Dip Soldering and SMD Solered Devices

/0 Kommentarer/i /af

Dip Soldering and SMD Solered Devices

Dip soldering and smd soldered devices are two different processing methods that are used to assemble electronic devices. Both methods use a reflow process that involves a gradual heating of the solder paste. When the reflow process is successful, the melted solder paste effectively bonds the mounted components to the PCB, creating a stable electrical connection. The two methods share several common characteristics.

Asymmetrical wave soldering

Asymmetrical wave soldering is the process of forming a ring of solder that surrounds the part and is able to separate it from the surrounding air. It also creates a barrier between the solder and oxygen. This method of soldering is easy and versatile, but it can present significant challenges, particularly when using surface mount devices.

The wave soldering process is one of the most commonly used soldering methods. It is a bulk soldering process that allows manufacturers to mass-produce many circuit boards quickly. The circuit boards are passed over the molten solder, which is created by a pump in a pan. The wave of solder then adheres to the components of the PCB. During the process, the circuit board must be cooled and blown to prevent the solder from contaminating the PCB.

Flux barrier

Flux is a liquid which allows molten solder to flow and removes oxides from the surface. There are three types of flux. These include water-based, alcohol-based, and solvent-based. During the soldering process, the board must be preheated in order to activate the flux. Once the soldering process has completed, the flux must be removed using solvent-based or water-based removers.

A high-quality flux is critical to achieving the desired results during the soldering process. A high-quality flux will improve the wetting and bonding properties of the solder. However, a high-activation flux may increase the risk of oxidisation, which is not always desirable.

Cold joints

In cold soldering, the alloy does not fully melt or reflow. This can have serious consequences in an electronic device. This can affect the conductivity of the solder and result in a failed circuit. To test cold solder joints, connect a multimeter to the terminals. If the multimeter indicates a resistance over 1000 ohms, the cold joint has failed.

Soldering a PCB requires good solder joints, which ensure the function of the product. Generally, a good solder joint will be smooth, bright and contain an outline of the soldered wire. A poor solder joint will cause the PCB to short out and cause damage to the device.

Adding metal to PCBs

Adding metal to PCBs with dip or smd soldering involves adding a filler metal to the PCB before soldering. Soft soldering is the most common method for attaching small components to the PCB. Unlike traditional solder, soft soldering does not melt the component, as the solder will not be able to adhere to the oxidized surface. Instead, a filler metal, usually a tin-lead alloy, is added.

Before soldering the component, it is important to prepare the soldering iron to 400degC. This heat must be high enough to melt the solder on the tip. It is helpful to tin the tip before soldering to help transfer heat. In addition, it helps to keep the components organized so that soldering will not be stressful.

Manual vs automated wave soldering

Wave soldering equipment comes in various forms, including robotic, manual, and immersion selective systems. There are several advantages and disadvantages to each type. You should purchase the one that best suits your operation’s needs. For instance, a lean operation should consider purchasing the simplest model. However, you should also consider the cost of the equipment. In most cases, manual wave soldering equipment will cost less than an automated machine.

Manual soldering is slower than automated wave soldering and is prone to human error. However, selective soldering eliminates these problems by allowing the operator to program exact spots for each component. Furthermore, selective soldering does not require glue. Additionally, it does not require expensive wave solder pallets and is cost-effective.

Problems with SMD soldering

Soldering problems can occur for a number of reasons. One common cause is the wrong paste template when using solder flux or the wrong assembling feeder setting. Other problems include insufficient solder and bad solderability of the parts or pads. These errors can lead to the welding point to form unexpected shapes. Solder balls, solder icicles, and holes can also result from improper soldering.

Another common reason for non-wetting solder joints is improper cleaning. Insufficient wetting means that the solder did not adhere intimately to the component. As a result, the components are not connected and may fall off.

Soldering Methods of PCB Chip Package and Processes

/0 Kommentarer/i /af

Soldering Methods of PCB Chip Package and Processes

Lodning er en kritisk del af en PCB-chippakke. Loddeprocesser involverer en kombination af teknikker, herunder fokuseret IR, konvektion og ikke-fokuseret IR. Hver metode indebærer en gradvis opvarmning af pakken efterfulgt af afkøling af hele samlingen.

