer a large variety of DIL IC Types, and the most common among them are:
Common DIL Integrated IC Packages |
|||
| SMD Package Type | Pin Type | Pin Spacing (mils) | Pin Spacing (mm) |
| SOIC | Gull-Wing | 50 | 1.27 |
| SSOP | Gull-Wing | 25 | 0.635 |
| TSSOP | Gull-Wing | 25.6 | 0.65 |
| SOJ | J-leaded | 50 | 1.27 |
QIL Integrated Circuit Packages
These are the generic flat package type ICs for surface mount. Among the several variants available, the most common are:
QFP: This is the most generic type of flat package with several variants such as—LQFP, PQFP, CQFP, TQFP, and more. Pins exit from all four sides, and they may be gull-wing or J-leaded.
PGA: Pin Grid Array packages are usually square with pins exiting from the underside. The pins may or may not cover the entire bottom surface. Variants include Flip-Chip, Staggered pin, and Ceramic types. Compared to QFP, PGA packages offer substantially more interconnections.
BGA: Ball Grid Arrays are like PGAs, with solder balls replacing the pins, making BGAs sturdier. BGAs offer very high-density interconnections, lower thermal resistance between the PCB and the package, and very low inductance on leads enabling high-speed and high-frequency operation.
Conclusion
The industry uses SMT components by the billions. However, before using a package for their boards, OEMs must ensure their contract manufacturer has the proper pick and place machine to handle it. Rush PCB has the latest and state-of-the-art machinery for all types of PCB assembly. For any type of PCB design and assembly using SMT components contact Rush PCB today.