Shadowing Practice: What is SMT (Surface Mount Technology)? PCB Assembly (Part 1) - Learn English Speaking with Video
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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.
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אוצר מילים והערות הגייה לשיעור הזה
שיעור הדיבור הזה ברמה C1 מבוסס על הסרטון “What is SMT (Surface Mount Technology)? PCB Assembly”. המילים שחוזרות הכי הרבה: component, Pcb, placement, board, solder. בסרטון הזה יש 108 משפטים ו-1290 מילים לתרגול Shadowing. הדיבור נמשך 10:18. הדובר שומר על קצב יציב של כ-125 מילים בדקה, קצב נוח לתרגול Shadowing. רק 72% מהמילים נמצאות בין 3,000 המילים הנפוצות ביותר באנגלית, כך שאוצר המילים מאתגר.
אוצר מילים מרכזי בסרטון הזה
15 המילים המתקדמות ביותר בסרטון, עם ההגייה והמשמעות שלהן:
| מילה | הגייה | משמעות |
|---|---|---|
| solder שם עצם | /ˈsɒl.də(ɹ)/ | לחם |
| placement שם עצם | /ˈpleɪ̯smənt/ | מיקום |
| pasta שם עצם | /ˈpɑ.stə/ | פַּסְטָה |
| stencil שם עצם | /ˈstɛnsəl/ | סְטֶנְסִיל, שַׁבְּלוֹנָה |
| vacuum שם עצם | /ˈvæ.kjuːm/ | ואקום, ריק |
| squeegee שם עצם | /ˈskwiˌd͡ʒi/ | מַגֵּב |
| nozzle שם עצם | /ˈnɒzəl/ | מַזְנֵק |
| fiducial שם תואר | /fəˈd(j)uːʃəl/ | מְהֵימָן |
| defect שם עצם | /ˈdiːfɛkt/ | פגם |
| optical שם תואר | /ˈɑptɪkəl/ | אופטי |
| revolver שם עצם | /ɹɪˈvɒl.vɚ/ | אֶקְדָּח |
| assemble פועל | /əˈsɛm.bəl/ | אסף |
| upward תואר הפועל | /ˈʌpwɚd/ | מַעְלָה |
| tray שם עצם | /tɹeɪ/ | מַגָּשׁ |
| axe שם עצם | /æks/ | גַּרְזֶן |
דקדוק בסרטון הזה
המבנים שהדובר משתמש בהם הכי הרבה, עם המילים המדויקות מהסרטון:
| מבנה | בסרטון |
|---|---|
| סביל (Passive voice) be + past participle — הדגש הוא על מה שקורה, לא על מי שעושה את הפעולה | are mounted · is soldered · has been designed |
| הווה מושלם (Present perfect) have/has + past participle — פעולה שקרתה בעבר ועדיין יש לה חשיבות או השפעה עכשיו | has become · has been designed · has completed |
הגייה ששווה לשים לב אליה
הדובר משתמש ב-5 קיצורים וצורות מקוצרות, כמו don't, we're, we'll. אמרו אותם בצורה הקצרה, כפי שאתם שומעים אותם.
- הצלילים של “sh” ו-“zh”: shooter /ˈʃuːtəː/, fiducial /fəˈd(j)uːʃəl/, fiduciary /fəˈduːʃ.i.eɹ.i/, fabrication /fæbɹɪˈkeɪʃən/, measurable /ˈmɛʒəɹəbəl/
- מילים ארוכות — שימו לב להטעמה: fiduciary /fəˈduːʃ.i.eɹ.i/, fabrication /fæbɹɪˈkeɪʃən/, measurable /ˈmɛʒəɹəbəl/, simultaneous /ˌsaɪ̯.məlˈteɪ̯.ni.əs/, parameter /pəˈɹæm.ə.tɚ/
צלילים שדוברי עברית מתקשים בהם:
- /w/ — שפתיים מעוגלות, לא /v/: squeegee /ˈskwiˌd͡ʒi/, upward /ˈʌpwɚd/
- /æ/ — פתוח יותר מה-“אֶ” העברית, לא כמו “a” ב-“cup”: vacuum /ˈvæ.kjuːm/, pad /pæd/, aperture /ˈæp.ɚˌt͡ʃʊɹ/, fabrication /fæbɹɪˈkeɪʃən/, gantry /ˈɡæntɹi/
- /r/ — הלשון לא נוגעת בשום מקום, לא ה-“ר” הגרונית: solder /ˈsɒl.də(ɹ)/, fiduciary /fəˈduːʃ.i.eɹ.i/, placer /ˈpleɪsə(ɹ)/, aperture /ˈæp.ɚˌt͡ʃʊɹ/, gripper /ˈɡɹɪ.pəɹ/
איך לתרגל עם הסרטון הזה
- הקשיבו לכל הסרטון פעם אחת בלי לדבר, ורשמו את המילים שאתם לא מכירים.
- תרגלו Shadowing משפט אחר משפט במהירות רגילה, וחזרו על כל משפט עד שהקצב שלכם תואם את הדובר.
- הקליטו את עצמכם והשוו למקור, תוך תשומת לב למילים כמו solder, placement, pasta.
מהי טכניקת השאדואינג?
שאדואינג היא טכניקת למידת שפה מבוססת מדע שפותחה במקור להכשרת מתורגמנים מקצועיים ופופולרית על ידי הפוליגלוט ד"ר אלכסנדר ארגואלס. השיטה פשוטה אך עוצמתית: אתה מקשיב לאודיו באנגלית ילידית וחוזר עליו בקול רם מיד — כמו צל העוקב אחרי הדובר עם עיכוב של 1–2 שניות בלבד. בניגוד להאזנה פסיבית או תרגילי דקדוק, שאדואינג מכריח את המוח והשרירים בפה לעבד ולשחזר דפוסי דיבור אמיתיים בו זמנית. מחקרים מראים שזה משפר משמעותית את דיוק ההגייה, האינטונציה, הקצב, הדיבור המחובר, הבנת השמיעה ושטף הדיבור — מה שהופך אותו לאחת השיטות היעילות ביותר להכנה לIELTS Speaking ולתקשורת באנגלית בעולם האמיתי.