Prática de Shadowing: What is SMT (Surface Mount Technology)? PCB Assembly (Part 1) - Aprenda a falar inglês com vídeo
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Music Welcome to the next video in the series of PCBs.
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Here we're going to be looking at what is an SMT.
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So using a surface mount technology to assemble PCBs Part 1.
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Surface Mount Technology Overview.
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Now, Surface Mount Technology, which is the SMT, is a method for producing electrical circuits in which the components are mounted
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or placed directly onto the surface of printed circuit boards or PCBs.
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An electrical device that is soldered to the PCB is called a Surface Mount Device or an SMD for short.
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By employing SMT, the production process speeds up
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but the risk of defects also increases due to the component miniaturization and to the denser packing of boards.
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In these conditions, detection of failures has become critical for any SMT manufacturing process.
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Let's have a look at the PCBA production process.
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So manufacturing PCBs with SMA techniques.
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Manufacturing of printed circuit boards with an automated surface mount assembly,
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or SMA line, consists of the following sequence of operations.
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Solder paste application Component placement reflow soldering, cleaning and electrical test In this video,
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we will concentrate on the first two steps in this process.
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So we'll look at preassembly steps.
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So the PCB design and manufacture.
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Once the PCB has been designed and the components selected, it is time to get the PCB produced and the components ordered.
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PCBs that are populated on a serviceman assembly line are normally produced in panel formats, as shown on the right hand side here.
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The SMDs come packaged in different methods from trays for larger components and on tape bound on a reel for smaller components.
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All the SMDs need to be sourced and made ready to load into the manufacturing line machines.
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SodaPaste application Let's have a look at the solder paste application process.
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So once the PCB is loaded into the machine, the stencil is positioned over the panels.
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Solder paste is then added in front of the squeegee.
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Let's have a look at that in a diagram format.
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So we can see here the stencil is lowered onto the PCB, the squeegee is in position,
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and the solder paste loaded just before the squeegee.
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The squeegee lowers onto the stencil such that it is applying a very specific amount of pressure.
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The squeegee moves along the length of the stencil while the solder paste is deposited into the stencil apertures.
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And you can see that in this image here,
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where the squeegee has completed its journey and left the solder deposits in the stencil apertures.
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At the end of the travel, the squeegee raises up and the stencil is separated from the panels.
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That is depicted here in this image.
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You can see the stencil is raised leaving the soda paste on the correct positions on the pads.
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Solder paste issues.
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So this first one is the acceptable deposit onto a pad.
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This is what it should be looking like.
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Some of the issues that could follow are: Slumped deposit of solder paste onto the pad, which just looks like it's just dumped on.
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Scavenged deposits of solder, and this is where the middle has been scooped out, and you can see that here.
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Ridging is where a solid paste is connected between Two pads.
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The last one we're going to look at is peaking or dog ears effect.
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And you can see that depicted here.
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So component placement process Let's have a look at that in the PCB design and manufacture.
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So basic placement sequence generally includes board indexing,
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board registration, fiducial vision alignment, component pickup component centering or vision inspection,
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component placement and board indexing, and automated optical inspection, Component pickup.
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component centering and vision inspection, component placement are repeated for each component.
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And you can see an example of a component placed on the wet soda pads here.
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Thank you.
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Let's have a look at PCB positioning.
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and the PCB positioning method.
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Through the process of board indexing, The PCP is loaded to the appropriate position.
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Fiducial marks provide common measurable points for all steps in the assembly process.
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The three main types of fiduciary marks are: 1.
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Panel.
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This is a global fiducial mark on a multiple printed circuit board fabrication panel
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that are located outside the parameters of the end product printed circuit boards.
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You can see an example of that here.
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2. Global.
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These are fiduciary marks used to locate the position of all the features on an individual printed circuit port.
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Again, this is shown here. And three, local.
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These are fiduciary marks or marks used to locate the position of an individual allowance pattern
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or component that may require more precision location such as a QFP.
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and again you can see that here in this image Pick and place types.
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Let's have a look at the chip shooter type.
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Now chip shooters are generally fast.
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They can range between 20 ,000 and 80 ,000 placements per hour
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and can even range up to 100 ,000 placements per hour with relatively low accuracy, generally in a range of 70 microns.
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As a result, chip shooters are not generally used for placing a active components which require better accuracy.
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There are three major types of chip shooters Stationary turret overhead gantry and revolver head.
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You can see an example of a chip shooter in this picture here.
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Let's have a look at a flexible placer type Now comparing to chip shooters, these are flexible places are slow.
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and they range between 6 ,000 to 40 ,000 placements per hour.
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But they have a high accuracy, as low as 25 microns.
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As a result, flexible placers are used to place complex and high I -O active components,
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such as QFPs, as high -performance I -O components generally require higher accuracy.
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There are three major types of flexible placer, Split axes.
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Thank you.
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Vacuum nozzles and grips.
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Let's have a look at vacuum nozzles.
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Vacuum nozzles are commonly used for handling all the components during the placement operations.
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There are a variety of vacuum nozzle sizes for different component sizes.
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For handling small components, positive pressure is often supplied in addition to vacuum at the moment of placement
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so that the component will be completely released from the nozzle.
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You can see a selection of vacuum nozzles in this image here.
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You can see the different sizes for the vacuum pickup.
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We also have mechanical grips.
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Self -centering mechanical grippers allow simultaneous pickup and automatic centering without a need for vacuum.
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A pair of tweezer type grippers would hold the part while centering it along one axis.
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Vision inspection.
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Upward facing vision system.
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The vision inspection part of the process checks the critical components have been picked correctly.
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their orientation and other features such as Pin 1 location.
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All of this data is then fed into the machine to
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ensure the device is placed into position with the highest accuracy possible.