Soldering process

Soldering is the process of joining solder balls and other solder materials to PCB chip packages. This process is done using two types of methods. The convection method and the reflow process. The first type involves a heating process using a flux that forms a liquid. In both processes, the peak temperature is controlled. However, the reflow process must be performed with enough caution to prevent the formation of brittle solder joints.

Depending on the components used in the PCB, the soldering process can be either soft or hard. The type of soldering iron used must be suitable for the kind of components. The process should be done by a PCB assembly and manufacturing services provider who has extensive experience with PCBs and knows the exact way to implement each process.

Dimensions of solder pads

The dimensions of solder pads on a PCB chip package are critical to ensure that the component’s performance is optimized. This is especially true in the high-frequency area where component placement and soldering techniques may not be as accurate as required. The IPC-SM-782 standard is a valuable reference document for optimum component placement and soldering. However, blindly following the document’s requirements may result in suboptimal high-frequency performance or high-voltage problems. In order to avoid these problems, PCBA123 recommends that solder pads be kept small and in a single row.

In addition to pad sizes, other factors such as component placement and alignment are also important. Using incorrectly sized pads can result in electrical problems, as well as limiting the manufacturability of the board. Therefore, it is important to follow the industry’s recommended PCB pad sizes and shapes.

Fluxing

Fluxing is an important component of the soldering process. It removes metallic impurities and oxides from the soldering surface to present a clean surface for high-integrity solder joints. The flux residue is removed in a final cleaning step, which will depend on the type of flux used.

There are many different fluxes used for the soldering process. They range from resin to rosin-based. Each of them serves a different purpose and is categorized by activity level. The activity level of the flux solution is usually listed as L (low activity or halide-free) or M (medium activity, 0 to 2% halide), or H (high activity, up to 3% halide content).

One of the most common defects is mid-chip solder balls. A common solution for this problem is to alter the stencil design. Other methods include using nitrogen during the soldering process. This prevents the solder from vaporizing, allowing the paste to form a superior bond. Finally, a washing step helps remove any grit and chemical residue from the board.

Inspection

There are several different types of testing tools that can be used to inspect PCB chip packages. Some of them include in-circuit testing, which uses probes that connect to different test points on the PCB. These probes can detect poor soldering or component failures. They can also measure voltage levels and resistance.

Improper soldering can cause problems with the circuitry of the PCB. Open circuits occur when solder does not reach the pads properly or when solder climbs up on the surface of the component. When this happens, the connections will not be complete, and the components will fail to work correctly. Often, this can be avoided by carefully cleaning the holes and ensuring that molten solder covers the leads evenly. Otherwise, excess or incomplete solder coverage can cause the leads to dewet or become non-wetting. To prevent dewetting, use high quality solder and quality assembly equipment.

Another common way to detect defect on PCBs is through Automated Optical Inspection (AOI). This technology uses cameras to take HD pictures of the PCB. It then compares these images with pre-programmed parameters to identify the components’ defect status. If any defect is detected, the machine will mark it accordingly. AOI equipment is generally user-friendly, with simple operations and programming. However, AOI may not be useful for structural inspections, or for PCBs with large numbers of components.

Rectification

The soldering processes used in the manufacture of electronic products should adhere to certain standards and guidelines. In general, a solder mask should be at least 75% thick to guarantee reliable solder joints. Solder pastes should be applied onto PCBs directly, not screen-printed. It is best to use a stencil and jig suited to a particular package type. These stencils use a metal squeegee blade to apply solder paste onto a package’s surface.

There are several benefits to using a wave soldering process instead of the traditional flux spraying method. The wave solder process uses a mechanical wave soldering process to adhere parts to PCBs with high levels of stability. This method is more expensive, but provides a safe and reliable method of fixing electronic components.

Introduction About Single Sided and Double Sided SMT Assembly

/0 Kommentarer/i /af

Introduction About Single-Sided and Double-Sided SMT Assembly

Single-sided and double-sided SMT assemblies differ in terms of component density. Single-sided SMT assembly has a higher density than double-sided SMT assembly and requires a higher amount of heat to process. Most assemblers process the higher-density side first. This minimizes the risk of components falling out during the heating process. Both sides of the reflow assembly process require the addition of SMT adhesive to hold the components in place during the heating operation.

