SMD Vs THT Vs SMT

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SMD Vs THT Vs SMT

When deciding which type of PCB to use, it’s important to understand the differences between SMD and THT. Each type has advantages and disadvantages. SMT requires advanced equipment and a custom stencil, while THT uses hand soldering to attach components. Because of these differences, SMT is generally the better choice for large-scale production and for high-speed applications. In contrast, THT is more appropriate for smaller projects and prototypes.

smd vs tht vs smt

In electronics, surface mount technology refers to the process of mounting electronic components directly onto a PCB. Its advantages include the ability to produce smaller PCBs. It replaces the traditional through-hole technology.

Typically, SM components are smaller than their through-hole counterparts and have contact terminals on the end of the component’s body. Many components are available in SMD packages, including capacitors, inductors, and resistors.

Surface mount devices are generally less expensive than their through-hole counterparts, but they require more sophisticated production technology and design. The increased capital investment is offset by higher throughput with a fully automated setup. The faster production time helps make them the better choice for many manufacturers.

The main differences between SMT and TH components are mechanical stability and fine-pitch requirements. In addition to being cheaper, SMT components are easier to assemble in large quantities, especially for smaller parts. Using Pick and Place machines and a Reflow Oven, SMT components are assembled at high speeds. However, SMT components require more training and expensive equipment to solder them properly.

THT requires more drilling than SMT, but it provides stronger mechanical bonds. It is suitable for high-reliability applications, where components are exposed to greater stress. However, the extra drilling is a drawback and increases the cost of the circuit board.

While SMT requires less drilling of the PCB, through-hole assembly can be much more expensive. However, it can be more efficient. In addition, SMT can produce smaller PCBs with fewer drill holes, which will save you money. In addition, SMT uses automated machines to place the components, which makes it cheaper than THT.

Surface mount technology is a budget-friendly alternative to through-hole technology, which requires highly skilled operators and expensive equipment. In addition to cost savings, surface mount components are more reliable than through-hole components. Surface mount technology also allows for higher component density per unit area.

However, SMT components are often smaller than through-hole components. Because of their size, they often require magnification to read their markings. This makes them less desirable for prototyping, rework, and repair, but it is possible to repair these components with a soldering iron. But this requires considerable skill and is not always feasible.

Surface mount devices come in many shapes and materials. They are classified into different categories. Some are passive, like capacitors and resistors. Others are active, such as diodes. A mixed device may combine both types of devices, such as an integrated circuit.

Surface mount technology is becoming the mainstay of the PCB industry, but it is important to keep in mind that through-hole technology may be better for certain applications. It is more reliable than surface mount technology, and it is used for many applications in the military. It is also easier to test, prototype, and replace components. A breadboard with through-hole components is ideal for prototyping.

6 Basic Rules of PCB Layout

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6 Basic Rules of PCB Layout

PCB layout involves designing a circuit with multiple layers. Some of the fundamental rules of PCB design are as follows: Avoid multiple ground planes. Make analog circuit signals direct and short. Avoid using three distinct capacitors on a single PCB. You can also read our articles on multi-layer PCB design and how to design a multi-layer PCB.

Designing a multi-layer PCB

When you are designing a multi-layer PCB, there are a few important things that you should consider. One of these is that the copper traces should maintain signal and power integrity. If they are not, then they could affect the quality of current. This is why it is necessary to use controlled impedance traces. These traces should be thicker than normal to prevent overheating.

Once you are clear on what you want, you can start designing the PCB. The first step in designing a multilayer PCB is to create a schematic. It will serve as the basis for your entire design. Start by opening a schematic editor window. You can then add and rotate details as needed. Make sure that the schematic is accurate.

Creating a single ground plane

Creating a single ground plane on a PCB layout helps reduce the amount of nonuniform voltages across a circuit board. This is accomplished by creating vias or through holes to connect the ground plane with other parts of the board. It also helps reduce noise produced by variations in return current.

While defining a ground plane on a PCB, it is crucial to ensure that the ground plane is not covered with conductive rings because this can lead to electromagnetic interference or even ground loops. Ideally, the ground plane should be located under electronic components. It may be necessary to rearrange the placement of some traces and components to fit the ground plane.

Keeping analog circuit signals direct and short

When implementing a PCB layout for analog circuits, it is important to keep the analog signal traces short and direct. In addition, analog components must be located near each other, which will simplify direct routing. Keeping noisy analog components close to the center of the board will also help reduce noise.

