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Advanced Skills Soldering Class
Instructor: Ted Markson
Lecture Goals
Learn about Surface Mount Technology
Become familiar with more-complex soldering techniques
View demonstrations of common SMT procedures
Hands-on assembly with a SMD kit
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Surface Mount Technology
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What is SMT?
Acronym for ‘Surface Mount Technology’
Method for assembling components onto a PCB surface
The leading circuit board assembly practice
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SMT Compared to Thru-hole Technology
Smaller component size, i.e. smaller land pattern
Higher density components, i.e. more connections to the
board
Less solder used in assembly
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SMT Advantages
Smallest and most-dense component packages
Simplified setup for automated assembly
Quick assembly
Automatic physical error correction
Reliably repeatable end-products
Lower cost in general, per unit (components, assembly,
setup, tooling)
Highest performance of end-product
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RF signal effects
Lowered inductance via pin-to-pad connection
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SMT Disadvantages
Difficult single-unit assembly or repair
Difficult QA and inspection
SMDs are prototyping-prohibitive
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SMT Component Packages
Refer to Electronic Industry Alliance for latest specifications
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2-pin Packages
Numeric Outlines
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The component size is a reference to actual dimensions
Generally passive components such as resistors and capacitors
For example, 1206 (3216 metric) is 0.126 x 0.063 in (3.2 x
1.6mm)
Small Outline Diode (SOD)
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For example, SOD-123 is 3.68 x 1.17 x 1.60mm
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Few-pin Packages
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Small Outline Transistors (SOT)
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Usually in 3, 5, or 6-pin packages
Common components are transistors and voltage regulators
For example, SOT-23 is usually 2.9 x 1.3mm
Discrete Packaging (DPAK, D2PAK, D3PAK)
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Common components are voltage regulators and MOSFETS
D2PAK is a common equivalent to TO-220
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Multi-pin Packages, Dual In-line
Acronym
Name
Description
Small-outline Integrated Circuit
8+ pins
Gull-wing lead form
1.27 mm lead pitch
J-leaded Small-outline
Like SOIC with J-leads
TSOP
Thin Small-outline Package
Thinner than SOIC
0.5 mm lead pitch
SSOP
Shrink Small-outline Package
0.635 or 0.8 lead pitch
TSSOP
Thin Shrink Small-outline Package
Lead pitch varies
QSOP
Quarter-size Small-outline Package
0.635 mm lead pitch
VSOP
Very Small Outline Package
0.4, 0.5, or 0.65 mm lead pitch
DFN
Dual Flat No-lead
SOIC
SOJ
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Multi-pin Packages, Quad In-line
Acronym
PLCC
Name
Description
Plastic Leaded Chip Carrier
Square
QFP
Quad Flat Package
LQFP
Low-profile Quad Flat Package
1.4 mm height
PQFP
Plastic Quad Flat-pack
44+ leads
CQFP
Ceramic Quad Flat-pack
MQFP
Metric Quad Flat-pack
Metric lead pitch
TQFP
Thin Quad Flat-pack
Thinner version of PQFP
QFN
Quad Flat No-lead
LCC
Leadless Chip Carrier
Contacts are vertically recessed
MLP
Micro Lead-frame Package
0.5 mm lead pitch, no pins
PQFN
Power Quad Flat No-lead
Exposed die pads for heat-sinking
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Multi-pin Packages, Grid Arrays
Acronym
Name
Description
BGA
Ball Grid Array
Rectangular array of solder
balls, 1.27 mm typical pitch
LGA
Land Grid Array
Mates with on-board socket
FBGA
Fine Pitch Grid Array
Pitch less than 1.27 mm
LFBGA
Low Profile Fine Pitch Ball Grid Array 0.8 mm typical pitch
TFBGA
Thin Fine Pitch Ball Grid Array
0.8 mm typical pitch
Column Grid Array
Rectangular array of solder
cylinders or columns
CCGA
Ceramic Column Grid Array
Ceramic bodied CGA
µBGA
Micro BGA
Ball pitch less than 1 mm
Lead-less Package
0.5 mm typical ball pitch
CGA
LLP
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Soldering Specifics
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SMT Production Assembly Techniques
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Manual Placement
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Human using a soldering station to assemble components
Speed per item is comparable to thru-hole assembly, though
the time per pin is much greater
QA is usually done with automated processes, such as X-ray
examination, Ultrasonic testing, and/or Electrode testing
Automated Placement
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Solder paste is applied via stencil and screen print process
Components placed onto board with pick-and-place machine
Soldering procedure is completed in-batch using Infrared or
Hot gas methods
QA is usually done with automated processes
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Land Patterns
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Used to describe the arrangement of pads on a PCB
While there are package standards, some components
use package variants with different land patterns
Proper patterns can always be found in datasheet or by
contacting manufacturer
Guideline: verify land patterns with component specs if
pattern has not been tested in one month. Pay attention
to easily-varied details: lead pitch and pad size
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Joints
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Good mechanical connection when possible – let the pad
contact the PCB pad before soldering
Clean the pads before placing the component
Proper heat transfer from iron to target: Tip the tip!
Avoid ‘cold’ and ‘mounding’ joints
Mis-aligned components are more common in SMT
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Tack-down multi-pin components
Still be weary of pad stress from
re-heating and lifting PCB pads
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Soldering Techniques - Intro
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Inside to outside
Smallest to largest
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Soldering Techniques - Heat-and-slide
For ‘2-pin’ or ‘few-pin’ packages
1. Use conical tip
2. Clean area with isopropyl alcohol or liquid flux
3. Grab component with tweezers
4. Heat single pad, then slide component into land pattern
5. Remove iron from single pad
6. Verify proper component alignment to land pattern
7. Connect other pads
8. Clean area with alcohol and let dry
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Soldering Techniques - Sweep
For all package types
1. Use hoof, blade, or chisel tip
2. Clean area with isopropyl alcohol or liquid flux
3. Apply flux to target pads
4. Hold component to board with tape or by tacking
5. Melt solder onto tip
6. Slide tip with solder into joint(s), wait for solder flow
into pads, slide tip away
7. Repeat sliding procedure until all pads connected
8. Clean area with alcohol and let dry
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Soldering Techniques - Drag
For all package types
1. Use hoof or conical tip
2. Clean area with isopropyl alcohol or liquid flux
3. Apply flux to target pads
4. Hold component to board with tape or by tacking
5. Melt solder onto tip
6. Drag tip with solder along pads parallel to IC edge, with
sufficient force to allow solder to connect pin and pad
7. Verify heel, side, and toe fillet joints
8. Clean area with alcohol and let dry
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Demonstration
http://www.youtube.com/watch?v=5uiroWBkdFY
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Questions?
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Build Your Kit!
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