Common components, package, size, surface treatment, etc.

Reference: https://www.bilibili.com/read/cv11024927?from=search&spm_id_from=333.337.0.0 Reference:
https://www.bilibili.com/read/cv18413169?from=search&spm_id_from=333.337.0.0

Through Hole Technology (THT) and Surface Mount Technology (SMT)

• The English full name of through-hole plug-in technology is Through Hole Technology, abbreviation: THT. Through-hole technology is to insert components into the circuit board and then solder them firmly with solder.
  

• SMT is Surface Mount Technology (Surface Mount Technology) (Surface Mounting Technology abbreviation), known as surface mount or surface mount technology, is currently the most popular technology and process in the electronics assembly industry.

• It installs surface mount components (SMC/SMD for short, chip components in Chinese) packaged in a matrix arrangement without leads or short leads or balls on the surface of a printed circuit board (PCB) or other substrates. On the surface, it is a circuit assembly technology that is soldered and assembled by methods such as reflow soldering or dip soldering.

package type

Component packaging plays the role of installation, fixing, sealing, chip protection and enhancing electrothermal performance. At the same time, the contacts on the chip are connected to the pins of the package shell with wires, and these pins are connected to other devices through the wires on the printed circuit board, so as to realize the connection between the internal chip and the external circuit.

Therefore, the chip must be isolated from the outside world to prevent impurities in the air from corroding the chip circuit and causing electrical performance degradation. Moreover, the packaged chip is also easier to install and transport. Since the quality of the package directly affects the performance of the chip itself and the design and manufacture of the PCB connected to it, the packaging technology is very important.

An important indicator to measure whether a chip packaging technology is advanced or not is: the ratio of chip area to package area, the closer this ratio is to 1, the better.

The main factors to consider when packaging:

• The ratio of chip area to package area should be as close to 1:1 as possible to improve packaging efficiency.

• The pins should be as short as possible to reduce delay, and the distance between pins should be as far as possible to ensure non-interference and improve performance.

• Based on heat dissipation requirements, the thinner the package, the better.

Encapsulation has generally gone through the following development process:

• structural aspects. TO→DIP→PLCC→QFP→BGA→CSP.

• Material aspect. Metal, ceramic → ceramic, plastic → plastic.

• pin shape. Long lead in-line → short lead or leadless mounting → ball bump.

• Assembly method. Through-hole → surface mount → direct mount.

QFP Package (Small Cube/Quad Gull Wing)

QFP is the abbreviation of "Quad Flat Package", which is a small square planar package. QFP package was frequently used on early graphics cards, but there are few QFP package video memory with a speed above 4ns. Due to process and performance problems, it has been gradually replaced by TSOP-II and BGA. The QFP package has pins around the particles, which are quite obvious to identify. Four side pinned flat pack. One of the surface mount packages, the pins are led out from the four sides in a gull-wing (L) shape.

There are three kinds of substrates: ceramic, metal and plastic. In terms of quantity, plastic packaging accounts for the vast majority. When the material is not specified, it is plastic QFP in most cases. Plastic QFP is the most popular multi-pin LSI package. It is not only used for digital logic LSI circuits such as microprocessors and gate arrays, but also for analog LSI circuits such as VTR signal processing and audio signal processing.

The center distance of the pins has various specifications such as 1.0mm, 0.8mm, 0.65mm, 0.5mm, 0.4mm, 0.3mm, etc., and the maximum number of pins in the 0.65mm center distance specification is 304.

QFN Package (Quad Flat No Leads)

QFN（Quad Flat No-leads Package，Quad Flat No Lead Package), one of the surface mount packages. It is worth noting that the QFN package is completely different from the LCC package. The LCC still has extension pins, but the pins are bent to the bottom, while the QFN package does not have any extension pins at all. QFN is a name stipulated by the Japan Electron Machinery Industry Association.

DIP package (dual in-line plug)

DIP is the abbreviation of "Double In-line Package" in English, namelyDual Inline Package.

One of the plug-in packages, the pins are drawn from both sides of the package, and the packaging materials are plastic and ceramic. DIP is the most popular plug-in package, and its application range includes standard logic IC, memory LSI, microcomputer circuit, etc.

SOP/SOIC package (small outline package, two rows of pins)

SOP is the abbreviation of Small Outline Package in English, that is, small outline package.