In addition to keeping analog circuit signals direct and short, designers should also avoid obstructing the return paths. Plane splits, vias, slots, and cutouts can cause noise as the analog signal seeks the shortest path back to its origin. As a result, the signal can wander near the ground plane, generating significant noise.

Avoiding three distinct capacitors

When designing a PCB layout, it is best to avoid placing three distinct capacitors on power pins. This arrangement may lead to more problems than it solves. One way to avoid three distinct capacitors is to use traces and coffer fill. Then, place them as close to the device’s pin as possible.

This is not always possible, however, since the distance between traces is not always what was calculated during the design phase. This is a common problem that can lead to problems during the assembly process. When considering placement, remember that the placement of each component is crucial to its functionality.

Using power layer copper

Using power layer copper in PCB layout requires proper planning. In this part of the board, you must allocate a specific area of the board for power network. You can also use inner layer division to allocate this area. To add this layer, you should use the command “PLACE-SPLIT PLANE” and then select the network to be allocated for split. Once you have the power layer area allocated, you can then use the copper paving technique to place the copper in the split area.

In addition to achieving even copper coverage, you must make sure that the thickness of the board is compatible with its core. Using the power plane symmetry alone will not guarantee a perfect copper coverage, as the copper in this part will tear when contour routing. Copper up to the board edge also will not be compatible with scoring (V-cut) techniques. To avoid this issue, it is recommended that you indicate the copper zone on the mechanical layer and that it has a minimum width of 0.5mm.

Using a list of guidelines to place components on a PCB

Using a list of guidelines to place a component on a PCB can help minimize the overall cost of developing a new product while shortening the product development cycle. These guidelines also help ensure a smooth transition from prototype to production. These guidelines are applicable to both analog and digital circuits.

Most board designers follow a set of guidelines when designing a PCB. For example, a typical board design rule is to minimize the length of digital clock traces. However, many designers do not fully understand the rationale behind these guidelines. Among other things, high-speed traces must not cross gaps in the signal return plane.

How to Minimize the RF Effect in PCB Interconnect Design

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How to Minimize the RF Effect in PCB Interconnect Design

There are a number of different ways to minimize the RF effect in a PCB interconnect design. Some of these include ensuring that the traces are not in close proximity to one another, using a ground grid, and separating RF transmission lines from other traces.

Multilayer configuration

RF effect in PCB interconnect design is a common problem. This effect occurs mainly because of nonideal circuit properties. For example, if an IC is placed on two different circuit boards, its operating range, harmonic emissions, and interference susceptibility will be drastically different.

To minimize this effect, a multilayer configuration is necessary. Such a board should have a reasonable layout, high-frequency impedance, and simple low-frequency wiring. Using the correct substrate material minimizes signal loss, and it helps maintain consistent impedance throughout the circuits. This is crucial because signals transition from the circuit to the transmission lines, and they must have constant impedance.

Impedance is another issue with PCB interconnect design. It is the relative impedance of two transmission lines, beginning at the PCB surface and extending to the connector or coaxial cable. The higher the frequency, the more difficult it is to manage the impedance. Therefore, the use of higher frequencies seems to be a significant design challenge.

Creating a ground grid

One way to reduce the rf effect is to create a ground grid on your PCB. A ground grid is a series of box sections that is connected by traces to ground. Its purpose is to minimize the signal return path, while still maintaining low impedance. The ground grid can be either a single trace or a network of overlapping traces.

The ground plane acts as a reference to calculate the impedance of signal traces. In an ideal system, the return current stays on the same plane as the signal traces. However, in real systems, the return current may deviate from the ideal path due to various factors, including variations in the copper plating of the PCB and the laminate material used.

Separating RF transmission lines from other traces

When designing circuits with multiple traces, it is important to separate RF transmission lines from the rest of the circuit. Separation of these traces is important in order to prevent crosstalk. To achieve this, it is best to space RF transmission lines at least two trace widths apart. This distance reduces the amount of radiated emissions and minimizes the risk of capacitive coupling.

RF transmission lines are typically separated from other traces by striplines. In multi-layer printed circuit boards, striplines are most easily constructed on the inner layers. Like microstrip, striplines have ground planes above and below the RF transmission line. While striplines offer better isolation than microstrip, they tend to have a higher RF loss. For this reason, striplines are typically used for high-level RF signals.