FR4 PCB

Single-sided PCBs are the most common. In a single-sided board, all the components are located on one side of the board, and assembly is only needed on that side. Double-sided boards have traces on both sides of the board, which reduces their footprint. Double-sided boards also offer better heat dissipation. The manufacturing process for double-sided boards is different than for single-sided PCBs. During the double-sided process, copper is removed from the double-sided board and then reinserted after an etching process.

Single-sided PCBs are also easier to manufacture and less expensive. Manufacturing a single-sided PCB includes several stages, including cutting, drilling holes, circuit treatment, solder resist, and text printing. Single-sided PCBs also undergo electrical measurements, surface treatment, and AOI.

PI copper-clad board

The PI copper-clad board single-sided and double-sided smt assembly process involves the use of a polyimide cover film to laminate copper on one side of the PCB. The copper-clad board is then pressed into position by an adhesive glue that opens at a specific position. Afterwards, the copper-clad board is patterned with anti-welding resistance and the part guide hole is punched.

A single-sided flexible PCB is composed of a PI copper-clad board with one conductor layer, usually rolled copper foil. This flexible circuit is covered with a protective film after the circuit is completed. A single-sided flexible PCB can be manufactured with or without a cover layer, which acts as a protective barrier to protect the circuit. Single-sided PCBs have only one layer of conductors, which is why they are often used in portable products.

FR4

FR4 is a grade of epoxy resin that is commonly used in PCB fabrication. This material offers excellent heat and flame resistance. The FR4 material has a high glass transition temperature, which is crucial for high-speed applications. Its mechanical properties include tensile and shear strength. Dimensional stability is tested to ensure the material does not change shape or lose its strength in various working environments.

FR4 single-sided and double-stacked multi-layer boards consist of an FR4 insulating core and a thin copper coating on the bottom. During manufacturing, through-hole components mounted on the component side of the substrate with leads running through to copper tracks or pads on the bottom side. In contrast, surface-mounted components mount directly on the solder side. While they are very similar in structure and construction, the primary difference is in the placement of the conductors.

FR6

Surface Mount Technology (SMT) assembly is an efficient way to attach electronic components to printed circuit boards without the need for holes. This type of technology is suitable for both leaded and non-leaded components. With the double-sided SMT technique, the printed circuit board (PCB) has two conductive layers – one on the top and one on the bottom. The copper covering on both sides of the board acts as a current-carrying material and helps in the attachment of components to the PCB.

For single-sided boards, it is easy to use simple support pillars. For double-sided boards, additional support is required. The free area around the board should be at least 10 mm.

FR8

The process of FR8 single-sided and double smt assembly is similar to the general assembly process with a few differences. Both processes use adhesive and solder paste. They are followed by cleaning, inspection, and testing. The finished product must meet the specifications specified by the designer.

Single-sided boards are more common and have a smaller footprint. However, double-sided boards reduce space requirements and maximize heat dissipation. During the etching process, copper is removed from the double-sided side. It is reinserted after the process.

How to Do a PCB Impedance Calculation Model

/0 Kommentarer/i /af

How to Do a PCB Impedance Calculation Model

Using a Smith chart

The Smith chart is a useful tool when you want to determine the impedance of a circuit. It is a visual representation of the complex resistance versus frequency of an electrical circuit. It also shows the locus of impedance versus frequency, which is necessary for stability analysis and oscillation avoidance. Many PCs have the ability to display impedance values numerically, but the Smith chart helps you visualize the possibilities.

The Smith chart can be used to evaluate the signal path between a PC board’s contact pads and an electronic device. This device may be an IC, a transistor, or a passive component. It can also contain internal circuitry. By using this chart, you can determine the impedance of a circuit board and use it to design an electrical circuit.

The Smith chart can be used to identify the different types of impedance models encountered in pcb design. It has three shapes: bounded, unbounded, and inverted. A point in the center of a Smith chart represents an unbounded impedance model, whereas a point on the outer circle represents an inverted impedance model.

By using a Smith chart to calculate impedance, you can easily match the source and destination impedances. You can then calculate the size of your matching network. The size of the matching network depends on the amount of shift required between the source and the destination impedance. In addition, the series and parallel L and C values shift a point along the constant resistance and reactance curves. If the resistance decreases, you can add more R values to the end of the line.

