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A Complete Study of SMT Components | Component Packages and Types

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Question
Which is a good and reliable circuit with SMT components or with through-hole components?

This article introduces what SMT technology is, the historical origin and development process of SMT, introduces common parts and special parts respectively and finally talks about the assembly technology.

Part 1: Modern Surface-mount Technology (SMT)

Now the majority of PCB assemblies are only available in SMT form.

This is because SMT has a high degree of automation, and the components are quickly transported directly to the assembly machine through the surface mount component reel, which greatly improves production efficiency.

Therefore, under the new assembly technology, the original electronic parts can be fixed on the PCB board better and faster, this will be conducive to large-scale PCB assembly .

How much do you know about SMT components? This blog will take you to learn more about SMT components and packaging methods.

Part 2: Common SMT Components (resistors, capacitors, ICs)

Except for connectors and ports which need mechanical strength and high current components, almost all electronic components are now available in SMT packages.

We will look at some of the common SMT component types and packages we usually come across in PCBs.

1. Resistors

The most common type of component in a PCB is the resistor.

The surface mount device(SMD) package of a resistor comes as a rectangle with leads on both sides or an array of rectangles with multiple resistors.

Resistor.jpg

  • 1.Three figure coding scheme
  • 2.Four figure coding scheme
  • 3.EIA96 coding scheme

Three figure coding scheme

This scheme is normally used for standard tolerance resistors.

The first two figures are multiplied by the base ten power of the third figure to get the resistance value.

For resistor values under 10, the ‘R’ letter is used to indicate the decimal point.

three figure.jpg

Four figure coding scheme

This is much similar to the three-figure scheme but has 3 figures and one multiplier figure.

This scheme is used for higher tolerance resistors. For resistor values under 100, the ‘R’ letter is used to indicate the decimal point.

four figure.jpg

EIA96 coding scheme

This scheme also has three figures but aims to cover high tolerance resistors.

It consists of two numbers and one letter which is the multiplier.

But the significant value and multiplier are not straightforward and to read values you need to refer to the standard EIA96 table.

Code
Multiplier
Z
0.001
Y or R
0.01
X or S
0.1
A
1
B or H
10
C
100
D
1000
E
10000
F
10000
100000
10000

Capacitors

There are two main types of capacitors. Which are polar and non-polar.

Polar surface mount capacitors have polarity and capacity markings on the top side and have a common cylindrical capacitor shape.

capacitors.jpg

Most SMD capacitors you would encounter would not have any markings on them.

For example 10uf 0805 ceramic capacitor (middle one)

3. Integrated Circuits (ICs)

The bulk of the surface mount devices are ICs, and they got the largest variety of packages.

The following chart demonstrates most of the surface IC varieties with examples.


Material
Type
Image
Symbol
Lead count
Plastic

SOP

(Small Outline Package)

 

  SOP.jpg

MAzxcsdfsdfdsf

8, 16

Plastic

SSOP

(Shrink Small Outline Package)

SSOP.jpg 

MB

20, 30, 32, 60, 64, 70

Plastic

TSOP

(Thin Small Outline Package)

TSOP.jpg 

TA

20,24,26,28,

32,40,44,48,

50,54,66,64,

70,86

Plastic

QFP

(Quad Flat Pack)

QFP.jpg 

GA

44, 56, 64, 80,

100, 128, 160,208,

240,272,304

Plastic

TQFP

(Thin Quad Flat Pack)

TQFP.jpg

TB

44, 48, 64, 80,

100, 120

Plastic

LQFP

(Low-profile Quad Flat Package)

LQFP.jpg 

TC
144, 176, 208
Plastic

SOJ

(Small Outline J-lead)

SOJ.jpg 

JA

20, 24, 26, 28,

32, 36, 40, 42, 50

Plastic

QFJ

(Quad Flat J-leaded) /

PLCC

 (Plastic Leaded Chip Carrier)

QFJ.jpg 

JB

18, 29, 22, 28,

32, 44, 68, 84

Plastic

BGA

(Ball Grid Array)

/

FBGA

(Fine Pitch Ball Grid Array)

BGA.jpg 

LA

48, 84, 104, 144,

176, 224, 256, 352,

420, 560

Plastic

FLGA

(Fine Pitch Land Grid Array)

FLGA.jpg 

LB
49, 56, 84, Custom designs

Plastic

W - CSP

(Wafer Level Chip Scale Package)

W- CSP.jpg 

FB

208, 256

Plastic

HQFP

(Heat sunk Quad Flat Pack)

HQFP1.jpg 

FB

208, 256

Part3: Special SMT Components

Other than the above discussed there are surface mount devices and components which are custom designed and uncommon to find.