Using PTFE ceramics

RF effect is a very real concern in PCB interconnect design. Due to high frequencies, the signals traveling on a trace can shift. This causes the dielectric constant to change depending on the speed of the signal and the tracing geometry. The dielectric constant of the PCB substrate material also affects the speed of the signal.

When comparing ceramics to solder, PTFE ceramics have an edge over FEP ceramics. While the former is cheaper and easier to fabricate, it will reduce signal reliability. Besides, PTFE ceramics are less likely to absorb moisture. However, if the PTFE ceramics are covered by hydrocarbons, the moisture absorption will increase.

Using symmetric stripline routing

Stripline routing is a common approach in digital circuit design. It uses a dielectric layer sandwiched between two ground planes with signal-carrying conductors in the center. This method is called symmetric stripline. Typical stripline dimensions are s=2.0, w=3.0, t=1.0, and b=5.0.

This method has two major advantages over microstrip. It allows for smaller traces, which provide more protection against aggressor signals. In addition, stripline routing can help minimize RF impact on the interconnect design. However, it requires careful consideration of the board layer stackup and the dielectric materials between ground planes.

As for the PCB track width, it should not exceed two inches. This is important for high-speed logic, which has a rise/fall time of five nanoseconds. It is advisable to terminate high-speed logic PCB tracks with a characteristic impedance, and to avoid voids in the reference plane.

EMI Degradation After Filling An Irrigation Pump

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EMI Degradation After Filling An Irrigation Pump

There are two different ways to analyze EMI degradation after filling an irrigation pump: radiation and conduction. The EMI degradation after filling depends on the type of glue material and how the input grounding process is performed. The EMI degradation is worsened by ethanol and water.

EMI degradation after filling

EMI degradation after filling power supplies is often referred to as the ‘filling effect’, which describes the loss of EMI sensitivity after a power supply has been filled. The degradation is a combination of radiation and conduction. The ‘filling effect’ occurs because the materials that make up the power supply undergo a series of changes. Some of these changes may be undesirable, while others can be beneficial.

Unwanted electromagnetic energy (EMI) is radiation that propagates into space through inductive and capacitive coupling. This unwanted energy is harmful to electronic devices and affects their functionality. This radiation is non-conducting, meaning that the signal is not conducted through the metal or other material. When the signal travels a long distance, its propagation is in the form of a wave. The wave is dominated by the radiation field at a far distance, while the induction field dominates at near-surface distances. Non-ionizing radiation, on the other hand, does not ionize the gases and does not affect electronic devices. Examples of non-ionizing radiation include RF, microwave ovens, infrared, and visible light.

Static electricity is another EMI source. Although it is difficult to identify the source of this noise, it can originate from natural sources such as lightning. In addition to affecting the performance of electronic devices, EMI can also cause safety problems in many systems. The most common cause of EMI is electrostatic discharge. Non-technical people recognize this type of noise as radio static, distorted television reception, and clicks in audio systems.

EMI degradation after filling with water

EMI degradation after filling with water after power supply switching can be classified into two types: radiation and conduction. The EMI degradation after filling with water is usually induced by changes in the temperature of the input ground and the conductive material used to make the water-filled capacitor. The conductive material includes aluminum and copper fibers, which have the highest intrinsic electrical conductivity. However, the surface of these fibers is prone to oxidation, which can affect the conductivity of the components. Moreover, some unscrupulous merchants might not provide consistent products.

EMI can affect the safety and performance of electrical appliances. These unwanted signals can interfere with radio communications and cause malfunction in nearby equipment. Hence, EMI shielding is an essential requirement for electronic devices. Various methods and materials are used for EMI shielding. Listed below are some of them:

Continuous carbon fiber composites exhibit better EMI SE and are better conductive than their discontinuous counterparts. A continuous carbon fiber composite with a carbon matrix exhibits a EMI SE of 124 dB. On the other hand, discontinuous carbon fibers significantly reduce the SE of the composites.

Switching power supplies have improved over linear regulators in terms of efficiency, but they still introduce discontinuous currents which can negatively affect the reliability of the system. EMI analysis is easier to perform for conductive noise than for radiated noise. The conductive noise can be evaluated using standard circuit analysis techniques.