Using a 3D field solver

PCB impedance calculation is a necessary step during the PCB design process. It involves calculating the transmission line or trace impedance on the PCB based on the design configuration. If the PCB is complex or contains multiple layers, the use of a 3D field solver can yield the most accurate impedance calculation.

Impedance calculation models usually assume that the cross-section is rectangular and that the current is perfectly returned. However, real cross-sections may be polygonal and can even cross gaps in the reference layer. This can cause significant distortions on the signals, especially in high-speed nets.

The solver supports two types of ports: wave ports and lumped ports. In both cases, you must explicitly define which type of port you want to use. You can either specify a plane for the wave port by using the geometry or define it manually by using the Wave Custom Size type.

Most 3D field solvers generate S-parameter behavioral models. These models are a simplified schematic representation of the actual device. As such, they require many iterations. For instance, you can create a simulation with many circuit models and compare their results.

PCB impedance calculations are essential for PCB design. It is important to model the regulated impedance of your PCB, so that you can avoid impedance mismatches. In addition, it is important to work closely with your PCB manufacturer. Your PCB manufacturer may have a dedicated CAM department that can provide appropriate indications for solving impedance-related design questions. However, it is important not to completely hand over control of impedance issues to an external party.

How to Choose and Use Roger PCB Material in RF and Microwave Designs

/0 Kommentarer/i /af

How to Choose and Use Roger PCB Material in RF and Microwave Designs

When choosing a PCB material for your next RF or microwave design, there are a few important considerations you should make. These include the bearing temperature, the maximum and minimum operating temperatures, and the reversibility of the material. For example, if your project requires a high bearing temperature, you’ll probably want to use Rogers PCB.
RF

If your circuit board design requires a high-frequency and low-dielectric constant material, you might be wondering how to choose and use Roger PCB material. Fortunately, you have several options. Teflon-based cores are available from many companies. These materials can be very flexible. This makes them great for single-bend applications. They also offer the high reliability and electrical performance associated with a PTFE substrate.

Microwave

When deciding which PCB material is best for your RF or microwave design, consider the type of frequencies that you need to cover. In general, you should choose a low dielectric constant material for these applications. Low dielectric constant materials have low signal losses and are ideal for RF microwave circuits.

High-speed

The selection of the right PCB material is crucial for radio-frequency and microwave designs. Rogers PCB material has the characteristics necessary to withstand high temperatures and maintain reliability. It has a high glass transition temperature of approximately 280 degrees Celsius and stable expansion characteristics throughout the entire circuit processing temperature range.

Dielectric layer

When designing RF or microwave PCBs, the dielectric layer is an important performance parameter. The material must have a low dielectric constant and smallest tangent to resist dielectric losses, and it must have high thermal and mechanical stability. Teflon is an excellent material for this purpose. It is also known as Teflon PCBs. A dielectric material with a low thermal coefficient of expansion is necessary for the stability of a filter or oscillator. The material should also have matching X and Z-axis coefficients of thermal expansion.

Trace width

Using Rogers PCB material is an excellent way to improve the performance of your designs. This dielectric material has a wide range of dielectric constant values, which makes it an excellent choice for high-speed applications. Besides, it is compatible with FR-4.

Signal loss tolerance

As PCB designs become more complex, smaller, and faster, the need for control over impedance becomes increasingly important. Controlling substrate impedance is essential to allowing signals to travel efficiently across the trace or reference plane. Improper substrate impedance can cause signals to fall outside of their specified range. By incorporating a Rogers 4000 Series laminate, designers can provide impedance control while still enhancing the overall design. This is particularly important in high-speed digital applications.

PTFE

When implementing RF or microwave PCBs, the dielectric constant (Dk) of the circuit board material is critical. The higher the dielectric constant, the shorter the wavelength of the circuit. A PTFE Rogers PCB material with a high Dk is a great choice for microwave PCBs.

Rogers RT/Duroid 5880

RT/Duroid 5880 is a glass microfiber reinforced PCB material, with low dielectric constant and low loss. This material is a good choice for microwave or RF designs. It has low density and is compatible with high-temperature soldering.

How Are Double Sided SMD Boards Assembled? Full Process and Comparison

/0 Kommentarer/i /af

How Are Double Sided SMD Boards Assembled? Full Process and Comparison

This article will compare the cost and assembly process of double-sided vs single-sided SMD boards. It will also cover the benefits and disadvantages of both types of boards. In addition, it will help you understand the differences between soldering and Solder paste printing.