SOP packaging technology was successfully developed by Philips from 1968 to 1969, and then gradually derived:

• SOJ, J-lead small outline package

• TSOP, Thin Small Outline Package

• VSOP, Very Small Outline Package

• SSOP, reduced SOP

• TSSOP, Thin Miniature SOP

• SOT, Small Outline Transistor

• SOIC, Small Outline Integrated Circuit

PLCC package (pin J shape)

PLCC is the abbreviation of "Plastic Leaded Chip Carrier" in English, that is, plastic J-shaped lead chip package.

PLCC packaging method, the shape is square, 32-pin package, there are pins around, and the overall size is much smaller than the DIP package. The PLCC package is suitable for installing and wiring on the PCB with SMT surface mount technology, and has the advantages of small size and high reliability.

TQFP package (quad flat)

TQFP is the abbreviation of "Thin Quad Flat Package" in English, that is, thin plastic four-corner flat package. The quad flat pack process can effectively use the space, thereby reducing the requirement on the space size of the printed circuit board.

Due to the reduced height and volume, this packaging process is ideal for space-critical applications such as PCMCIA cards and networking devices. Almost all of ALTERA's CPLD/FPGA has TQFP package.

PQFP package (four-pin flat / many pins)

PQFP is the abbreviation of "Plastic Quad Flat Package" in English, that is, plastic quadrangular flat package.

Between the chip pins of the PQFP packageThe distance is small and the pins are very thin. Generally large-scale or ultra-large-scale integrated circuits adopt this packaging form, and itsThe number of pins is generally more than 100。

TSOP package (only two rows of pins)

TSOP is the abbreviation of "Thin Small Outline Package" in English, that is, thin and small size package. A typical feature of TSOP memory packaging technology is to make pins around the packaged chip. TSOP is suitable for mounting wiring on PCB with SMT (Surface Mount) technology. look atonly two rowspin.

TSOP package appearance, parasitic parameters (when the current changes greatly, causing output voltage disturbance) are reduced, suitable for high frequency applications, easy to operate, and relatively high reliability.

BGA Package (Ball Grid Array)

BGA is the abbreviation of "Ball Grid Array Package" in English, namelyBall Grid Array Package. In the 1990s, with the advancement of technology, the integration of chips continued to increase, the number of I/O pins increased sharply, power consumption also increased, and the requirements for integrated circuit packaging became more stringent. In order to meet the needs of development, BGA packaging began to be used in production.

The memory packaged with BGA technology can increase the memory capacity by two to three times while maintaining the same volume. Compared with TSOP, BGA has smaller volume, better heat dissipation and electrical performance. BGA packaging technology has greatly improved the storage capacity per square inch. Under the same capacity, the volume of memory products using BGA packaging technology is only one-third of that of TSOP packaging. In addition, compared with the traditional TSOP packaging method, the BGA packaging method has a faster and more effective heat dissipation method.

The I/O terminals of the BGA package are distributed under the package in the form of circular or columnar solder joints in an array. The advantage of BGA technology is that although the number of I/O pins has increased, the pin spacing has not decreased but increased, thus Increased assembly yield. Although its power consumption increases, BGA can be soldered with controlled collapse chip method, which can improve its electrothermal performance. Compared with the previous packaging technology, the thickness and weight are reduced; the parasitic parameters are reduced, the signal transmission delay is small, and the frequency of use is greatly increased; the assembly can be coplanar welding, and the reliability is high.

TinyBGA package

When it comes to BGA packaging, we must mention Kingmax's patented TinyBGA technology. The English full name of TinyBGA is "Tiny Ball Grid". It belongs to a branch of BGA packaging technology and was successfully developed by Kingmax in August 1998. The ratio of the chip area to the package area is not less than 1:1.14, which can increase the memory capacity by 2 to 3 times without changing the volume of the memory. Compared with TSOP package products, it has smaller volume, better heat dissipation performance and electrical performance.

The volume of memory products using TinyBGA packaging technology is only 1/3 of that of TSOP packaging under the same capacity. The pins of TSOP package memory are drawn from the periphery of the chip, while the pins of TinyBGA are drawn from the center of the chip. This method effectively shortens the transmission distance of the signal, and the length of the signal transmission line is only 1/4 of the traditional TSOP technology, so the attenuation of the signal is also reduced. This not only greatly improves the anti-interference and anti-noise performance of the chip, but also improves the electrical performance. Chips in TinyBGA package can resist FSB up to 300MHz, while traditional TSOP package technology can only resist FSB up to 150MHz.

