ฝึกพูดภาษาอังกฤษด้วยเทคนิค Shadowing จากวิดีโอ: PCB Inspection Methods & Common PCB Defects
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140 ประโยค
หากประโยคสั้นหรือยาวเกินไป กดที่ Edit เพื่อปรับแก้
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This is the next video in the PCB series.
นี่คือวิดีโอต่อไปในซีรีส์ PCB
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Here we're going to be looking at printed circuit board assemblies and the inspection methods and common defects.
ในที่นี้ เราจะมาดูชุดแผ่นวงจรพิมพ์ รวมถึงวิธีการตรวจสอบและข้อบกพร่องที่พบบ่อย
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So checking solder paste process.
กำลังตรวจสอบกระบวนการวางสเปรย์บัดกรี
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There are a number of points to check for with the solder paste process.
มีจุดหลายประการที่ต้องตรวจสอบสำหรับกระบวนการวางสเปรย์บัดกรี
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1. We need to be looking at the paste stencil alignment.
1. เราต้องตรวจสอบการจัดตำแหน่งสเตนซิลสำหรับวางแผ่นแปะ
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If an automatic solder paste machine is being used, the general method is to use a camera to determine the position of the PCB by checking for the dooshals,
หากใช้เครื่องวางครีมบัดกรีอัตโนมัติ วิธีการทั่วไปคือการใช้กล้องกำหนดตำแหน่งของ PCB โดยตรวจสอบ dooshals
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alignment dots on the PCB.
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We covered this in a previous video.
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The manual method of setting up the stencil is to align the stencil with the PCB printed pads.
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then set the clamp stops to hold the PCB in the correct place.
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What to check for?
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Well you need to check the solder paste is correctly aligned to all of the pads on the PCB.
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Over on the right here we can see three images.
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The top image, which is good, shows that all of the paste is aligned with the pads.
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The middle shows some errors we can see here, slight misalignment and one bridge between two solder plates.
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The bottom one is just a mess, i.e. the ugly looking thing, with solder all over the place.
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Two, the squeegee speed and pressure.
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The squeegee speed should not be too fast that the paste does not roll as it moves across the stencil
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or too slow
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that the print cycle time does not keep up with the manufacturing line The blade pressure is usually set
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so that no paste remains on the stencil behind the squeegee
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Higher pressures will not only damage the stencil but also shear thin the paste
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to such an extent that the flux will separate from the metal and problems such as paste sticking to the blade,
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lack of tack at placement or poor solderability will occur further down the assembly line.
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What to check for?
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We need to check for solder paste is not left on the stencil after a pass
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and that all the solder pads have adequate paste deposited.
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Again on the right hand side here, going from the top left, 1, the alignment gasket of apertures to the pad.
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2, we need to check the squeegee motion, things paste so it flows into the apertures.
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3, bottom left, paste, recovers, stiffens up.
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And of 4, the bottom right, the stencil separates from PWB, paste deposits release from the stencil into the pads.
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Now let's have a look at the five major issues with pick and place machines.
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Fault number one, loss of vacuum.
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What to check for?
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Or primary process set up areas to check.
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Is nozzle damaged and will not sit flush against the component's surface?
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Or damaged vacuum hoses or a vacuum system?
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Fault number two, short or worn nozzles.
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What to check for?
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Short nozzles will result in components not being placed correctly resulting in component shift and movement.
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Worn nozzle tips result in loss of vacuum and you will see components being dropped.
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Measure nozzles against dimensional acceptance.
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Thought number 3.
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Sticking nozzles.
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What to check for?
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Damaged nozzles that do not fit correctly into their holders.
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old and non-maintained nozzles.
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On the right hand side there you can see the top image showing the nozzle area.
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Make sure these are not worn or damaged in any way.
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The bottom image just shows a variety of different nozzles that can be used.
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Thought number four, higher than normal reject rates at inspection.
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What to check for components were not presented to the nozzle in a consistent position,
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poor nozzle alightening from degradation of reflective discs or nozzle face over time,
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dirty reflective discs or nozzle face, a poor quality of reflective disc or nozzle face,
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nozzle height is incorrect, And finally, stuck nozzles from part height incorrect setting program.
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Nozzle worn beyond their tolerances or incorrect length tolerance on nozzles.
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Fault number 5.
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Component and circuit board damaged caused by ESD.
