Dip-lödning och SMD-lödda enheter

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Dip-lödning och SMD-lödda enheter

Dip-lödning och smd-lödda enheter är två olika bearbetningsmetoder som används för att montera elektroniska enheter. Båda metoderna använder en återflödesprocess som innebär en gradvis uppvärmning av lödpastan. När återflödesprocessen är framgångsrik binder den smälta lödpastan effektivt de monterade komponenterna till PCB, vilket skapar en stabil elektrisk anslutning. De två metoderna har flera gemensamma egenskaper.

Asymmetrisk våglödning

Asymmetrisk våglödning innebär att man bildar en ring av lödtenn som omger detaljen och kan separera den från den omgivande luften. Det skapar också en barriär mellan lodet och syre. Den här lödmetoden är enkel och mångsidig, men den kan innebära stora utmaningar, särskilt när man använder ytmonterade enheter.

Våglödningsprocessen är en av de mest använda lödningsmetoderna. Det är en bulklödningsprocess som gör det möjligt för tillverkare att snabbt massproducera många kretskort. Kretskorten passerar över det smälta lodet, som skapas av en pump i en panna. Vågen av lödtenn fäster sedan på komponenterna på kretskortet. Under processen måste kretskortet kylas och blåsas för att förhindra att lodet förorenar kretskortet.

Fluxbarriär

Flussmedel är en vätska som gör att smält lod flyter och avlägsnar oxider från ytan. Det finns tre typer av flussmedel. Dessa inkluderar vattenbaserad, alkoholbaserad och lösningsmedelsbaserad. Under lödningsprocessen måste kortet förvärmas för att flussmedlet ska aktiveras. När lödningen är klar måste flussmedlet avlägsnas med hjälp av lösningsmedelsbaserade eller vattenbaserade borttagningsmedel.

Ett flussmedel av hög kvalitet är avgörande för att uppnå önskat resultat under lödningsprocessen. Ett flussmedel av hög kvalitet förbättrar lodets vätnings- och bindningsegenskaper. Ett flussmedel med hög aktiveringsgrad kan dock öka risken för oxidering, vilket inte alltid är önskvärt.

Kalla leder

Vid kall lödning smälter eller återflödar inte legeringen helt. Detta kan få allvarliga konsekvenser i en elektronisk enhet. Detta kan påverka lödets ledningsförmåga och resultera i en misslyckad krets. För att testa kalla lödfogar, anslut en multimeter till terminalerna. Om multimetern indikerar ett motstånd på över 1000 ohm har den kalla fogen misslyckats.

Lödning av ett mönsterkort kräver bra lödfogar, vilket säkerställer produktens funktion. Generellt sett är en bra lödfog slät, ljus och innehåller en kontur av den lödda tråden. En dålig lödfog leder till kortslutning på kretskortet och orsakar skador på enheten.

Tillsats av metall till kretskort

Att lägga till metall på mönsterkort med dip- eller smd-lödning innebär att man lägger till en fyllnadsmetall på mönsterkortet före lödning. Mjuklödning är den vanligaste metoden för att fästa små komponenter på kretskortet. Till skillnad från traditionell lödning smälter inte mjuklödningen komponenten, eftersom lödningen inte kan fästa på den oxiderade ytan. Istället tillsätts en fyllnadsmetall, vanligtvis en tenn-blylegering.

Innan du lödar komponenten är det viktigt att du förbereder lödkolven till 400degC. Denna värme måste vara tillräckligt hög för att smälta lodet på spetsen. Det är bra att förtenna spetsen före lödningen för att underlätta värmeöverföringen. Dessutom hjälper det att hålla komponenterna organiserade så att lödningen inte blir stressig.

Manuell vs automatiserad våglödning

Utrustning för våglödning finns i olika former, inklusive robotar, manuella och selektiva system för nedsänkning. Det finns flera fördelar och nackdelar med varje typ. Du bör köpa den som bäst passar din verksamhets behov. En slimmad verksamhet bör t.ex. överväga att köpa den enklaste modellen. Du bör dock också överväga kostnaden för utrustningen. I de flesta fall kostar en manuell våglödningsutrustning mindre än en automatiserad maskin.

