ECE Projects LabECE Projects Lab

Surface Mount TechnologySurface Mount Technology

What is SMT?What is SMT?

Surface Mount TechnologySurface Mount Technology

Used primarily in industryUsed primarily in industry

Same circuitry with much smaller Same circuitry with much smaller componentscomponents

Was not intended for individual soldering, Was not intended for individual soldering, but gaining popularitybut gaining popularity

SMT ComponentsSMT Components

““Reflow”Reflow”a thermal process in which solder paste is a thermal process in which solder paste is used to electrically connect components to used to electrically connect components to their attachment pads. It is the most their attachment pads. It is the most common means to attach a surface common means to attach a surface mounted component to a circuit boardmounted component to a circuit board

““Reflow temperature” is the temperature at Reflow temperature” is the temperature at which the solder paste changes state from which the solder paste changes state from solid to liquidsolid to liquid

SMT BoardSMT Board

Why SMT (advantages)?Why SMT (advantages)?

Much smaller sizeMuch smaller size

Components on both sides of boardComponents on both sides of board

Leads can be much shorter reducing Leads can be much shorter reducing inductance and resistance thereby inductance and resistance thereby increasing performanceincreasing performance

Prototyping is more indicative of the final Prototyping is more indicative of the final productproduct

How to SMT solder (techniques)How to SMT solder (techniques)

Fine tip solderingFine tip soldering– Uses conventional soldering techniques on a Uses conventional soldering techniques on a

much smaller scalemuch smaller scale

Hot plate reflowHot plate reflow– Useful for single ICs with limited footprintUseful for single ICs with limited footprint

Oven reflowOven reflow– Uses soldering paste and reflows entire boardUses soldering paste and reflows entire board

How to SMT reworkHow to SMT rework

Solder wickSolder wick– Uses fine mesh conductive Copper braid. Uses fine mesh conductive Copper braid.

Heat and capillary action pulls excess solder Heat and capillary action pulls excess solder awayaway

Hot air reflowHot air reflow– Uses hot air to reflow the solder with Uses hot air to reflow the solder with

components presentcomponents present

De-Solder vacuum plunger/suckerDe-Solder vacuum plunger/sucker– Uses small negative pressure to suck up Uses small negative pressure to suck up

excess solderexcess solder

Fine Tip SolderingFine Tip SolderingConventional EquipmentConventional Equipment

Useful for Larger Useful for Larger componentscomponents

Causes eye strainCauses eye strain

Requires a steady Requires a steady handhand

Fine Tip SolderingFine Tip SolderingSpecialized Fine-tip toolsSpecialized Fine-tip tools

Hot-Air Rework Hot-Air Rework Station AM6500 by Station AM6500 by JBCJBC– Fine tip solder toolsFine tip solder tools– Desoldering toolsDesoldering tools– Hot tweezersHot tweezers– Hot air gunHot air gun

Hot plate reflowHot plate reflow

useful for smaller useful for smaller boards as heat boards as heat distribution on a distribution on a hotplate is far less hotplate is far less uniform than a uniform than a convection ovenconvection oven

end point is end point is monitored visuallymonitored visually

Oven reflowOven reflow

Typical Reflow ovenTypical Reflow oven– Large and bulkyLarge and bulky– Expensive $$$ Expensive $$$

Cuisinart TOB 165– Just as good– A small fraction of the

cost

Oven Reflow OverviewOven Reflow Overview

After applying solder After applying solder paste and setting paste and setting components, the components, the board is inserted to board is inserted to be “cooked”be “cooked”

End result is a End result is a perfectly soldered perfectly soldered board for a fraction of board for a fraction of the cost (no eye strain the cost (no eye strain either)either)

Reflow ProfileReflow Profile

The temperature of The temperature of the reflow process the reflow process must:must:– be precise enough to be precise enough to

not damage IC’s not damage IC’s through excess heatthrough excess heat

– be sufficient for reflow be sufficient for reflow of solderof solder

Oven Reflow StepsOven Reflow Steps Apply soldering pasteApply soldering paste Set IC’s and componentsSet IC’s and components

Cook!Cook! Touch up (here using solder wick)Touch up (here using solder wick)

Industrial SMT MovieIndustrial SMT Movie

Silicon Run IISilicon Run II

Copper Solder Wick (rework)Copper Solder Wick (rework)

useful for removing useful for removing excess solderexcess solder

braided copper mesh is braided copper mesh is used to remove solder used to remove solder via capillary actionvia capillary action

Fine-tip or conventional Fine-tip or conventional soldering iron is used for soldering iron is used for heating braid and solderheating braid and solder

Hot air reflow (rework)Hot air reflow (rework)

Hot-Air Rework Hot-Air Rework Station AM6500 by Station AM6500 by JBCJBC– Fine tip solder toolsFine tip solder tools– Desoldering toolsDesoldering tools– Hot tweezersHot tweezers– Hot air gunHot air gun

How hot air reflow worksHow hot air reflow works

Hot air used to Hot air used to desolder ICdesolder IC

Vacuum extractor Vacuum extractor pulls IC after solder pulls IC after solder flowsflows

De-Solder vacuum plunger/suckerDe-Solder vacuum plunger/sucker(rework)(rework)

Uses small vacuum Uses small vacuum to pull solder away to pull solder away from boardfrom boardHand-held manual Hand-held manual versionversionHeated tip & Heated tip & vacuum combined vacuum combined on SMT rework on SMT rework stationstation

SummarySummary

Fine tip soldering is hard, but essential Fine tip soldering is hard, but essential sometimessometimes

Hotplate or Oven reflow are great for Hotplate or Oven reflow are great for creating a whole board at oncecreating a whole board at once

Rework techniques include Copper wick, Rework techniques include Copper wick, Hot-air reflow, and de-solder vacuumingHot-air reflow, and de-solder vacuuming

ECE Projects Lab can do it allECE Projects Lab can do it all

Credits/Work citedCredits/Work cited

http://en.wikipedia.org/wiki/Surface-mount_technologyhttp://en.wikipedia.org/wiki/Surface-mount_technology– General SMT infoGeneral SMT info

http://www.heinc.com/jbc/repair.htmlhttp://www.heinc.com/jbc/repair.html– Hot air reflow station websiteHot air reflow station website

http://www.bidservice.com/Browses/http://www.bidservice.com/Browses/NF_Detailed_Item_View_new.asp?ProductID=20069NF_Detailed_Item_View_new.asp?ProductID=20069– Place to purchase typical reflow ovenPlace to purchase typical reflow oven

http://www.seattlerobotics.org/encoder/200006/oven_art.htmhttp://www.seattlerobotics.org/encoder/200006/oven_art.htm– Another group that has done a similar project with a toaster ovenAnother group that has done a similar project with a toaster oven

http://www.circuitcellar.com/library/print/0704/Lacoste_168/http://www.circuitcellar.com/library/print/0704/Lacoste_168/– Thermal profile for a toaster ovenThermal profile for a toaster oven

Design Lab WebsiteDesign Lab Website

Presentations availablePresentations available

Online Reflow TutorialOnline Reflow Tutorial

http://www.ee.duke.edu/DesignLab/http://www.ee.duke.edu/DesignLab/

Thanks!Thanks!