エレクトロニクスにおけるSMTとは

Overview: The process of making technology smaller is moving at an increasingly faster pace that never stops amazing us. The only factor that makes the gradual shrinking of electronics conceivable is using a suitable, automatic SMT (surface-mount technology) assembly process. Instead of using standard components connected by wires (through-hole), this method allows for boards to be covered with smaller components that can be mounted directly on the surface.

The term ‘SMT’ may not be unfamiliar to electronic enthusiasts, but some may not know what it actually means. In fact, we have long been unable to leave the use of this patch technology, and you can find traces of SMT technology in various consumer electronic PCBA such as mobile phones, laptops, refrigerators, and TVs. In this article, FS Technology will introduce you to one of the most important parts of the PCB組立工程: SMT PCBA (PCB assembly).

SMTは製造業では何を意味するのか

Surface mount technology is commonly abbreviated to SMT and this type of technology is frequently used together with THT (through-hole technology) in the assembly process of circuit boards. This high-precision electronic assembly technique is used to attach or solder surface mount components onto PCB pads. Its workflow is roughly described below.

Firstly, solder paste is coated on the PCB pads. Then the surface mount components (SMD) are placed accurately on the solder paste-coated pads by heating the printed circuit board until the solder paste melts. After cooling an electrical connection will be established between the components and the printed circuit.

SMT技術に関連する用語の紹介

SMD: This stands for surface mount components, and PCB assembly companies usually use SMT technology to solder SMD components to the surface of electronic PCBA. If you want to know more about the difference between the two, you can read another article called “SMDとSMTの比較” in FS Technology’s PCBA blog.

THT: Known as through-hole technology, this term describes assembly technology used in the electronics industry, such as SMT. With THT, various types of components are welded on the surface of the PCBA board of electronic products where some are connected through patch elements and others are connected through plug-in components. THT enables the use of both service and plug-in components.

DIP: This term stands for dual in-line package. Its relationship with THT is similar to the relationship between SMT and SMD, but for some reason, we prefer to call it ディップアッセンブリー or through-hole assembly, rather than THT assembly.

SMTプロセスのコンセプト

In the SMT process, we often use two high-temperature welding processes to complete the welding of components: reflow soldering and wave soldering. So, in the SMT production line, what is the role of reflow soldering and wave soldering, and what is the difference between them? This section will answer the above questions for you.

Regarding リフローはんだ付け, soldering paste is first pre-coated on the pad and is subsequently melted by heating. This heating process will establish an electrical interconnection between the pins or solder ends of the electronic components premounted on the pad, and the PCB pad. This process essentially achieves the purpose of welding the electronic components onto the PCB board. Reflow welding is generally divided into three separate stages/zones: preheating zone, heating zone and cooling zone.

In short, the reflow soldering process can be summarized in these steps: print solder paste > mount components > reflow soldering > PCBA cleaning

Regarding ウエーブソルダリング, this is a type of bulk soldering process where a special pump is first used to spray melted solder into a solder wave peak. After that, the pins of the electronic components to be welded are passed through the solder wave peak to establish an electrical interconnection between the electronic components and the PCB board. The wave soldering process can be divided into these four steps: spraying, preheating, heating (in a tin furnace) and cooling.

These are the steps to summarize the wave soldering process: plug-in > flux coating > preheating > wave soldering > edge cutting > プリント基板実装検査.

ウェーブソルダリングとリフローソルダリングの主な違いは次のとおりです。

With reflow soldering, the PCB boards are already coated with solder paste before they enter the machine. Welding is then performed by melting the solder paste that is applied onto the board pads. Contrastingly, with wave soldering, there is no solder paste that is coated on the PCB before it enters into a machine. Instead, welding by wave soldering is performed with a machine that creates the solder paste to paint on the PCB pads which require solder.
Wave soldering uses molten solder to form solder waves for welding components whereas reflow soldering requires high temperatures and hot air to form circumfluence molten solder that is used to weld components.
Reflow soldering is mostly suitable for patch electronic components whereas wave soldering is more suitable for pin electronic components.