Manuell lödning är långsammare än automatiserad våglödning och är känslig för mänskliga fel. Selektiv lödning eliminerar dock dessa problem genom att operatören kan programmera exakta punkter för varje komponent. Selektiv lödning kräver inte heller något lim. Dessutom krävs inga dyra våglödningspallar och den är kostnadseffektiv.

Problem med SMD-lödning

Lödproblem kan uppstå av flera olika anledningar. En vanlig orsak är fel pastamall vid användning av lodflussmedel eller fel inställning av monteringsmataren. Andra problem är otillräcklig mängd lödtenn och dålig lödbarhet hos komponenterna eller elektroderna. Dessa fel kan leda till att svetspunkten får oväntade former. Lödkulor, istappar och hål kan också bli resultatet av felaktig lödning.

En annan vanlig orsak till icke vätande lödfogar är felaktig rengöring. Otillräcklig vätning innebär att lodet inte fäster ordentligt på komponenten. Följden blir att komponenterna inte är anslutna och kan falla av.

Lödningsmetoder för PCB-chip-paket och processer

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Lödningsmetoder för PCB-chip-paket och processer

Soldering is a critical part of a PCB chip package. Soldering processes involve a combination of techniques, including focused IR, convection, and non-focused IR. Each method involves a gradual heating of the package, followed by cooling the entire assembly.

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.

Inspektion

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

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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.

Hur man gör en modell för impedansberäkning av kretskort

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Hur man gör en modell för impedansberäkning av kretskort

Using a Smith chart

Smith-diagrammet är ett användbart verktyg när du vill bestämma impedansen i en krets. Det är en visuell representation av den komplexa resistansen kontra frekvensen i en elektrisk krets. Det visar också impedansens läge i förhållande till frekvensen, vilket är nödvändigt för stabilitetsanalys och för att undvika svängningar. Många datorer har möjlighet att visa impedansvärden numeriskt, men Smith-diagrammet hjälper dig att visualisera möjligheterna.

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

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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.

Hur monteras dubbelsidiga SMD-kort? Fullständig process och jämförelse

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Hur monteras dubbelsidiga SMD-kort? Fullständig process och jämförelse

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.

Olika typer av PCB-lödprocesser

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Olika typer av PCB-lödprocesser

När det gäller PCB-lödning har du några alternativ. Det finns återflödeslödning, ytmonteringsteknik och våglödning. Läs mer om dem. Var och en har sina fördelar och nackdelar. Vilken är bäst för ditt mönsterkort?

Våglödning

Våglödningsprocesser används för att löda elektroniska komponenter på kretskort. I processen passerar kretskortet genom en behållare med smält lod, vilket genererar stående vågor av lod som används för att bilda fogar som är elektriskt och mekaniskt tillförlitliga. Denna process används oftast för montering av komponenter genom hål, men den kan också användas för ytmontering.

I början användes våglödning för att löda genomgående hål. Denna process gjorde det möjligt att utveckla dubbelsidiga och flerskiktade mönsterkort. Det ledde så småningom till hybridkretskort med både genomgående hål och SMD-komponenter. Vissa "kretskort" består idag av flexibla band.

I början av våglödningsprocessen användes flussmedel med hög kolofoniumkoncentration. Vanligtvis användes dessa flytande flussmedel endast för våglödning av monteringar utan SMD. Denna metod krävde dyr rengöring efter lödningen.

Teknik för ytmontering

Ytmonteringsteknik är ett populärt sätt att tillverka kretskort. Den möjliggör miniatyrisering av komponenter, som sedan kan monteras närmare varandra på ett kretskort. Detta gör att integrerade kretsar kan vara mindre och ge mer funktionalitet. Det kräver dock större kapitalinvesteringar.

Ytmonteringsteknik innebär att komponenterna lödas på kretskortets yta. Den har fördelar jämfört med andra PCB-lödningsprocesser, t.ex. genomgående hålmontering och våglödning. Jämfört med genomgående hålmontering kan ytmonterade PCB uppnå högre förpackningsdensitet och tillförlitlighet. De kan också vara mer motståndskraftiga mot vibrationer och stötar. De används ofta i konsumentelektronik.

Ytmonteringstekniken introducerades på 1960-talet och har blivit mycket populär inom elektronik. Idag finns det ett brett utbud av komponenter som tillverkas med ytmonteringsteknik. Detta inkluderar en stor mängd olika transistorer och analoga och logiska IC.