EMI degradation after filling with ethanol

Electromagnetic interference (EMI) can affect electronic components and devices in many ways. For example, if a capacitor is subjected to a voltage peak that is higher than its nominal voltage, it can suffer diolectric degradation. This degeneration can result in malfunction or burn, depending on the component’s characteristic.

Electromagnetic interference is a common problem in modern technology. It causes malfunctions of electronic devices and may lead to damage to communication systems. This interference is caused by a variety of sources, including sparks from motor brushes, power circuit switches, inductive and resistive loads, relays, and circuit breaks. Even the slightest amount of EMI can degrade the performance of an electronic device and impair its safety. The most common source of EMI is electrostatic discharge (ESD), which many people recognize as static on radio stations, distorted television reception, and clicks in audio systems.

EMI can also be generated by switching power supplies. These power supplies are strong sources of EMI and require careful control. It is crucial to quantify the output noise of these power supplies to reduce the risk of EMI. This is a time-consuming and expensive process.

Sådan arrangerer du elegant PCB-silketryk på elegant vis

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Sådan arrangerer du elegant PCB-silketryk på elegant vis

There are a few things to consider when using PCB silkscreen. First, you have to decide how to arrange your silkscreen characters. This is very important because you will want to make sure they are not placed beneath a component or over a via pad. It is also important to make sure that the characters are not too big.

Using copper pads

PCB layout is a challenging process that requires careful planning. To achieve the desired result, it’s important to use the right tools and techniques. One way to do this is to use PROTEL AUTOTRAX under DOS, which enables you to edit strings and layouts. However, it is important to be aware that you may need to manually adjust pad sizes for two-legged chip components and four-row patch ICs.

Before you start creating a silkscreen, be sure to check with your CM for the recommended layout. Often, the CM will tell you to keep the silkscreen to only one side of the PCB.

Using reference designators

When designing a printed circuit board, using reference designators is a useful way to clearly identify components on the board. They usually start with a letter followed by a numeric value. Each reference designator will represent a particular class of component. Reference designators should be placed above the component so that they are clearly visible once it has been mounted on the PCB. Reference designators are usually painted with yellow or white epoxy ink or silkscreen.

The placement of reference designators is crucial. When placing a component on a PCB, ensure that it is placed as close as possible to its associated component. Similarly, if a component is placed vertically, it should have its reference designator on the bottom-left edge of the board. The placement of reference designators can reduce assembly errors. However, placing them beneath component symbols can make them difficult to read once mounted. Moreover, it is advisable not to place them on high-speed signal traces.

Using automatic alignment

PCBAs contain a variety of silkscreen markings and information. These include regulatory markings such as RoHS, FCC, and CE, as well as E-waste disposal markings. Additionally, there are PCBs with UL markings, which means the board has been fabricated by a UL-certified manufacturer.

These layers are then fused together using a process known as layer-up and bonding. The outer layer material consists of fiber glass or other material that has been pre-impregnated with epoxy resin, or prepreg. It also covers the original substrate and copper trace etchings. The layers are then assembled on a heavy steel table. The pins fit tightly into each other to prevent the layers from shifting.

The positioning of reference designators is very important. The designators should be close to the part they are meant to identify, and rotated appropriately to make them readable. It is also important that the part or component you are placing is not obscured by the silkscreen. This can make it difficult to read.

Manually specifying line widths

There are several reasons to manually specify line widths when arranging PCB silkscreened components. The first reason is that the line widths will have an impact on how your PCB silkscreen looks. If the line widths are too large or small, you may have trouble reading them. Additionally, too few lines may result in skips or blurry text. For this reason, it’s important to set a minimum line width of 0.15 mm (six mils). It is generally better to specify line widths of 0.18 mm to 20 mm.

There are other considerations as well, such as the size of the silkscreen fonts. If you are creating a silkscreen for a PCB, you should choose a font size of at least 0.05 inches for optimum readability. When placing reference designators, you should leave about 5 mils of space between each line. You should also ensure that they are oriented from left to right and bottom to top to avoid uneven silkscreening.

Using drafting features

PCB silkscreen is an important part of the finished circuit board and should be carefully crafted. To make sure your silkscreen looks its best, use the appropriate font sizes and line widths. Otherwise, you may end up with ink splots and a poor silkscreen layout.

One of the most common silkscreen errors is failing to mark polarized components clearly. For example, when drawing a PCB with electrolytic capacitors, always ensure that you mark the positive pin. For diodes, you should always use an “A” or “C” symbol to distinguish the anode from the cathode.