The thickness of the TinyBGA packaged memory is also thinner (the package height is less than 0.8mm), and the effective heat dissipation path from the metal substrate to the radiator is only 0.36mm. Therefore, TinyBGA memory has higher heat conduction efficiency and is very suitable for long-running systems with excellent stability.

MELF package (cylindrical)

MELF is a cylindrical metal electrode leadless interface technology. The word "MELF" comes from the English name "Metal Electrode Leadless Face" of this technology.

MELF packaging technology was produced in the late 1980s. Its appearance has solved some problems that have plagued the industry for a long time. One of the most notable is that in the past, glass diodes were extremely fragile and required extra care during use. MELF diodes perfectly solve this problem and greatly improve efficiency.

MELF is mostly used in surface mount diodes, resistors, capacitors and inductors to meet the requirements of surface mount technology (also known as SMT technology: Surface-Mount Technology). MELF electronic components can be directly placed on the printed circuit board for soldering or mounting, replacing traditional jack electronic components with its high efficiency and stability. These components have small size, high precision, good heat dissipation and resistance to temperature changes (from -55 degrees to +155 degrees), which make the resulting circuit boards especially suitable for use in harsh working environments.

The special shape of the MELF element makes it difficult to operate, especially because of its small size (the length of the small stick-type diode is less than 2mm, and the diameter is less than 1mm). Printed circuit boards or countertops rolling to the floor. For this reason, some people jokingly call them MELF (Most Ended up Lying on the Floor, "most of them fell to the ground"). Despite their inconveniences, MELFs are widely adopted in high-reliability, high-precision applications. Some of their obvious advantages, such as low damage rate and precision under specified conditions, ability to withstand moisture and corrosion, long-term stability and safety in ultra-high and low-temperature environments, and The unique homogeneity and the convenience of no lead constraints during mounting make it the best choice among surface mount electronic components in terms of function, structure and electrical characteristics.

Attached picture

• MELF diodes:
  
• MELF resistance:
  

PTH (Through Hole In-line Components)

SMD (Surface Mount Components)

SMT (Surface Mount Technology) is essentially a technical method of arranging components onto a circuit board, while SMD (Surface Mount Devices) are actual components mounted on a circuit board according to specific components.

Chip-R Chip Resistors

SMD fixed resistors are also called chip fixed resistors, referred to as chip resistors or chip resistors. English Chip Fixed Resistor, referred to as Chip-R and SMD Risistor, is the most widely used and widely used component in electronic circuits.

PTH, NPTH, VIA in PCB through holes

It can be observed that there are many large and small holes in the circuit board, and it will be found that there are many densely packed small holes, and each hole is designed for its purpose. These holes can be roughly divided into two types: PTH (Platating Through Hole, electroplating through hole) and NPTH (Non Plating Through Hole, non-plating through hole). Here we say "through hole" because this kind of hole is really from the circuit board. One side penetrates to the other side. In fact, in addition to through holes, there are other holes in the circuit board that do not penetrate the circuit board.

Explanation of PCB terms: through hole, blind hole, buried hole.

1. How to distinguish between PTH and NPTH?

It can be judged by looking at the bright plating traces on the hole wall. The holes with plating traces are PTH, and the holes without plating traces are NPTH. As shown below:

2. What is the purpose of NPTH?

It is found that the hole diameter of NPTH is usually larger than that of PTH, because most of NPTH are used as locking screws, and some are used to install some external connectors. In addition, some will be used as the positioning of the test fixture on the edge of the board.

3. What is the purpose of PTH? And what is Via?

Generally, the PTH holes on the circuit board have two uses, one is used to weld the feet of traditional DIP parts, the diameter of these holes must be larger than the diameter of the welding feet of the parts, so that the parts can be inserted into the holes.

Another relatively small PTH, usually called via (via hole), is used to connect and conduct the copper foil lines between two or more layers of the circuit board (PCB), because the PCB is made of Many copper foil layers are stacked and accumulated, and an insulating layer is laid between each layer of copper foil (copper), which means that the copper foil layers cannot communicate with each other, and the signal connection is via via. That's why it is called "via hole" in Chinese. Via is completely invisible from the outside. Because the purpose of via is to connect copper foils of different layers, electroplating is required to conduct, so via is also a kind of PTH.

Component size table

There are 9 common packages for chip resistors, which are represented by two size codes. A size code is an EIA (American Electronics Industries Association) code represented by 4 digits. The first two digits and the last two digits represent the length and width of the resistor respectively, in inches. The 0603 package we often say refers to the imperial code . The other is the metric code, which is also represented by 4 digits, and its unit is millimeters. The following table lists the relationship between inch and metric and detailed dimensions of chip resistor packages.