Selektiv lödning

Selektiv lödning av mönsterkort är en kostnadseffektiv process som gör det möjligt för tillverkare att sälja sina produkter snabbare och enklare. Bland fördelarna finns förmågan att skydda känsliga komponenter från värme och att minska lödtiden. Dessutom kan processen användas för att reparera eller omarbeta kretskort efter lödning.

Det finns två huvudsakliga metoder som används för selektiv lödning. Dessa inkluderar draglödning och dopplödning. Var och en av dessa processer har sina egna fördelar och nackdelar. Därför är det viktigt att du förstår var och en av dem innan du bestämmer dig för vilken som är bäst för dig.

Selektiv lödning har många fördelar och är den metod som föredras vid många kretskortsmonteringar. Det eliminerar behovet av att manuellt löda alla komponenter på ett kretskort, vilket resulterar i snabbare montering. Dessutom minskar det termiska missbruket av kortet.

PCB-typer och funktioner

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PCB-typer och funktioner

PCB inom medicinsk industri

Den medicinska sektorn är starkt beroende av PCB för en mängd olika produkter, inklusive blodtrycksmätare, infusionspumpar och hjärtfrekvensmonitorer. Dessa enheter levererar exakta mängder vätska till patienter genom små elektroniska komponenter. I takt med att tekniken förbättras kommer den medicinska industrin att fortsätta att hitta nya användningsområden för PCB.

Tryckta kretskort

Tryckta kretskort är en viktig del av många industrier. De används i en mängd olika produkter, från stora maskiner till konsumentapparater. Här är några vanliga användningsområden för dessa kretskort. I industriella tillämpningar måste de tåla hög effekt och extrema temperaturer. De kan också utsättas för starka kemikalier och vibrerande maskiner. Det är därför många industriella mönsterkort tillverkas av tjockare och värmebeständiga metaller.

Användningsområdena för kretskort är många, från att driva ett kylskåp till att möjliggöra Internet of Things. Även enheter som tidigare inte var elektroniska använder nu elektroniska komponenter. Tryckta kretskort används också i stor utsträckning i industriella miljöer, där de driver mycket av utrustningen i distributionscentraler och tillverkningsanläggningar.

Miljöpåverkan

PCB är plastkemikalier som används i tillverkningen av många produkter. De tillverkades första gången 1929 och användes i stor utsträckning i tätningsmedel, bläck och skäroljor. År 1966 upptäcktes de i de stora sjöarna, vilket ledde till ett förbud mot tillverkning och import av dem i hela Nordamerika. PCB-nivåerna började sjunka fram till slutet av 1980-talet, då de började stiga igen.

Förutom de kemiska föreningarna innehåller PCB även analoger som orsakar endokrina störningar och neurotoxicitet hos människor. Dessa analoger är polybromerade bifenyler och har många av samma miljöproblem. De har liknande kemiska egenskaper och är beständiga mot hydrolys, syra och temperaturförändringar. Dessutom kan de bilda dibensodioxiner om de utsätts för höga temperaturer och kemikalier.

PCB med flera lager

Multilayer PCB är en populär typ av kretskort och används i en mängd olika applikationer. Flerskiktskonstruktionen är idealisk för elektronik som kräver flexibilitet, låg vikt och hållbarhet. Dessa kort kan fungera som både flexibla och styva kretskort och används i nästan alla moderna komplexa elektroniska enheter.

PCB används också ofta inom den medicinska industrin. De används i röntgen- och datortomografiutrustning samt i apparater för blodtrycks- och sockertestning. Flerskikts-PCB är särskilt användbara i dessa tillämpningar eftersom de kan vara extremt små samtidigt som de ger kraftfull prestanda.

Hälsoeffekter

Låga nivåer av PCB-exponering har sannolikt inga negativa hälsoeffekter. Stora exponeringar kan dock leda till högre risk för negativa hälsoeffekter. Ursprungsbefolkningar, jägare och sportfiskare samt familjer är särskilt utsatta. Lyckligtvis finns det flera sätt att minska sin PCB-exponering. Bland annat genom att äta livsmedel som är fria från PCB, tvätta händerna ofta och undvika förorenat vatten och fisk.