Single-sided vs double-sided smd boards

Single-sided and double-sided SMD boards are different in many ways. Double-sided boards have more space and are capable of carrying more components and connections. They are a great choice for complicated electronics. Double-sided PCBs are generally more expensive and complex to assemble. Nevertheless, they have a few benefits.

Single-sided PCBs have a simpler process of manufacture. They do not require the use of a soldering iron and do not require a lot of complicated tools. Single-sided PCBs are available in a wide variety of materials and are less expensive in most cases. These boards can also be more flexible, resulting in lower production costs.

Double-sided boards have more surface area and are often preferred in complex circuits. Single-sided boards can be made with both through-hole and surface-mount components. However, in double-sided boards, the components are mounted on either the top or bottom side.

Double-sided boards offer better flexibility for complex circuits, but single-sided boards are a good option when space is an issue. Single-sided boards can accommodate larger circuits than double-sided PCBs, but a single-sided board can be too large. If you need to make an intricate circuit with many connections, you may have to install wire jumpers between components.

The benefits of double-sided boards include greater complexity in circuit layout and cost effectiveness. Double-sided PCBs are also more expensive because they require more stencils and additional equipment. Furthermore, double-sided PCBs may have higher overhead costs. Depending on the board’s design, double-sided PCBs may require more complex circuit design and more holes.

Solder paste printing vs soldering

Solder paste printing is a process that applies solder paste to bare boards and areas where components are mounted. The process can be complex and requires a detailed process. To ensure accuracy, solder paste is measured in 3D, allowing for a smaller margin of error. After the solder paste is applied to the bare board, the next step is to place the surface mount components. Machines are ideal for this, as they offer a precise and error-free process.

Solder paste comes in different types and qualities, and can be purchased in industrial quantities from large PCB assembly plants. It can also be purchased in smaller quantities from stencil vendors and solder paste suppliers. Both types of solder paste require proper storage, and must be kept in air-tight containers. Because solder paste has a large surface area, oxidation can be a serious problem.

Due to the complexity of electronic products, PCBA boards are becoming smaller. In addition, many PCBAs contain more than one type of component. Most PCBAs are packed with a combination of SMD and thru-hole components.

Too many different components can affect the soldering process.

Solder paste printing requires a precise printing process. The squeegee used for solder paste printing should be made of stainless steel and be at 45-60 degrees. The angle of the squeegee determines the amount of solder paste that is applied to the surface. Besides that, the pressure of the squeegee also determines the shape of the paste deposit. The speed of the stencil strip also affects the volume of solder paste that is printed. Too high a speed could result in high edges around the deposits.

Cost of assembling a double-sided smd board

Assembling a double-sided SMD board is more expensive and complicated than standard single-sided boards. The exact cost will depend on the specific setup. The two major differences are the number of through-holes and conductor placement. By comparing the two options, you can get a better idea of what the costs will be.

The process of double-sided SMD board assembly begins with the first side of the board being processed. Then the second side is soldered. During the reflow soldering process, the weight of the components will need to be considered. If the components are heavy, they can be secured with adhesive before soldering.

The average cost of PCB assembly ranges from three to four dollars to hundreds of dollars. However, the price depends on the design complexity and overhead expenses. Also, if the PCB requires drilling, the cost of manufacturing and assembly will be higher than the average.

The overall cost of assembling a double-sided SMD board depends on the design complexity and the performance requirements of the product. PCB assembly is a highly complex process that involves skilled human labor as well as automated machinery. Because the process involves many layers, the total cost increases with the number of components.

Forskellige typer af PCB-lodningsprocesser

/0 Kommentarer/i /af

Forskellige typer af PCB-lodningsprocesser

When it comes to PCB soldering, you have a few options. There is reflow, surface mount technology, and wave soldering. Learn more about them. Each one has its benefits and drawbacks. Which one is best for your PCB?

Bølgelodning

Wave soldering processes are used to solder electronic components on printed circuit boards. The process passes the PCB through a pot of molten solder, generating standing waves of solder that are used to form joints that are electrically and mechanically reliable. This process is most commonly used for through-hole component assembly, but it can also be used for surface-mounting.