Sådan bruger du et par modstande til at forbedre nøjagtigheden af et multimeter

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Sådan bruger du et par modstande til at forbedre nøjagtigheden af et multimeter

For at forbedre nøjagtigheden af dit multimeter kan du bruge et par modstande og komponenter. De skal holdes på plads, så de forbliver i kontakt med multimeterets sonder. Du må ikke røre modstandene eller komponenterne med hænderne, da dette vil resultere i unøjagtige aflæsninger. For at undgå dette problem kan du fastgøre komponenterne på et breadboard eller bruge alligatorklemmer til at holde dem på plads.

Brug af shuntmodstande

Modstandsværdien af en shuntmodstand udtrykkes i mikroOhms. Modstanden for en shuntmodstand er normalt meget lille. Ved at bruge denne type modstand forbedres multimeterets nøjagtighed, fordi den ikke introducerer uønskede virkninger fra ledningsmodstanden. Det er dog vigtigt at bruge den med en Kelvin-forbindelse, fordi shuntmodstandens modstand har tendens til at glide med den omgivende temperatur.

Multimetre er følsomme over for belastningsspænding, så operatørerne skal være opmærksomme på belastningsspænding og opløsning. Uregelmæssig testning kan resultere i uventede produktfejl. Shuntmodstande forbedrer multimeterets nøjagtighed ved at give ekstra opløsning. Dette er især nyttigt for bænkmultimeter, som er i stand til at foretage målinger i fuld skala.

Indstilling af det korrekte område på et analogt multimeter

For at indstille det korrekte område på et analogt multimeter skal du starte med at indstille ohm-enheden til den laveste værdi. Generelt skal modstandsaflæsningen ligge mellem 860 og 880 ohm. Alternativt kan du bruge det lavere modstandsområde på 200 ohm til indlæring og øvelse.

Et multimeter med manuel måling har en drejeknap med mange valgmuligheder. Disse er normalt markeret med metriske præfikser. Multimetre med automatisk rækkevidde er derimod automatisk indstillet til det relevante område. Desuden har de en særlig "Logik"-testfunktion til måling af digitale kredsløb. Til denne funktion tilslutter man den røde ledning (+) til anoden og den sorte ledning (-) til katoden.

Det kan virke skræmmende at indstille området på et analogt multimeter, især hvis du aldrig har brugt et før. Denne opgave er imidlertid overraskende enkel og kan udføres med et par modstande. Så længe du er opmærksom på de forskellige intervaller, vil du få mere succes med denne opgave.

Brug af præcisionsstrømaftastningsmodstande

Nøjagtigheden af et multimeter kan forbedres ved at bruge præcisionsstrømsaftastningsmodstande. Disse komponenter kan købes i forskellige udgaver. De er nyttige til anvendelser, hvor det er nødvendigt at have den korrekte mængde strøm, der kommer ind og ud af et batteri. De er også nyttige til anvendelser, hvor temperaturfølsomhed er et problem.

Det optimale fodaftryk er C, med en forventet målefejl på 1%. De anbefalede dimensioner for fodaftryk er vist i figur 6. Følerens sporføring spiller også en vigtig rolle for målepræcisionen. Den højeste nøjagtighed opnås, når følespændingen måles ved modstandens kant.

En strømaftagende modstand er en modstand med lav værdi, der registrerer strømmen og omdanner den til en spænding. Den har normalt en meget lav modstand og minimerer derfor strømtab og spændingsfald. Dens modstandsværdi er normalt på milliohmskalaen. Denne type modstand svarer til almindelige elektriske modstande, men er designet til at måle strømmen i realtid.

Berøring af modstanden eller sonden med fingrene

Multimetre har også en særlig funktion, der registrerer de positive og negative ledninger på et batteri eller en strømforsyning. Ved at holde multimeterets sonde mod ledningen i et par sekunder kan du afgøre, om den strøm, der strømmer gennem den, er positiv eller negativ. Den røde sonde er forbundet til den positive batteripol eller ledning.

Når du bruger et multimeter til at måle modstanden, skal du sikre dig, at kredsløbet ikke er tændt. Ellers kan du få en unøjagtig måling. Husk, at modstanden ikke er så vigtig som at vide, hvordan den skal måles. Desuden kan den strøm, der løber i kredsløbet, beskadige multimeteret.