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What to check for?
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Ensure nozzles are manufactured from electrostatic dissipating materials.
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manufacturing manufacturers data sheet for this.
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What to check for with incorrect wave solder profile.
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Default here is bridging.
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What to check for?
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Well the primary process setup areas to check are conveyor speed too slow or other incorrect solder wave settings,
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time Overheat is too long causing flux to be burnt off.
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Dwell time is too long causing the flux to burn off before exiting the wave.
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Top side board temperature too low.
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Not enough flux applied to the flux activity is too low.
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You can see here in this image solder bridging between two points.
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the incorrect wave soldering profile issue, the fault being insufficient solder on topside fillet.
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What to check for?
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Conveyor speed is too low.
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Check the time over preheat too long, causing the flux to be burned off.
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Dwell time is too long, causing flux to be destroyed before exiting the wave.
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The conveyor speed is too fast.
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Dwell time is too short.
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topside board temperature too high for flux causing it to burn off before the wave, not enough flux or the flux is not active enough,
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solder temperature too low it cools in the barrel before it reaches the topside,
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and wave height too low in one or both waves so the solder does not contact the board properly.
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In this image it clearly shows there is insufficient solder to make this a good contact.
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Another incorrect wave solder profile issue
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so the fault here is insufficient solder bottom side fillet conveyor
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speed is too slow time over preheat too long causing the
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flux to be burnt off dwell time is too long causing flux to be destroyed before it exits the wave.
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Bottom side board temperature is too high causing flux to be burnt off before the wave
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and not enough flux or flux activity.
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The wave height is too low on one or both waves.
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And we can see here on the right hand side we've got problems with that connector.
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On the bottom is insufficient solder where this component is placed.
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Another incorrect wave solder profile issue, the fault here, is de-wetting or non-wetting.
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What to check for?
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Usually the board related due to contamination on the surface of the pads.
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Solder temperature too low, solder wave height too low, contaminated flux or contaminated solder.
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Or the conveyor speed is too high or too low.
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And again, we can see examples here of solder de-wetting or non-wetting in the bottom instance.
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Another incorrect wave solder profile issue is solder voids.
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Now what to check for here.
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Topside or overall board temperature is too low in trapping moisture that is outgassed at the wave.
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Entrapped fluid by component in through hole.
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Chemical contaminants not removed during PC fabrication process.
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Contamination in the hole.
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Top side of the hole covered by component body or flashing.
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You can see an example of a solder void here.
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Another fault is solder skip.
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Now what to check for?
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Conveyor speeds too fast.
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so the dwell was too short in the wave.
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Make sure the chip or turbine wave is turned on.
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Not enough flux for the solder to bond.
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Wave height too low on one or both waves.
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You can clearly see here this pad has no solder at all.
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Another fault is icicles or flags or horns.
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Now what to check for?
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conveyor speeds too slow.
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Time over preheat too long causing flux to burn off.
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Dwell time too long causing flux to be destroyed before exiting to the wave.
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Solar temperature too low, not enough flux.
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The use of nitrogen will help prevent icicles.
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You can see a good example here of what we're talking about when we mention solar flags.
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Another fault is solder on mask Poor flux application Flux and resist incompatibility Poor cure of the solder mask
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Preheat temperatures too high Solder temperature too high This image just shows the solder on the mask itself
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another fault is rough or disturbed solder check conveyor for vibration or jerky motion
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removal of the board prior to the solder solidifying solder temperature too low conveyor speed too high and wave run uneven
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you can see what we're talking about with rough solder in this image
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just to summarize here's an image of some common faults I'm
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just going to go through these with the top left moving to the right
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so we've got lifted component we've got tombstone effect
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wrong polarity upside down mounting in the second row we have a missing component
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we have that missing solder that we saw earlier we have a lifted lead
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we've got that solder bridging again
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on the bottom row we've got billboarding then we have shifted or twisted component we have our solder flags again
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and that solder void
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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 at all in China.
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Don't forget to like, share and subscribe to our channel.
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And you see there's a little bell symbol.
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If you hit that, you'll get a notification every time we upload new content.
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Thanks for listening.
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My name is Paul Adams from South East and I shall see you in the next video.