Initially, wave soldering was used to solder through-holes. This process allowed for the development of double-sided and multi-layer PCBs. It eventually led to hybrid PCB assemblies using both through-hole and SMD components. Some circuit “boards” today consist of flexible ribbons.

In the early days, the wave soldering process used fluxes with a high rosin concentration. Usually, these liquid fluxes were only used for wave-soldering assemblies without SMDs. This method required expensive post-soldering cleaning.

Surface mount technology

Surface mount technology is a popular way to manufacture PCBs. It allows for miniaturization of components, which can then be mounted closer together on a printed circuit board. This enables integrated circuits to be smaller and provide more functionality. However, it does require more capital investment.

Surface mount technology involves soldering components on the surface of the PCB. It has advantages over other PCB soldering processes, such as through-hole mounting and wave-soldering. Compared to through-hole mount, surface mount PCBs can achieve higher packaging density and reliability. They can also be more resistant to vibration and impact. They are commonly used in consumer electronics.

Surface mount technology was first introduced in the 1960s and has become very popular in electronics. Today, there are a wide range of components made using surface-mount technology. This includes a large variety of transistors and analogue and logic ICs.

Selektiv lodning

Selective soldering for PCBs is a cost-effective process that enables manufacturers to sell their products more quickly and easily. Its advantages include the ability to protect sensitive components from heat and to reduce the amount of soldering time. Additionally, this process can be used to repair or rework boards once they have been soldered.

There are two main methods used for selective soldering. These include drag soldering and dip soldering. Each of these processes has its own advantages and disadvantages. As a result, it’s important to understand each of them before deciding which one is best for you.

Selective soldering has many benefits and is the preferred method for many PCB assemblies. It eliminates the need to manually solder all of the components of a circuit board, resulting in faster assembly. Furthermore, it reduces thermal abuse of the board.

PCB-typer og funktioner

/0 Kommentarer/i /af

PCB-typer og funktioner

PCB i medicinalindustrien

Den medicinske sektor er stærkt afhængig af PCB'er til en række produkter, herunder blodtryksmålere, infusionspumper og pulsmålere. Disse apparater leverer nøjagtige mængder væske til patienterne gennem bittesmå elektroniske komponenter. Efterhånden som teknologien forbedres, vil medicinalindustrien fortsætte med at finde nye anvendelser for PCB.

Trykte kredsløbsplader

Printkort er en vigtig del af mange industrier. De bruges i en lang række produkter, fra store maskiner til forbrugerapparater. Her er nogle almindelige anvendelser for disse printkort. I industrielle applikationer skal de kunne modstå høj effekt og ekstreme temperaturer. De kan også blive udsat for skrappe kemikalier og vibrerende maskiner. Det er derfor, mange industrielle PCB'er er lavet af tykkere og termisk resistente metaller.

Anvendelsesmulighederne for printkort er mange, fra at forsyne et køleskab med strøm til at muliggøre Internet of Things. Selv enheder, der ikke tidligere var elektroniske, bruger nu elektroniske komponenter. Printplader er også meget udbredte i industrien, hvor de forsyner meget af udstyret i distributionscentre og produktionsanlæg med strøm.

Miljømæssig påvirkning

PCB er plastkemikalier, der bruges i fremstillingen af mange produkter. De blev først produceret i 1929 og blev brugt meget i fugemasser, blæk og skæreolier. I 1966 blev de opdaget i De Store Søer, hvilket førte til et forbud mod produktion og import af dem i hele Nordamerika. PCB-niveauerne begyndte at falde indtil slutningen af 1980'erne, hvor de begyndte at stige igen.

Ud over de kemiske forbindelser indeholder PCB også analoger, der forårsager hormonforstyrrelser og neurotoksicitet hos mennesker. Disse analoger er polybromerede biphenyler og deler mange af de samme miljøproblemer. De har lignende kemiske egenskaber og er modstandsdygtige over for hydrolyse, syre og temperaturændringer. Derudover kan de generere dibenzodioxiner, hvis de udsættes for høje temperaturer og kemikalier.

PCB'er med flere lag

Flerlags-printkort er en populær type printkort og bruges i en lang række applikationer. Flerlagsdesignet er ideelt til elektronik, der har brug for fleksibilitet, lav vægt og holdbarhed. Disse printkort kan fungere som både fleksible og stive printkort og bruges i næsten alle moderne komplekse elektroniske enheder.

