REFLOW基本知識(shí)課件

Reflow基本知識(shí)REFLOW基本知識(shí)

回流焊的定義回流焊的設(shè)備P150簡(jiǎn)介做溫度曲線步驟熱電偶原理如何放板進(jìn)爐中回流焊造成的缺陷

目錄REFLOW基本知識(shí)

What

isReflow?AprocessthatmeltsthesolderpasteandmakessolderjointsbetweencomponentleadsandcopperpadsonPCB.什么是回流焊？回流焊就是將焊錫溶化并在元件引腳與線路板上的焊盤之間形成美觀、可靠聯(lián)接的工藝過(guò)程元件(Component)焊膏(SolderPaste)印刷線路板(PCB)ReflowedSolderJoint焊點(diǎn)REFLOW基本知識(shí)HeatTransferMechanisms

(加熱的方式)Heattransfermechanisms:Radiation(紅外線)Convection(對(duì)流)REFLOW基本知識(shí)RadiationHeatTransfer

(紅外線傳熱)Radiationmakesuseofradiantheattoheattheprocessarea.(通過(guò)紅外線的輻射來(lái)加熱各個(gè)溫區(qū))Coloroftargetcomponents(元件的顏色)Shadowing(明暗)Distanceoftheradiationsource(離發(fā)射口的距離)Frequency(頻率)REFLOW基本知識(shí)ConvectionHeatTransfer

(對(duì)流傳熱)Heatiscarriedtothechamberviasomemedia(熱量是通過(guò)一些媒介傳送到各個(gè)溫區(qū))

Usuallyamixtureofgases(通常是一種混合氣體)Solectronusesforceconvectionovens(旭電使用的是強(qiáng)制對(duì)流形式的爐子)AdvantagesofConvectionHeat(優(yōu)勢(shì))Velocityoftheflow(流通速度快)Efficientheatingpattern(經(jīng)濟(jì)的加熱形式)Chamberuniformlyheated(受熱均勻)REFLOW基本知識(shí)Equipment

回流焊設(shè)備BTUP1501.10個(gè)加熱區(qū)(HeatingZones)2.加熱方式－強(qiáng)制對(duì)流(ForceConvection)-AirAmplifier3.所用氣體－氮?dú)?空氣(N2/Air)4.冷卻方法－水冷(WaterCoolingSystem)5.1,2區(qū)預(yù)熱(Preheat)6.3,4,5,6,7,8區(qū)浸潤(rùn)(Soak)7.9-10區(qū)回流焊(Reflow)8.在1,3,5,7,9的

Top面上有壓力控制傳感器9.

有4個(gè)氣體放大器分別在1,2,9,10的Top上REFLOW基本知識(shí)AtmosphereCurtainAssembliesREFLOW基本知識(shí)GasAmplifier&FeedPlenumREFLOW基本知識(shí)GasFeedPlenumChambersREFLOW基本知識(shí)TypicalConvectionReflowProfile30-60sREFLOW基本知識(shí)TypicalReflowSolidificationStagesREFLOW基本知識(shí)BTUP150REFLOW基本知識(shí)Paragon150LayoutFluxCondenserHeatedSection10ZonesDoubleCoolingSectionLipVentExhaustLipVentExhaust150InchesofHeat10ZonesTop/Bottom2CoolingZonesFluxCondenserREFLOW基本知識(shí)SafetyLabelsCAUTION

!EMOEMERGENCYOFFOREMERGENCYSTOPBUTTON

(RedandWhite)

CAUTION

!Hotinternalsurface

usecautionwhenopeningthelid.MECHANICALORPINCHPOINTHAZARD

(YellowandBlack)TEMPERATUREHAZARD(YellowandBlack)EMERGENCYSTOPBUTTON(YellowandBlack)REFLOW基本知識(shí)SafetyLabelsELECRICALHAZARD

(RedandBlack)

DANGER

!Hotinternalsurface

usecautionwhenopeningthelid.ELECRICALHAZARD

(RedandBlack)DANGERHIGHVOLTAGE!CRUSHHAZARD(RedandBlack)ourhands.

DANGER

!VAPORHAZARD

(RedandBlack)

DANGER

!ThisequipmentcontainsRefractoryCeramicFibers(RCF)thathavebeenidentifiedbytheInternationalAgencyforResearchonCancer(IARC)asapossiblehumancarcinogen(Group

2B).ExposuretoRCFmaybehazardoustoyourhealth.Undernormaloperatingconditions,exposureshouldnotoccur.Ifmaintenanceistobeperformedonthisequipment,orifexposuretoRCFotherwiseoccurs,thenprecautionsshouldbetakenforthehandlingofRCF.ThenecessaryprecautionsandemergencyproceduresaredescribedintheMSDSsheetsincludedinthetechnicalmanualsuppliedwiththisequipment.FurtherinformationonRCFmayalsobeobtainedfrom:TheCarborundumCompany-FibersDivision.HOTLINENUMBER(716)278-2183.WARNING!TEMPERATUREHAZARD(YellowandBlack)TEMPERATUREHAZARD(YellowandBlack)REFLOW基本知識(shí)