Test af kontinuitet mellem huller på et breadboard

Før du måler modstanden mellem hullerne på et breadboard, bør du først kontrollere breadboardets tilslutningsmuligheder. Testmetoden er kendt som kontinuitetskontrol og er en enkel måde at afgøre, om to forbindelser er kompatible. Brødkortet har huller med en metalfjederklemme under hvert hul. Tilslut proberne på dit multimeter til begge disse punkter. Hvis du har problemer med at finde en ledende vej mellem disse punkter, kan du sætte et par modstande på mellem brødbrættet og multimeteret.

Hvis du bruger et multimeter med en programmerbar funktion, kan du gøre det mere præcist ved at teste kontinuiteten mellem nogle få huller ad gangen. For at gøre dette skal du indsætte proberne i "+" og "-" kolonnerne på breadboardet og derefter måle modstanden på tværs af dem. Hvis modstanden er uendelig, så er de to rækker ikke forbundet.

Sådan kontrolleres PCB Board lodning defekter

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Sådan kontrolleres PCB Board lodning defekter

There are several common types of PCB soldering defects. These defects include pin holes and blow holes. Pin holes are small holes in a solder joint, while blow holes are larger holes. Both of these defects are caused by improper hand soldering. During the soldering process, the moisture in the board is heated and turned into gas, which escapes through the molten solder. When this happens, the board becomes void, and pin holes and blow holes form.

Common types of PCB soldering defects

Several common types of PCB soldering defects can be attributed to improper soldering techniques. These problems include uneven heating and uneven distribution of heat. This can result in solder melting unevenly and may cause component tombstoning. This problem can be avoided by using proper solder paste and reflowing the board in a proper temperature range.

Defects in the soldering process can ruin a beautiful PCB design. These defects are rarely the fault of the designer, and are more likely to be the result of a manufacturing error. Manufacturers should know how to spot these issues during the inspection phase. In many cases, the problem lies in the wave soldering process.

Another common defect is solder balling, which results in tiny balls of solder adhering to the laminate or conductor surface. PCB soldering techniques should avoid this type of problem. PCBs that have solder balls will look lumpy and dull.

Common causes

Soldering defects are common problems that arise during the production process of PCB boards. These defects can result in short circuits, open joints, or crossed signal lines. They can also be caused by variations in solder temperature and humidity. In addition, improperly applied solder can cause a lopsided surface and uneven soldering.

En af de mest almindelige årsager til PCB-fejl er varme og fugtighed. Forskellige materialer udvider sig og trækker sig sammen med forskellig hastighed, så konstant termisk stress kan svække loddeforbindelser og beskadige komponenter. Af denne grund skal højtydende PCB'er kunne bortlede varme.

Utilstrækkelig befugtning kan også føre til svage loddesamlinger. Lodning skal udføres på en ren overflade, og loddekolben skal have den rette varme. Hvis man ikke gør det, kan det resultere i en kold samling, som er klumpet og mangler bindingsevne.

Almindelige inspektionsmetoder

Der findes forskellige PCB-inspektionsmetoder, som bruges til at identificere defekter og sikre kvaliteten af elektroniske produkter. Disse metoder omfatter visuel inspektion og automatiseret testning. Disse tests udføres på flere stadier af PCB-monteringsprocessen. De kan opdage en række defekter, herunder åbne loddefuger, manglende eller forkerte komponenter og loddebroer.

Det første trin i identifikationen af loddefejl på printkort er at identificere komponenterne. For at gøre dette skal du tildele en referencedesignator, som er et bogstav efterfulgt af et tal. Hver komponent på et printkort har en unik referencebetegnelse. For eksempel betegnes en modstand med et R, mens en kondensator betegnes med et C. Disse bogstaver kan variere fra standardbogstaver, men de er en pålidelig måde at identificere komponenter på. Det næste trin er at vælge typen af inspektionstest. Det kan gøres ved hjælp af en AOI, ICT eller funktionstest.

En anden almindelig inspektionsmetode til printkort er røntgeninspektion. Denne teknik bruger en maskine, der gør det muligt at inspicere printkortet fra alle vinkler. I øjeblikket bruger PCBA123 et 2D-røntgeninspektionssystem, men planlægger at opgradere til en 3D AXI i den nærmeste fremtid.