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คำศัพท์และข้อสังเกตด้านการพูดสำหรับบทเรียนนี้
วิดีโอนี้มี 140 ประโยค และ 1559 คำ สำหรับฝึกพูดตาม ช่วงที่มีเสียงพูดยาว 12:27 ผู้พูดพูดด้วยความเร็วสม่ำเสมอ ประมาณ 125 คำต่อนาที เหมาะกับการฝึกพูดตาม มีเพียง 76% ของคำที่อยู่ใน 3,000 คำที่ใช้บ่อยที่สุดในภาษาอังกฤษ คำศัพท์จึงค่อนข้างยาก
คำศัพท์สำคัญในวิดีโอนี้
คำที่ควรเรียนรู้ 15 คำจากวิดีโอ พร้อมคำอ่านและความหมาย:
| คำศัพท์ | คำอ่าน | ความหมาย |
|---|---|---|
| pasta คำนาม | /ˈpɑ.stə/ | พาสตา |
| incorrect คำคุณศัพท์ | /ˌɪn.kəˈɹɛkt/ | ผิด |
| dwell คำกริยา | /dwɛl/ | อาศัยอยู่, อยู่ |
| exit คำนาม | /ˈɛɡzət/ | ทางออก |
| vacuum คำนาม | /ˈvæ.kjuːm/ | สุญญากาศ |
| mask คำนาม | /mæsk/ | หน้ากาก |
| alignment คำนาม | /əˈlaɪn.mənt/ | การปรับแนว, การปรับตรง |
| deposit คำนาม | /dɪˈpɑ.zɪt/ | เงินฝาก |
| blade คำนาม | /bleɪd/ | ใบ, มีด |
| extent คำนาม | /ɪkˈstɛnt/ | ขอบข่าย, ขนาด |
| occur คำกริยา | /əˈkɜː/ | เกิด |
| thin คำคุณศัพท์ | /ˈθɪn/ | บาง |
| ugly คำคุณศัพท์ | /ˈʌɡli/ | น่าเกลียด |
| sheet คำนาม | /ʃit/ | แผ่น |
| automatic คำคุณศัพท์ | /ˌɔː.təˈmæt.ɪk/ | อัตโนมัติ |
การออกเสียงที่ควรระวัง
ผู้พูดใช้รูปย่อและรูปลดเสียง 12 ครั้ง เช่น we've, we're, don't ให้พูดแบบสั้นตามที่ได้ยิน
- เสียง “sh” และ “zh”: insufficient /ɪnsəˈfɪʃənt/, inspection /ɪnˈspɛkʃən/, contamination /kənˌtæm.əˈneɪ.ʃən/, flash /flæʃ/, sheet /ʃit/
- คำยาว — ลงเสียงหนักให้ถูกพยางค์: insufficient /ɪnsəˈfɪʃənt/, contamination /kənˌtæm.əˈneɪ.ʃən/, automatic /ˌɔː.təˈmæt.ɪk/, manufacturer /ˌmænjʊˈfæktʃəɹə/, dimensional /daɪˈmɛn.ʃə.nəl/
วิธีฝึกกับวิดีโอนี้
- ฟังวิดีโอให้จบหนึ่งรอบโดยยังไม่ต้องพูด แล้วจดคำที่ยังไม่รู้จัก
- พูดตามทีละประโยคด้วยความเร็วปกติ ทำซ้ำแต่ละประโยคจนจังหวะของคุณตรงกับผู้พูด
- อัดเสียงตัวเองแล้วเทียบกับต้นฉบับ โดยสังเกตคำอย่าง pasta, incorrect, dwell เป็นพิเศษ
เทคนิค Shadowing คืออะไร?
Shadowing เป็นเทคนิคการเรียนรู้ภาษาที่ได้รับการรับรองทางวิทยาศาสตร์ พัฒนาขึ้นสำหรับการฝึกนักแปลมืออาชีพ วิธีการนี้เรียบง่ายแต่ทรงพลัง: คุณฟังเสียงภาษาอังกฤษจากเจ้าของภาษาและพูดตามทันที — เหมือนเงาที่ตามผู้พูดด้วยช่วงเวลาห่าง 1-2 วินาที การวิจัยแสดงว่าเทคนิคนี้ปรับปรุงความแม่นยำในการออกเสียง ทำนองเสียง จังหวะ การเชื่อมเสียง การฟังเข้าใจ และความคล่องแคล่วในการพูดได้อย่างมีนัยสำคัญ