跟讀練習: What is SMT (Surface Mount Technology)? PCB Assembly (Part 1) - 通過影片學習英語口語

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Music Welcome to the next video in the series of PCBs.

Here we're going to be looking at what is an SMT.

So using a surface mount technology to assemble PCBs Part 1.

Surface Mount Technology Overview.

Now, Surface Mount Technology, which is the SMT, is a method for producing electrical circuits in which the components are mounted

or placed directly onto the surface of printed circuit boards or PCBs.

An electrical device that is soldered to the PCB is called a Surface Mount Device or an SMD for short.

By employing SMT, the production process speeds up

but the risk of defects also increases due to the component miniaturization and to the denser packing of boards.

In these conditions, detection of failures has become critical for any SMT manufacturing process.

Let's have a look at the PCBA production process.

So manufacturing PCBs with SMA techniques.

Manufacturing of printed circuit boards with an automated surface mount assembly,

or SMA line, consists of the following sequence of operations.

Solder paste application Component placement reflow soldering, cleaning and electrical test In this video,

we will concentrate on the first two steps in this process.

So we'll look at preassembly steps.

So the PCB design and manufacture.

Once the PCB has been designed and the components selected, it is time to get the PCB produced and the components ordered.

PCBs that are populated on a serviceman assembly line are normally produced in panel formats, as shown on the right hand side here.

The SMDs come packaged in different methods from trays for larger components and on tape bound on a reel for smaller components.

All the SMDs need to be sourced and made ready to load into the manufacturing line machines.

SodaPaste application Let's have a look at the solder paste application process.

So once the PCB is loaded into the machine, the stencil is positioned over the panels.

Solder paste is then added in front of the squeegee.

Let's have a look at that in a diagram format.

So we can see here the stencil is lowered onto the PCB, the squeegee is in position,

and the solder paste loaded just before the squeegee.

The squeegee lowers onto the stencil such that it is applying a very specific amount of pressure.

The squeegee moves along the length of the stencil while the solder paste is deposited into the stencil apertures.

And you can see that in this image here,

where the squeegee has completed its journey and left the solder deposits in the stencil apertures.

At the end of the travel, the squeegee raises up and the stencil is separated from the panels.

That is depicted here in this image.

You can see the stencil is raised leaving the soda paste on the correct positions on the pads.

Solder paste issues.

So this first one is the acceptable deposit onto a pad.

This is what it should be looking like.

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.

Scavenged deposits of solder, and this is where the middle has been scooped out, and you can see that here.

Ridging is where a solid paste is connected between Two pads.

The last one we're going to look at is peaking or dog ears effect.

And you can see that depicted here.

So component placement process Let's have a look at that in the PCB design and manufacture.

So basic placement sequence generally includes board indexing,

board registration, fiducial vision alignment, component pickup component centering or vision inspection,

component placement and board indexing, and automated optical inspection, Component pickup.

component centering and vision inspection, component placement are repeated for each component.

And you can see an example of a component placed on the wet soda pads here.

Thank you.

Let's have a look at PCB positioning.

and the PCB positioning method.

Through the process of board indexing, The PCP is loaded to the appropriate position.

Fiducial marks provide common measurable points for all steps in the assembly process.

The three main types of fiduciary marks are: 1.

Panel.

This is a global fiducial mark on a multiple printed circuit board fabrication panel

that are located outside the parameters of the end product printed circuit boards.

You can see an example of that here.

2. Global.

These are fiduciary marks used to locate the position of all the features on an individual printed circuit port.

Again, this is shown here. And three, local.

These are fiduciary marks or marks used to locate the position of an individual allowance pattern

or component that may require more precision location such as a QFP.

and again you can see that here in this image Pick and place types.

Let's have a look at the chip shooter type.

Now chip shooters are generally fast.

They can range between 20 ,000 and 80 ,000 placements per hour

and can even range up to 100 ,000 placements per hour with relatively low accuracy, generally in a range of 70 microns.

As a result, chip shooters are not generally used for placing a active components which require better accuracy.

There are three major types of chip shooters Stationary turret overhead gantry and revolver head.

You can see an example of a chip shooter in this picture here.

Let's have a look at a flexible placer type Now comparing to chip shooters, these are flexible places are slow.

and they range between 6 ,000 to 40 ,000 placements per hour.

But they have a high accuracy, as low as 25 microns.

As a result, flexible placers are used to place complex and high I -O active components,

such as QFPs, as high -performance I -O components generally require higher accuracy.

There are three major types of flexible placer, Split axes.

Thank you.

Vacuum nozzles and grips.

Let's have a look at vacuum nozzles.

Vacuum nozzles are commonly used for handling all the components during the placement operations.

There are a variety of vacuum nozzle sizes for different component sizes.

For handling small components, positive pressure is often supplied in addition to vacuum at the moment of placement

so that the component will be completely released from the nozzle.

You can see a selection of vacuum nozzles in this image here.

You can see the different sizes for the vacuum pickup.

We also have mechanical grips.

Self -centering mechanical grippers allow simultaneous pickup and automatic centering without a need for vacuum.

A pair of tweezer type grippers would hold the part while centering it along one axis.

Vision inspection.

Upward facing vision system.

The vision inspection part of the process checks the critical components have been picked correctly.

their orientation and other features such as Pin 1 location.