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Inline Automated Optical Inspection or AOI.
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AOI is an automated visual inspection for printed circuit board manufacture
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where a camera autonomously scans the device under test for both catastrophic failure, in other words missing component,
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and quality defects such as fillet size or shape of component skew.
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And this is what that looks like.
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See the difference between these two.
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One is up facing and the other is down facing or in this case, top and bottom vision.
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Don't forget to check out our other videos in this PCB series
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and you can contact us if you need any help with your projects in China.
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So don't forget to like, share and subscribe to our channel.
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And if you hit this little bell symbol that will notify you of every new content that we upload.
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So thanks for listening, my name is Paul Adams and I shall see you in the next video.
📺 Mesmo canal
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Vocabulário e dicas de fala para esta lição
Esta aula de conversação de nível C1 usa o vídeo “What is SMT (Surface Mount Technology)? PCB Assembly”. As palavras que mais se repetem: component, Pcb, placement, board, solder. Este vídeo tem 108 frases e 1290 palavras para praticar shadowing. A fala dura 10:18. O falante mantém um ritmo estável de cerca de 125 palavras por minuto, confortável para o shadowing. Apenas 72% das palavras estão entre as 3.000 mais comuns do inglês, por isso o vocabulário é exigente.
Vocabulário principal deste vídeo
As 15 palavras mais avançadas do vídeo, com pronúncia e significado:
| Palavra | Pronúncia | Significado |
|---|---|---|
| solder substantivo | /ˈsɒl.də(ɹ)/ | solda |
| placement substantivo | /ˈpleɪ̯smənt/ | colocação, posicionamento |
| pasta substantivo | /ˈpɑ.stə/ | massa, macarrão |
| stencil substantivo | /ˈstɛnsəl/ | estêncil, régua vazada |
| vacuum substantivo | /ˈvæ.kjuːm/ | vácuo |
| squeegee substantivo | /ˈskwiˌd͡ʒi/ | rodo |
| nozzle substantivo | /ˈnɒzəl/ | bocal |
| shooter substantivo | /ˈʃuːtəː/ | atirador, atiradora |
| automate verbo | /ˈɔ.təˌmeɪt/ | automatizar |
| locate verbo | /ˈloʊˌkeɪt/ | localizar |
| aperture substantivo | /ˈæp.ɚˌt͡ʃʊɹ/ | abertura |
| depict verbo | /dɪˈpɪkt/ | representar, retratar |
| micron substantivo | /ˈmaɪkɹɒn/ | mícron, micrómetro |
| defect substantivo | /ˈdiːfɛkt/ | defeito |
| soda substantivo | /ˈsoʊdə/ | soda cáustica |
Phrasal verbs que você vai ouvir
| Palavra | Significado |
|---|---|
| check out verbo | verificar, sacar só |
Gramática neste vídeo
As estruturas que o falante mais usa, com as palavras exatas do vídeo:
| Estrutura | No vídeo |
|---|---|
| “Used to” used to + verbo — um hábito ou estado do passado que não é mais verdade | used to locate |
| Voz passiva be + particípio passado — o foco está no que acontece, não em quem faz | are mounted · is soldered · has been designed |
| Present perfect have/has + particípio passado — uma ação passada que ainda importa agora | has become · has been designed · has completed |
Pronúncia para ficar de olho
O falante usa 5 contrações e formas reduzidas, como don't, we're, we'll. Diga-as na forma curta, do jeito que você ouve.
- Os sons de “sh” e “zh”: shooter /ˈʃuːtəː/, fiducial /fəˈd(j)uːʃəl/, fiduciary /fəˈduːʃ.i.eɹ.i/, fabrication /fæbɹɪˈkeɪʃən/, measurable /ˈmɛʒəɹəbəl/
- Palavras longas — acerte a sílaba tônica: fiduciary /fəˈduːʃ.i.eɹ.i/, fabrication /fæbɹɪˈkeɪʃən/, measurable /ˈmɛʒəɹəbəl/, simultaneous /ˌsaɪ̯.məlˈteɪ̯.ni.əs/, parameter /pəˈɹæm.ə.tɚ/
Sons difíceis para falantes de português:
- Consoante final — sem acrescentar um “i” depois: placement /ˈpleɪ̯smənt/, automate /ˈɔ.təˌmeɪt/, locate /ˈloʊˌkeɪt/, pad /pæd/, depict /dɪˈpɪkt/
- /l/ final — a língua toca o céu da boca, não vira “u”: stencil /ˈstɛnsəl/, nozzle /ˈnɒzəl/, fiducial /fəˈd(j)uːʃəl/, optical /ˈɑptɪkəl/, measurable /ˈmɛʒəɹəbəl/
- s + consoante no início — sem um “i” antes: stencil /ˈstɛnsəl/, squeegee /ˈskwiˌd͡ʒi/, scavenge /ˈskæv.ɪndʒ/, scoop /skup/, scan /skæn/
Como praticar com este vídeo
- Ouça o vídeo inteiro uma vez sem falar e anote as palavras que você não conhece.
- Faça shadowing frase por frase na velocidade normal, repetindo cada uma até o seu ritmo ficar igual ao do falante.
- Grave a sua voz e compare com o original, prestando atenção a palavras como solder, placement, pasta.
O que é a Técnica de Shadowing?
Shadowing é uma técnica de aprendizado de idiomas com base científica, originalmente desenvolvida para o treinamento de intérpretes profissionais. O método é simples, mas poderoso: você ouve áudio em inglês nativo e repete imediatamente em voz alta — como uma sombra seguindo o falante com 1-2 segundos de atraso. Pesquisas mostram melhora significativa na precisão da pronúncia, entonação, ritmo, sons conectados, compreensão auditiva e fluência na fala.