PCB er også almindeligt anvendt i medicinalindustrien. De bruges i røntgen- og CAT-scanningsudstyr samt i blodtryks- og sukkertestapparater. Flerlags-PCB'er er særligt nyttige i disse applikationer, fordi de kan være ekstremt små, samtidig med at de har en kraftig ydeevne.

Sundhedsmæssige virkninger

Lave niveauer af PCB-eksponering vil sandsynligvis ikke have nogen negative helbredseffekter. Store eksponeringer kan dog resultere i højere risiko for negative helbredseffekter. Aboriginals, jægere og lystfiskere samt familier er særligt udsatte. Heldigvis er der flere måder at reducere sin PCB-eksponering på. Blandt andet ved at spise fødevarer, der er fri for PCB, vaske hænder ofte og undgå forurenet vand og fisk.

Undersøgelser har vist, at PCB kan forårsage negative helbredseffekter hos mennesker og dyr. Det er blevet klassificeret som et sandsynligt kræftfremkaldende stof og kan påvirke hjernens udvikling og neurologiske funktion. Eksponering for PCB kan også føre til dårlig korttidshukommelse og nedsat IQ.

Sådan håndterer du jordforbindelse i højfrekvensdesign

/0 Kommentarer/i /af

Sådan håndterer du jordforbindelse i højfrekvensdesign

Højfrekvensdesign skal tage højde for spørgsmålet om jordforbindelse. Der er flere problemer, der skal løses, når det drejer sig om jordforbindelse. Det drejer sig bl.a. om jordledernes og jordforbindelsernes impedans, DC-stien, der dominerer lavfrekvenssignalerne, og enkeltpunktsjording.

Jordledernes impedans

Jordingselektroden i et typisk jordet elektrisk system er parallel med de jordstænger, der er placeret på ledningssiden af stikledningen, transformere og master. Stangen, der testes, er forbundet til jordelektroden. Den ækvivalente modstand i jordstængerne på ledningssiden er ubetydelig.

En enkeltpunkts jordingsmetode er acceptabel til frekvenser under 1 MHz, men den er mindre ønskværdig til høje frekvenser. En enkeltpunkts jordledning vil øge jordimpedansen på grund af ledningsinduktans og sporkapacitans, mens omstrejfende kapacitans vil skabe utilsigtede jordreturstier. Til højfrekvente kredsløb er det nødvendigt med flerpunktsjording. Men denne metode skaber jordsløjfer, der er modtagelige for induktion af magnetfelter. Derfor er det vigtigt at undgå at bruge hybride jordsløjfer, især hvis kredsløbet indeholder følsomme komponenter.

Jordstøj kan være et stort problem i højfrekvente kredsløb, især når kredsløbene trækker store varierende strømme fra forsyningen. Denne strøm flyder i den fælles jordretur og forårsager fejlspænding, eller DV. Denne varierer med kredsløbets frekvens.

Impedans af forbindelsesledere

Ideelt set bør bondingledernes modstand være mindre end en milli-ohm. Men ved højere frekvenser er en bondingleders opførsel mere kompleks. Den kan udvise parasitiske effekter og restkapacitans parallelt. I dette tilfælde bliver bondinglederen til et parallelt resonanskredsløb. Den kan også udvise høj modstand på grund af skin-effekten, som er strømmen, der løber gennem lederens ydre overflade.

Et typisk eksempel på en ledningsbåret interferenskobling er en motor eller et koblingskredsløb, der føres ind i en mikroprocessor med en jordretur. I denne situation er jordlederens impedans højere end dens driftsfrekvens, og det vil sandsynligvis få kredsløbet til at resonere. Derfor er udligningsledere typisk udlignet på flere punkter med forskellige udligningslængder.

DC-vejen dominerer for lavfrekvente signaler

Det er en udbredt antagelse, at DC-stier, der dominerer for lavfrekvente signaler, er lettere at implementere end højfrekvente kredsløb. Denne metode har dog flere begrænsninger, især i integrerede implementeringer. Disse begrænsninger omfatter flimmerstøj, DC-strømforskydninger og store tidskonstanter. Desuden bruger disse designs normalt store modstande og kondensatorer, som kan producere stor termisk støj.