Now that the processes of wave soldering and reflow soldering are highlighted, including the main differences between the two, it is important to consider that they both are equally important processes in SMT Assembly machining.

表面実装技術の歴史

To get a clear idea of what a type of technology stands for, you have to understand its history. The development of SMT technology can be divided into four stages and the below section will explain each time period and any important characteristics as follows:

第1期：1960年～1975年

This stage was a historic moment when circuit boards came out and changed the electronics manufacturing industry. In this phase, humans have changed from using primitive breadboards to PCBA boards, and have completely entered the era of miniaturization. The representative works of this stage are calculators and quartz watches.

Phase 2: 1976 to 1980

A stage in which SMT technology becomes mainstream. Before this period, THT technology was mainly used for circuit board assembly, but with the popularity of small-volume electronic products all over the world, SMT gradually began to replace THT. Using this PCB assembly technique allows electronics to have a smaller footprint and be more functional. The main representative works are camcorders, video recorders and digital cameras.

Phase 3: 1980 to 1995

PCBAボードはエレクトロニクス製造業に欠かせない製品になり、企業は製品のコストパフォーマンスを高めるため、生産設備の開発を精力的に行うようになった。この間、生産された電子製品の中で最も優れていたのはVLSIであった。

Phase 4: 1995-present

マイクロアセンブリ、高密度アセンブリ、3次元アセンブリ技術が急速に発展している。報告によると、スルーホール組立技術を用いた世界の電子製品は年11%の割合で減少しており、SMTパッチを用いた電子製品は年8%の割合で増加している。

Technology development has always been the mainstream of the world. Therefore, FS Technology has always advocated advancing with the times, whether that is committing to creating automated, intelligent and flexible production lines, or using the latest SMT assembly technology to serve customers. As someone in the electronics manufacturing industry, it is very important to understand the development history of PCBあなたのビジネスが正しい変化の方向性を見出すための一助となるものです。

電子機器製造業でSMTが支持される理由

As mentioned above, SMT has gradually replaced THT, so what advantages does this technology have, and why do turnkey PCB assembly manufacturers prefer it? FS Technology will take you through the advantages of this technology.

高い組み立て密度

Compared with traditional DIP technology, SMD components can make the assembly area and mass smaller. The PCBA product assembled using SMT is 40% of the volume of the DIP and only 35% of the mass. DIP components are mounted on a 2.54 mm grid, while SMD can perform better. In order to meet customers’ requirements for smaller electronic products, FS Technology’s SMT technology is becoming more and more mature. Our surface mount assembly component grid has grown from 1.27 mm to the current 0.63 mm grid, and some special components can even be mounted on a 0.5 mm grid.

より信頼性の高い技術

SMD部品は小型軽量であるため、耐衝撃性、信頼性が高くなります。SMT組立製品を生産する際、FSテクノロジーは7つの全自動生産ラインを使用しています。生産ラインには厳しい品質管理基準があり、一般的なハンダ接合不良率は100万分の10以下です。スルーホール部品のウェーブソルダー技術は一桁低く、SMTで組み立てた電子製品の平均MTBFは25万時間で、これが電子製品の90%がSMTプロセスを採用する主な理由である。

良好な高周波特性

SMD部品はプラグインとは異なります。一般的にダイレクトパッチ溶接ではリード線を使用しないか短いリード線を使用するため、回路のインダクタンスや大容量の容量、抵抗への影響を大幅に軽減することができます。プロジェクトでは、PCBA基板のMHzが非常に重要であり、パッチ方式を用いることで回路の周波数を上げることができる。SMDとTHTを比較した結果、FSテクノロジーは、表面実装技術で設計した回路の最大周波数が3GHzに達するのに対し、スルーホール技術の最大周波数は500MHzに過ぎないことを突き止めた。SMDはその高い周波数特性により、回路基板の伝送時間を短縮することができ、これはコンピューターなど最も伝送時間を必要とする電子製品にとって非常に重要なことです。