Some of them are listed below.


Type
Image
Symbol
Lead count
COB (Chip On Board)

COB.jpg

KA
Custom
TCP (Tape Ca)

TCP.jpg

VA
Custom
COT (Chip On Tape)

COT1.jpg

KC
IC Card


COB (Chip on Board)

In this custom design, the IC is mounted directly on the printed board and sealed by a plastic cover.

Usually, there are no specifications written on the cover.

Commonly used in custom low-cost products like toys, the chip is not removable.

TCP (Tape Carrier Package)

These are produced by Tape Automated Bonding (TAB).

These are suitable for high-density multi thin pin applications.

COT (Chip on Tape)

A microchip is directly mounted and sealed on a substrate.

A common use is SIM cards, ID cards, and bank cards.

Part 4: SMT Component Packages

Almost all SMT package types that exist today aim to ease assembly automation.

Modern PCB manufacturing chooses ratios between SMT to through-hole (TH) to achieve space-saving of 50 to 90 percent.

This paved path for electronic appliances to get smaller and pack more features.

Currently, there are dozens of SMT package types.

One of the main reasons for the diversity of SMT packages is the number of functions or I/Os per device (integrated circuit) has increased, besides, accommodating these ICs will increase I/O count and reduce contact pitch.

For Example: Fine pitch (0.5mm) and Ultra Fine Pitch (0.4mm - 0.3mm).

Over 50% of all SMT components in the market have an I/O count in the 16–64 I/O range, and only 5-10% contains an I/O count over 200.

Many of the high I/O count devices have area array packaging formats such as ball grid arrays (BGAs).

The heart of the surface mount technology is the machine that precisely places SMT components onto the printed board prior to soldering.

Surface mount placement machines are more advanced than through-hall (TH) insertion machines and usually capable of handling different SMT component types simultaneously.

The following two tables show the relationship of SMT component package I/O count to the pitch considering the main two variations.

The first number in the matrix cell reflects the design complexity and the second number reflects the difficulty of the manufacturing process.

components package 1.jpg

      component package 2.jpg

To have a general understanding of SMT components and packaging we can refer to IPC National Technology Roadmap for Electronic Interconnections, which published the following overall classification.


Class A

Through -hall(TH) components only

Class B

Surface mount devices (SMD) only

Class C

A mixture of Through-hole(TH) and simplistic SMD

Class X

The complex intermix of Through -hall(TH), simplistic SMD, fine pitch (FP), and ball grid array (BGA)

Class Y

The complex intermix of Through -hall(TH), simplistic SMD, Ultrafine pitch (UFP), and chip-scale package(CSP)

Class Z

The complex intermix of Through -hall(TH), simplistic SMD, Ultrafine pitch (UFP), Chip On Board (COB), Flip Chip (FC), and Tape carrier package(TCP)

Part 5: How to Find a Relieved PCB Components Assembler?

PCBONLINE is a factory connected online store of the Global Success Group. Providing high-end EMS (electronics manufacturing service), including but not limited to advanced PCB manufacturing, assembly, layout service, and component sourcing. Aiming to always provide the best PCBs/PCBA and EMS service to simplify your electronic production. About SMT, PCBONLINE has rich experience in the whole SMT process including but not limited to SMT stencil design and manufacturing. SMT enables fast, precise, and cost-effective assembling. PCBONLINE, a PCB manufacturer, knows how to design and manufacture your stencils to be best, and also provide suggestion in PCB assembly for free.

Conclusion

Components assembly requires extreme Accuracy and stability. If you have read the whole article you should now be aware of rough SMT components.

PCBONLINE   provides the best PCB assembly with efficient SMT equipment and professional Assembly personnel. Any type of order or amount is available for assembly if you get in touch with PCBONLNE. If you have any hesitation, you can click to get a quote online free of charge.


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