步驟1準(zhǔn)備材料準(zhǔn)備有SMT元件的PCB

熱電偶(K型號(hào))耐高溫焊錫絲 310oC(5Sn/95Pb) 280oC(10Sn/90Pb) 183oC(63Sn/37Pb)

耐高溫膠帶提供足夠焊接溫度的電烙鐵在PCB板上選定被測(cè)位置：做溫度曲線步驟REFLOW基本知識(shí)

至少取三個(gè)焊點(diǎn)位置熱質(zhì)量高的區(qū)域熱質(zhì)量高的元件熱質(zhì)量低的區(qū)域注意：若有高溫敏感元件，則還應(yīng)測(cè)元件體溫度將熱電偶線焊在選定的位置用耐高溫膠帶將熱電偶線固定在PCB上

步驟2設(shè)定回流爐參數(shù)根據(jù)技術(shù)報(bào)告，了解所用焊膏回流的溫度要求*做溫度曲線的目的是確保焊膏能很好地回流而不是PCB 做溫度曲線步驟REFLOW基本知識(shí)做溫度曲線步驟

決定整個(gè)加熱時(shí)間設(shè)定程序參數(shù)

步驟3連接熱電偶線與溫度曲線接收器過(guò)回流爐 *重測(cè)溫度曲線之前，保證回流爐溫度已穩(wěn)定 *在再次使用前，須將PCB板和溫度曲線接收器冷卻到室溫

步驟4分析溫度曲線，調(diào)節(jié)回流爐參數(shù)REFLOW基本知識(shí)熱電偶工作原理

K型號(hào)熱偶線成分:NiCr/NiAl(熔融溫度.>300攝氏度)熱偶線溫度測(cè)量原理熱偶線測(cè)溫頭溫度溫度曲線接收器存儲(chǔ)器焊點(diǎn)溫度熱偶線電流熱偶線測(cè)溫頭阻抗計(jì)算機(jī)或打印機(jī)溫度曲線RS232軟件REFLOW基本知識(shí)有規(guī)律地，一致性地排放如何放板進(jìn)爐子

好好好壞壞REFLOW基本知識(shí)回流焊造成的缺陷1.沒有回流

焊膏沒回流/冷焊*回流焊曲線不正確---加熱溫度太低*焊點(diǎn)的熱量被旁邊的導(dǎo)熱體吸走*回流爐內(nèi)熱負(fù)載太大

缺焊*模板孔隙堵塞*印刷過(guò)程超出控制

未浸潤(rùn)*元件的可焊性不好*PCB的焊盤可焊性不好*元件與焊膏不接觸---檢查印刷的準(zhǔn)確性,板翹曲...*助焊劑活性不好或變干REFLOW基本知識(shí)回流焊造成的缺陷1.未回流

浸潤(rùn)太過(guò)*浸潤(rùn)時(shí)間太長(zhǎng)*焊盤的金屬間化合物過(guò)厚*片式元件可焊端對(duì)重金屬滲透阻擋不夠回流不均*不恰當(dāng)?shù)臏囟仍O(shè)置*熱傳遞太差*回流爐中熱傳遞不均勻*回流爐溫度調(diào)節(jié)能力不夠REFLOW基本知識(shí)回流焊造成的缺陷2.焊料球噴濺的焊料球*板中有水份*在浸潤(rùn)前助焊劑沒有完全干燥*預(yù)熱太快焊料球分散在焊盤周圍*焊膏塌陷*焊膏被擠到焊盤外或印刷錯(cuò)位*金屬顆粒氧化*助焊劑活性弱REFLOW基本知識(shí)回流焊造成的缺陷2.焊料球

片式元件兩側(cè)有焊料球*不正確的焊盤和模板設(shè)計(jì)PCB板上散亂的焊料球*焊膏粘在模板底面*印錯(cuò)的PCB沒有清洗干凈3.損壞PCB/元件

板燒焦*爐中溫度太高*加熱時(shí)間太長(zhǎng)*進(jìn)板頻率低于設(shè)置*在回流爐中放板位置不正確REFLOW基本知識(shí)回流焊造成的缺陷

損壞元件*溫度太高*熱沖擊*元件封裝中有水份3.損壞PCB/元件

*回流焊后冷卻不充分*冷卻太快*從回流爐出來(lái)后，板掉落而受到機(jī)械沖擊*板翹曲4.焊點(diǎn)斷裂或扭曲REFLOW基本知識(shí)回流焊造成的缺陷

*印刷不好或模板太薄*焊膏粘在模板孔隙中*焊錫從焊