The metric system is about 2~3 times the size of the imperial system

PCB surface treatment method (HASL hot air leveling/OSP anti-oxidation/ENIG chemical immersion gold)

At present, the PCB surface treatment processes of domestic circuit board manufacturers include: spray tin (HASL, hot air solder leveling hot air leveling), immersion tin, immersion silver, OSP (anti-oxidation), chemical immersion gold (ENIG), electroplating gold, etc., of course, special There will also be some special PCB circuit board surface treatment processes in the application. Different PCB surface treatment processes have a greater impact on the final PCB processing quotation, and different PCB surface treatment processes will have different charges.

• HASL (Hot Air Solder Leveling)
• OSP (Organic Solder Preserve)
• ENIG (Electroless Nickel Immersion Gold)
• ENIPIG (Electroless Nickel Immersion Palladium Gold)
• ENEPIG (Electroless Nickel Palladium Immersion Gold)
• ImmAg (immersion silver)
• ImmSn (immersion tin)
• Nickel sulfamate, hard gold sulfamate or soft gold sulfamate (electrolytic nickel, electrolytic gold)
• SnPb (63 tin, 37 lead)
• LF (lead-free)

1. Hot air leveling (HASL/LFHASL)

Scope of application: The tin-spraying process used to play a dominant role in the PCB surface treatment process, especially for larger-sized components and larger-spaced wires, it is a very good process.

Advantages: lower price, good welding performance. In a PCB with a higher density, the flatness of the tin spraying process will affect the subsequent assembly; therefore, the HDI board generally does not use the tin spraying process.

Disadvantages: It is not suitable for soldering pins with fine gaps and components that are too small, because the surface flatness of the tin plate is poor. Tin balls are easy to be produced during PCB processing, and short circuits are more likely to be caused by fine-gap pin components. When used in a double-sided SMT process, this is because the second side has undergone a high-temperature reflow soldering, and it is very easy to remelt the tin spray to produce tin beads or similar water drops that are affected by gravity and become spherical tin spots that drop, causing surface It is more uneven and affects welding problems.

Method: Coating molten tin-lead solder on the surface of the PCB and leveling (blowing) it with heated compressed air to form a coating that resists copper oxidation and provides good solderability. During hot air leveling, solder and copper form a copper-tin metal compound at the junction, and its thickness is about 1-2mil;

2. Organic anti-oxidation (OSP)

Scope of application: It is estimated that about 25%-30% of PCBs currently use the OSP process, and the proportion has been rising (it is likely that the OSP process has now surpassed tin spraying and ranks first). The OSP process can be used on low-tech PCBs or high-tech PCBs, such as PCBs for single-sided TVs and boards for high-density chip packaging. For BGA, there are many applications of OSP. If the PCB has no surface connection functional requirements or storage period limitations, the OSP process will be the most ideal surface treatment process.

Advantages: It has all the advantages of bare copper plate welding, and the expired (three months) board can also be resurfaced, but usually only once.

Cons: Vulnerable to acid and humidity. When used for secondary reflow soldering, it must be completed within a certain period of time, and usually the effect of the second reflow soldering will be relatively poor. If the storage time exceeds three months, it must be resurfaced. Use within 24 hours after opening the package. OSP is an insulating layer, so the test point must be printed with solder paste to remove the original OSP layer in order to contact the pin for electrical testing.

Method: On the clean bare copper surface, a layer of organic film is grown chemically. This layer of film has anti-oxidation, thermal shock resistance, and moisture resistance. It is used to protect the copper surface from rusting (oxidation or vulcanization, etc.) in a normal environment; Quickly removed by flux to facilitate soldering;

3. Electroless Nickel Gold

Scope of application: It is mainly used on boards with connection functional requirements and long storage period on the surface, such as the keypad area of ​​mobile phones, the edge connection area of ​​the router shell and the electrical contact area of ​​the elastic connection of the chip processor. Due to the flatness of the tin-spraying process and the removal of flux in the OSP process, immersion gold was widely used in the 1990s; later, due to the appearance of black plates and brittle nickel-phosphorus alloys, the application of immersion gold was reduced , but at present almost every high-tech circuit board manufacturer has immersion gold wires.