組立プロジェクトのコスト削減

PCBA基板に開ける穴の数を減らすことができる
基板デバッグのコストと時間の削減
梱包、輸送、保管のコスト削減
チップ抵抗器の価格はスルーホール抵抗器並み

生産の自動化が容易

Surface mount is a technology that makes it easier to automate mass production. Taking FS Technology as an example, we have 7 SMT lines, all of which use automated SMT equipment to pick up and mount SMD部品 with vacuum nozzles. Due to the smaller size of these vacuum nozzles, the assembly equipment can be assembled with higher precision. In fact, most PCBA companies are now produced by automated placement. If a turnkey PCB assembly company wants to use THT technology for large-scale automated production, it needs to expand the area of the PCB bare board to at least 140%.

表面実装技術の意義を包括的に理解する必要があるのなら、SMTのメリットだけでなく、デメリットも知っておく必要があるのです。

Disadvantages of electronic SMT technology

The nominal value of SMD electronic components is not easy to see;
Difficulty repairing PCBAs assembled using SMT;
Difficulty replacing components on PCBA;
Poor Coefficient of Expansion Consistency of SMD components;
Component leakage, component misalignment and component damage are prone to occur during the assembly process;

In order to deal with these shortcomings, FS Technology recommends these solutions for you:

SMD部品の良好な濡れ性を維持する
Maintain solder continuity on the surface of the solder joint. The closer to the edge of the solder joint, the thinner the solder layer will be.
Ensure a small edge line of the pad, so the contact angle between the SMT device and the pad is less than 30 degrees.
No contamination such as solder mask is allowed on the surface of the metal to be welded.
The solder joint solder layer should be moderately applied, avoid excessively too much or too little amounts.
The solder spot position must be accurate and the end/pin of the PCB component should be in the center of the pad. The width and length direction should not exceed the phenomenon.
はんだ接合面は連続的で平滑であること、リフロー溶接で形成されたはんだ接合部は明るい外観であることが必要です。

How to Choose Manufacturers for PCBA SMT Assembly?

The above covers almost everything that electronics enthusiasts may be interested in, but if you are a PCBA engineer and are urgently find PCBA factory to provide you with SMT assembly services, then the following content is what you have to see!

An engineer put much effort into the printed circuit board project before the assembly. Hence, it’s crucial to choose a better SMT vendor for the assembly. Selecting a company to work with can be challenging because there are so many options, and this choice is so important. If you need to choose a PCB assembly firm, how can you determine the ideal fit for your project? To make it easy for you, we are listing the services that should be available to the customers by the company:

The manufacturing facility with cutting-edge machinery and tools, making it capable of meeting the difficulties posed by constructing even the most complicated PCBs.
Engineers with years of experience who are ready to assist you throughout the whole procedure and ensure that everything runs efficiently.
Materials of the highest quality – The firm only utilizes SMT SMD components of the highest quality to ensure that the boards’ quality can match and surpass the user’s expectations.
Delivery within the specified time frame. It indicates that the company can feasibly fulfill mass production orders in the shortest amount of time. The completion of the manufacturing within the allotted time is something the firm assures.
Prices are reasonable; the clientele’s satisfaction is the organization’s primary focus. Because of this, you may anticipate reasonable costs suitable for any financial plan.

まとめる

No matter what you want to use a printed circuit board for, it would be best to fabricate one that is reliable and has a high-performance level during its lifetime. If you have a reliable SMT electronics manufacturer on your team, you should be easily able to accomplish this goal.

Even though it contains more 電子部品, assembling a printed circuit board is just as important as designing and making it. As you can see from this article, SMT assembly plays a significant role in almost all contemporary forms of electronic product design. If your PCB design still uses the through-hole method, SMT assembly could help your product move forward. Therefore, make sure you work with a trustworthy and knowledgeable assembly partner to avoid any problems that might arise with SMT assembly.

The above article sums up FS Technology’s entire explanation of what SMT really represents in electronic products and the electronic field. From here, FS Technology will continue to update and produce more articles regarding SMT in our blog, so stay tuned.

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