Studier har visat att PCB kan orsaka negativa hälsoeffekter hos människor och djur. De har klassificerats som sannolikt cancerframkallande och kan påverka hjärnans utveckling och neurologiska funktion. Exponering för PCB kan också leda till försämrat korttidsminne och sänkt IQ.

Hur man hanterar jordning i högfrekvensdesign

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Hur man hanterar jordning i högfrekvensdesign

High frequency designs need to address the issue of grounding. There are several issues that need to be addressed when it comes to grounding. These include the impedance of grounding conductors and grounding bonds, DC path dominating low-frequency signals, and single-point grounding.

Impedance of grounding conductors

The grounding electrode of a typical grounded electrical system is in parallel with the ground rods located on the line side of the service, transformers, and poles. The rod under test is connected to the grounding electrode. The equivalent resistance of the line side ground rods is negligible.

A single-point grounding method is acceptable for frequencies below one MHz, but it is less desirable for high frequencies. A single-point grounding lead will raise the ground impedance due to wire inductance and track capacitance, while stray capacitance will create unintended ground return paths. For high-frequency circuits, multipoint grounding is necessary. However, this method creates ground loops that are susceptible to magnetic field induction. Therefore, it is important to avoid using hybrid ground loops, especially if the circuit will contain sensitive components.

Ground noise can be a major problem in high frequency circuits, especially when the circuits draw large varying currents from the supply. This current flows in the common-ground return and causes error voltage, or DV. This varies with the frequency of the circuit.

Impedance of bonding conductors

Ideally, the resistance of bonding conductors should be less than one milli-ohm. However, at higher frequencies, the behavior of a bonding conductor is more complex. It can exhibit parasitic effects and residual capacitance in parallel. In this case, the bonding conductor becomes a parallel resonant circuit. It can also exhibit high resistance due to the skin effect, which is the flow of current through the outer surface of the conductor.

A typical example of a conducted interference coupling is a motor or switching circuit fed into a microprocessor with an earth return. In this situation, the earthing conductor’s impedance is higher than its operating frequency, and it is likely to cause the circuit to resonant. Because of this, bonding conductors are typically bonded at multiple points, with different bonding lengths.

DC path dominating for low-frequency signals

It is widely assumed that DC path dominating for low-frequency signals is easier to implement than high-frequency circuits. However, this method has several limitations, especially in integrated implementations. These limitations include flicker noise, DC current offsets, and large time constants. Moreover, these designs usually use large resistors and capacitors, which can produce large thermal noise.

In general, the return current of high-frequency signals will follow the path of least loop area and least inductance. This means that the majority of the signal current returns on the plane via a narrow path directly below the signal trace.

Single-point grounding

Single-point grounding is an essential element in protecting communications sites from lightning. In addition to effective bonding, this technique offers structural lightning protection. It has been extensively tested in lightning-prone areas and has proven to be an effective method. However, single-point grounding isn’t the only consideration.

If the power level difference between the circuits is large, it may not be practical to use series single-point grounding. The resulting large return current can interfere with low-power circuits. If the power level difference is low, a parallel single-point grounding scheme can be used. However, this method has many disadvantages. In addition to being inefficient, single-point grounding requires a larger amount of grounding, and it also increases the ground impedance.

Single-point grounding systems are generally used in lower frequency designs. However, if the circuits are operated at high frequencies, a multipoint grounding system can be a good choice. The ground plane of a high-frequency circuit should be shared by two or more circuits. This will reduce the chances of magnetic loops.

Power interference

Power interferences can degrade the performance of a circuit and can even cause serious signal integrity problems. Hence, it is imperative to deal with power interferences in high frequency design. Fortunately, there are methods for dealing with these problems. The following tips will help you reduce the amount of power interference in your high frequency designs.

First, understand how electromagnetic interferences occur. There are two main types of interference: continuous and impulse. Continuous interference arises from man-made and natural sources. Both types of interference are characterized by a coupling mechanism and a response. Impulse noise, on the other hand, occurs intermittently and within a short time.

Felanalys av lödningsdefekter på PCB-pads med nedsänkt tenn

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Felanalys av lödningsdefekter på PCB-pads med nedsänkt tenn

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.