Considering that the solder joint becomes brittle when the copper-tin intermetallics are removed, many problems will arise at the relatively brittle nickel-tin intermetallics. Therefore, almost all portable electronic products (such as mobile phones) use copper-tin intermetallic compound solder joints formed by OSP, immersion silver or immersion tin, and immersion gold is used to form the key area, contact area and EMI shielding area, which is the so-called selectivity. Immersion gold craft. It is estimated that about 10%-20% of PCBs currently use electroless nickel/immersion gold processes.

Advantages: It is not easy to oxidize, can be stored for a long time, has a flat surface, and is suitable for welding fine-gap pins and components with small solder joints. The first choice for PCB boards with buttons (such as mobile phone boards). It can be reflowed many times without degrading its solderability. It can be used as the base material for COB (ChipOnBoard) wiring.

Disadvantages: high cost, poor welding strength, because of the use of electroless nickel plating process, it is easy to have the problem of black plate. The nickel layer oxidizes over time, and long-term reliability is an issue.

Method: Wrap a thick layer of nickel-gold alloy with good electrical properties on the copper surface and protect the PCB for a long time. Unlike OSP, which is only used as an anti-rust barrier layer, it can be useful and achieve good electrical performance during the long-term use of the PCB. In addition, it also has the tolerance to the environment that other surface treatment processes do not have;

4. Chemical immersion silver

Scope of application: immersion silver is cheaper than immersion gold. If the PCB has connection functional requirements and needs to reduce costs, immersion silver is a good choice; plus immersion silver has good flatness and contact, then immersion silver technology should be selected . Immersion silver is widely used in communication products, automobiles, and computer peripherals, and it is also used in high-speed signal design.

Because immersion silver has good electrical properties that cannot be matched by other surface treatments, it can also be used in high-frequency signals. EMS recommends the immersion silver process because it is easy to assemble and has better inspectability. However, due to defects such as tarnish and solder joint voids in immersion silver, its growth has been slow (but not declining). It is estimated that about 10%-15% of PCBs currently use immersion silver technology.

Features: Between OSP and electroless nickel/immersion gold, the process is relatively simple and fast. Exposure to heat, humidity and contamination will still provide very good electrical properties and maintain good solderability, but will tarnish. This is because there is no nickel under the silver layer, so immersion silver does not have all the good physical strength of electroless nickel/immersion gold;

5. Electroplated nickel gold

Scope of application: Nickel plating is used as the substrate coating of precious metals and base metals on PCBs. For some single-sided printed boards, it is often used as a surface layer. For some surfaces with heavy load wear, such as switch contacts, contacts or plug gold, using nickel as the gold substrate plating can greatly improve wear resistance.

When used as a barrier layer, nickel is effective in preventing diffusion between copper and other metals. Dumb nickel/gold combination coating is often used as an anti-etching metal coating, and can meet the requirements of thermocompression welding and brazing. Only nickel can be used as an anti-corrosion coating containing ammonia-based etchant, and PCBs that do not require hot-press welding and require a bright coating usually use light nickel/gold coating. The thickness of the nickel coating is generally not less than 2.5 microns, usually 4-5 microns.

Advantages: It can greatly improve wear resistance and effectively prevent the diffusion between copper and other metals.

Disadvantages: the color is not bright enough, and the appearance is slightly inferior to heavy gold.

Method: Electroplate a layer of nickel on the conductor on the surface of the PCB, and then electroplate a layer of gold. The nickel plating is mainly to prevent the diffusion between gold and copper. There are two types of electroplated nickel gold: soft gold (pure gold, gold does not look bright) and hard gold (smooth and hard surface, wear-resistant, containing cobalt and other elements, the surface looks brighter). Soft gold is mainly used for making gold wires in chip packaging; hard gold is mainly used for electrical interconnections (such as gold fingers) at non-welding places.

6. Immersion tin

Immersion tin has been introduced into the surface treatment process for nearly ten years, and the emergence of this process is the result of the requirements of production automation. Immersion tin does not bring any new elements into the welding place, which is especially suitable for communication backplanes. Tin will lose its solderability outside the storage period of the board, so immersion tin requires better storage conditions. In addition, the immersion tin process is restricted due to the presence of carcinogens. It is estimated that about 5%-10% of PCBs currently use the immersion tin process.

7. PCB hybrid surface treatment process

Choose two or more surface treatment methods for surface treatment. The common methods are: immersion nickel gold + anti-oxidation, electroplating nickel gold + immersion nickel gold, electroplating nickel gold + hot air leveling, immersion nickel gold + hot air leveling .