All of this data is then fed into the machine to

ensure the device is placed into position with the highest accuracy possible.

Inline Automated Optical Inspection or AOI.

AOI is an automated visual inspection for printed circuit board manufacture

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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本課的詞彙與口語要點

這節 C1 級別的口語課以影片“What is SMT (Surface Mount Technology)? PCB Assembly”為素材。影片中反覆出現的詞有：component, Pcb, placement, board, solder。這段影片共有 108 個句子、1290 個單詞可供跟讀。講話部分時長為 10:18。說話人語速平穩，每分鐘約 125 個詞，很適合跟讀。只有 72% 的單詞屬於英語最常用的 3,000 詞，詞彙難度較高。

影片中的重點詞彙

影片中最難的 15 個單詞，附發音和釋義：

單詞	發音	釋義
solder 名詞	/ˈsɒl.də(ɹ)/	焊料
placement 名詞	/ˈpleɪ̯smənt/	放置, 安置
pasta 名詞	/ˈpɑ.stə/	мянфан, 義大利麵 /義大利麵
stencil 名詞	/ˈstɛnsəl/	漏字版, 蠟紙 /蠟紙
vacuum 名詞	/ˈvæ.kjuːm/	真空
squeegee 名詞	/ˈskwiˌd͡ʒi/	刮刀刮水刷
shooter 名詞	/ˈʃuːtəː/	射手
automate 動詞	/ˈɔ.təˌmeɪt/	自動化 /自動化
fiduciary 名詞	/fəˈduːʃ.i.eɹ.i/	受託人 /受託人, 受託者 /受託者
pad 名詞	/pæd/	墊 /墊, 墊子 /墊子
aperture 名詞	/ˈæp.ɚˌt͡ʃʊɹ/	孔
depict 動詞	/dɪˈpɪkt/	描繪 /描繪, 描述
micron 名詞	/ˈmaɪkɹɒn/	微米
defect 名詞	/ˈdiːfɛkt/	缺點 /缺點, 問題 /問題
soda 名詞	/ˈsoʊdə/	蘇打 /蘇打, 碳酸鈉 /碳酸鈉

影片中出現的短語動詞

單詞	發音	釋義
check out 動詞		退房
speed up 動詞	/spiːdˈʌp/	加速, 加快

影片中的語法

說話人最常用的結構，並附上影片中的原話：

結構	影片中的用法
被動語態 be + 過去分詞 — 強調發生了什麼，而不是誰做的	are mounted · is soldered · has been designed
現在完成時 have/has + 過去分詞 — 過去發生但與現在仍有關聯的事	has become · has been designed · has completed

需要注意的發音

說話人用了 5 次縮略和弱讀形式，例如 don't, we're, we'll。請按聽到的簡短形式來說。

“sh” 和 “zh” 音: shooter /ˈʃuːtəː/, fiducial /fəˈd(j)uːʃəl/, fiduciary /fəˈduːʃ.i.eɹ.i/, fabrication /fæbɹɪˈkeɪʃən/, measurable /ˈmɛʒəɹəbəl/
長單詞——注意重音位置: fiduciary /fəˈduːʃ.i.eɹ.i/, fabrication /fæbɹɪˈkeɪʃən/, measurable /ˈmɛʒəɹəbəl/, simultaneous /ˌsaɪ̯.məlˈteɪ̯.ni.əs/, parameter /pəˈɹæm.ə.tɚ/

中文母語者容易讀錯的音：

/v/ — 不要讀成 /w/，上齒輕觸下唇: vacuum /ˈvæ.kjuːm/, revolver /ɹɪˈvɒl.vɚ/, scavenge /ˈskæv.ɪndʒ/, overhead /ˈəʊvəˌhɛd/
詞尾子音 — 要讀清楚，後面不要加母音: placement /ˈpleɪ̯smənt/, automate /ˈɔ.təˌmeɪt/, locate /ˈloʊˌkeɪt/, pad /pæd/, depict /dɪˈpɪkt/
/r/ 和 /l/ 的區別: solder /ˈsɒl.də(ɹ)/, placer /ˈpleɪsə(ɹ)/, measurable /ˈmɛʒəɹəbəl/, revolver /ɹɪˈvɒl.vɚ/, reel /ˈɹiːl/

如何用這段影片練習

先完整聽一遍影片，不要開口，記下不認識的單詞。
用正常速度逐句跟讀，每句重複到你的節奏與說話人一致為止。
錄下自己的聲音並與原聲對比，特別注意 solder, placement, pasta 這類單詞。

什麼是跟讀法？

跟讀法 (Shadowing) 是一種有科學依據的語言學習技巧，最初開發用於專業口譯員的培訓，並由多語言者Alexander Arguelles博士普及。這個方法簡單而強大：您在聽英語母語原聲的同時立即大聲重複——就像是一個延遲1-2秒緊跟說話者的影子。與被動聽力或語法練習不同，跟讀法強迫您的大腦和口腔肌肉同時處理並模模擬實的講話模式。研究表明它能顯著提高發音準確性，語調，節奏，連讀，聽力理解和口語流利度——使其成為雅思口語備考和真實英語交流最有效的方法之一。

影子跟讀法: 閱讀完整分步指南 →

跟讀練習: What is SMT (Surface Mount Technology)? PCB Assembly (Part 1) - 通過影片學習英語口語

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