SMT Components: The Beginner’s Guide

Pcbandassembly deals with numerous components suitable for surface mount technology (SMT) when manufacturing or assembling PCBs for customers. This is because almost all electronic products we mass-produce today use SMT components due to their multiple advantages.

1. SMT Component Division

Component manufacturers offer SMT components in a variety of packages and standardize the packages so that assemblers can easily use them in automated equipment. SMT components can be divided into two major categories: passive components and active components.

While passive components mostly come in small rectangular packages, some also have cylindrical packages. Although passive SMT components have the most variety, it really depends on the level of interconnect required, the technology used by the manufacturer, and many other factors. However, there are two main factors that determine the type of package a manufacturer uses for SMT components:

• Processing

• Standard

1) SMT Packaging Processing

SMT packages have been developed with component handling in mind. 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 the reduction of manufacturing costs while making sure that the 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 tape to hold the components in a line, while a second tape sticks loosely onto the back to retain the components. The pick-and-place machine removes the holding tape as it picks up the component, exposing the next component to be used.

Larger components, such as dual in-line surface mount ICs, are usually packaged in tubes, and the machine removes them one by one from the tube as needed. Gravity forces the next IC to slide off the tube, ready for the next pick.

Larger ICs such as flat packages, QFPs, BGAs, etc. may come in tray or waffle packages. The pick-and-place machine can handle these packages and remove them for mounting as needed.

2) SMT Packaging Standards

Standards provide a great deal of consistency across the industry. Most SMT components are sized to industry standards, such as the JEDEC specification. Although different types of components require different SMT packages, the fact that they conform to standards keeps the design of printed circuit boards simple, as designers can use standard outlines and pad sizes.

In addition, SMT components in standard-sized packages simplify manufacturing for placement machines, which can use standard feedstock to process the components, thus reducing costs. Standards categorize different SMT packages based on component type while retaining standard footprints for each, such as:

• Passive rectangular components

• Tantalum capacitors

• Electrolytic capacitors

• Transistors and diodes

• DIL integrated circuits

• QIL integrated circuits

• Chip-on-board ICS

2. SMT Component Types

1) Passive Rectangular Components

SMT groups mainly include passive resistors, capacitors, and inductors. Technological advances have made it possible to manufacture and use components of increasingly smaller sizes.

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.

2) Tantalum Capacitors

The construction of SMT type tantalum capacitors is different, forcing manufacturers to make them in different sizes than those listed above. The most common tantalum capacitor sizes are:

3) Electrolytic Capacitors

Electrolytic capacitors come in large varieties depending on their capacitance value and their working voltage. The most common sizes are:

4) Transistors & Diodes

Manufacturers offer transistors and diodes in the same type of SMT packages. Although diodes only have two terminals, it is easier to place packages with three terminals. Although manufacturers offer a wide variety of SMT transistors and diodes, the most popular ones are:

5) DIL Integrated Circuit Packaging

There are many types of DIL ICs available from manufacturers, the most common of which are:

6) QIL Integrated Circuit Packaging

These are common flat package type ICs for surface mounting. Of the several variations available, the most common are:

√ QFP: This is the most common type of flat package and has many variations like LQFP, PQFP, CQFP, TQFP etc. The pins come out from all four sides and can be either gull-wing or J-type leads.

√ PGA: Pin Grid Array packages are usually square with pins coming out of the bottom. The pins may or may not cover the entire bottom surface. Variants include flip chips, staggered pins, and ceramic types. PGA packages offer more interconnects than QFP.

√ BGA: Ball Grid Array is similar to PGA, with solder balls instead of pins, making BGA more robust. BGA provides very high-density interconnects, lower thermal resistance between PCB and package, and very low inductance on the leads, enabling high-speed and high-frequency operation.

3. Summary

Billions of SMT components are used across the industry. However, before a package can be used on a circuit board, the OEM must ensure that its contract manufacturer has the right pick and place machine to handle it. Pcbandassembly has the latest and most advanced machines for all types of PCB assembly. For any type of PCB manufacturing and assembly using SMT components, contact Pcbandassembly today.