Generelt vil returstrømmen fra højfrekvente signaler følge den vej, der har mindst loopareal og mindst induktans. Det betyder, at størstedelen af signalstrømmen vender tilbage på planet via en smal sti direkte under signalsporet.

Jordforbindelse med ét punkt

Enkeltpunktsjording er et vigtigt element i beskyttelsen af kommunikationsanlæg mod lynnedslag. Ud over effektiv potentialudligning giver denne teknik også strukturel lynbeskyttelse. Den er blevet testet grundigt i områder, der er udsat for lynnedslag, og har vist sig at være en effektiv metode. Enkeltpunktsjording er dog ikke det eneste, der skal tages i betragtning.

Hvis forskellen i effektniveau mellem kredsløbene er stor, er det måske ikke praktisk at bruge seriejording med ét punkt. Den resulterende store returstrøm kan forstyrre kredsløb med lav effekt. Hvis effektniveauforskellen er lav, kan man bruge en parallel enkeltpunktsjording. Denne metode har dog mange ulemper. Ud over at være ineffektiv kræver enkeltpunktsjording en større mængde jordforbindelse, og det øger også jordimpedansen.

Jordingssystemer med ét punkt bruges generelt i design med lavere frekvenser. Men hvis kredsløbene arbejder ved høje frekvenser, kan et flerpunkts jordingssystem være et godt valg. Jordplanet i et højfrekvent kredsløb bør deles af to eller flere kredsløb. Det vil reducere risikoen for magnetiske sløjfer.

Interferens med strøm

Effektforstyrrelser kan forringe et kredsløbs ydeevne og kan endda forårsage alvorlige problemer med signalintegriteten. Derfor er det bydende nødvendigt at håndtere effektinterferens i højfrekvensdesign. Heldigvis findes der metoder til at håndtere disse problemer. De følgende tips vil hjælpe dig med at reducere mængden af effektinterferens i dine højfrekvensdesign.

Først skal du forstå, hvordan elektromagnetisk interferens opstår. Der er to hovedtyper af interferens: kontinuerlig og impuls. Kontinuerlig interferens opstår fra menneskeskabte og naturlige kilder. Begge typer interferens er kendetegnet ved en koblingsmekanisme og en respons. Impulsstøj opstår derimod med mellemrum og inden for kort tid.

Fejlanalyse af loddefejl på PCB-pads af tin til nedsænkning

/0 Kommentarer/i /af

Fejlanalyse af loddefejl på PCB-pads af tin til nedsænkning

Soldering defects are a common cause of PCB failure. There are several different types of defects that can lead to PCB failure. The article below explores three types of defects: Wetting, Plating through hole barrel cracking, and Liquid fluxes.

Wetting defects

Exposure to environmental factors during the manufacturing process can affect the wetting ability of immersion tin pcb pads. This can reduce assembly yield and second level reliability. Therefore, it is important to avoid or correct poor wetting defects. This research explored the effects of different temperature conditions on the wetting ability of these pads.

Immersion tin pads exhibit a variety of defects that can cause the assembly process to fail. Unlike dewetting, which is a defect in which the soldering joint is not formed, wetting defects occur when the molten solder does not adhere to the wettable surface of the PCB pads or components. This can result in holes or voids in the solder joints.

Non-wetting defects can also cause serious structural issues. In addition, they may result in poor electrical conductivity, loose components, and poor PCB pad performance.

Plating through hole barrel cracking

This study evaluated the reliability of immersion tin pcb pads through a failure analysis of soldering defects. To do this, we studied the behavior of the intermetallics inside solder joints by SEM. We compared the results of the aged and non-aged assemblies to understand how the intermetallics affect joint reliability.

The results of the investigation show that the electroless nickel coating on immersion tin PCB pads is characterized by deep crevasses and fissures. These open boundaries are attributed to the corrosive environment generated during ENIG plating. This problem can be solved by introducing a nickel controller into the plating process. This countermeasure helps to maintain good wettability in the pad and prevent oxidation.

Liquid fluxes

This failure analysis of soldering defects also includes the analysis of the flux used in the process. The use of different liquid fluxes in the reflow process may lead to different results. One method used for analyzing the effects of flux on soldering defects on immersion tin PCB pads is to assemble the flip-chip assemblies with readout chips on the bottom.