Forebyggende foranstaltninger

Loddefejl på printkort kan være forårsaget af en række forskellige ting. Nogle problemer kan let identificeres, mens andre måske ikke er synlige. Den bedste måde at tjekke PCB-kort for disse fejl er at bruge et automatisk visuelt inspektionssystem. Automatiske inspektionssystemer kan f.eks. opdage defekter i loddesamlinger og kondensatorpolaritet.

En af de mest almindelige årsager til loddefejl på printplader er, at loddetinnet ikke er helt vådt. Det kan ske, når loddetinnet påføres for lidt varme eller efterlades for længe på printpladen. Et printkort, der ikke er ordentligt fugtet, kan føre til strukturelle problemer, og det vil påvirke printkortets samlede ydeevne. Der er dog flere forebyggende foranstaltninger, der kan træffes for at forbedre board wetting.

En anden årsag til loddefejl på printkort er forkert stencil-design. Når en stencil er forkert designet, kan det medføre, at loddekuglerne ikke formes helt. Brug af en korrekt stencil kan forhindre loddekugledefekter og sikre kredsløbets ydeevne.

Årsager til revner i PCB-harpiksmateriale under BGA-puder under SMTP-behandling

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Årsager til revner i PCB-harpiksmateriale under BGA-puder under SMTP-behandling

Revner i PCB-harpiksmateriale opstår på grund af indesluttet fugt. Årsagen til dette er en høj loddetemperatur, der resulterer i en stigning i damptrykket. Revnerne kan også opstå, fordi printkortets termiske udvidelse får afstanden mellem BGA-pads til at ændre sig. For at mindske risikoen for denne type fejl kan man bruge alternative pad-overflader, som reducerer den termiske påvirkning af tilstødende pakker.

Indespærret fugt forårsager revner i printkortets resinmateriale

Indesluttet fugt kan forårsage en lang række PCB-fejl, herunder delaminering, blærer og metalvandring. Det kan også ændre den dielektriske konstant og spredningsfaktoren, hvilket reducerer kredsløbets skiftehastighed. Fugt øger også stressniveauet i forskellige PCB-funktioner, herunder kobber og bga-pads. Det kan også føre til oxidering på kobberoverflader, hvilket reducerer overfladebehandlingens befugtningsevne. Derudover kan det øge forekomsten af elektriske kortslutninger og åbninger. Dette er især problematisk, fordi PCB-fremstilling involverer mange trin, der involverer brug af vand.

Under smt-behandling kan indesluttet fugt resultere i revner i PCB-harpiksmaterialet. På grund af dette bør PCB-producenter være opmærksomme på størrelsen af loddemaskeåbningen. Størrelsen skal være mindre end det ønskede landområde. Hvis SMD'ens pad-område er for stort, bliver det svært at føre loddekuglen.

Reflow-loddetemperaturer øger damptrykket

Forskellige faktorer kan påvirke pakkeforvridningen under BGA-lodning. Disse omfatter fortrinsvis opvarmning, skyggeeffekter og stærkt reflekterende overflader. Heldigvis kan reflow-processer med tvungen konvektion reducere disse effekter.

En høj reflow-temperatur kan føre til en forringelse af loddebulen. Temperaturstigningen kan føre til en reduktion i loddesamlingens højde, hvilket resulterer i en loddeafstand, der er mindre end den oprindelige højde på loddebumpet.

Formen på fastgørelsespuden er også en vigtig faktor for loddesamlingens robusthed. Det anbefales at bruge større og bredere pads end mindre. Det øgede areal øger risikoen for revner.

Klæbrig flux reducerer termisk påvirkning af tilstødende pakker

Tacky flux er et termohærdende materiale, der bruges ved samling af chipskala og flip chip-pakker. Dets sammensætning består af reaktive kemikalier, som opløses i underfill-materialet under reflow-opvarmning. Når det er hærdet, bliver tacky flux en del af netværksstrukturen i den endelige pakke.

Flux er et kemisk befugtningsmiddel, der letter loddeprocessen ved at reducere overfladespændingen i det smeltede loddetin, så det flyder mere frit. De kan påføres ved dypning, trykning eller pin-transfer. I mange tilfælde er de kompatible med epoxy underfill. Det gør dem i stand til at reducere den termiske påvirkning af tilstødende pakker under smt-behandling.

Brug af klæbrig flux reducerer den termiske påvirkning af tilstødende pakker under lodning. Denne metode har dog sine begrænsninger. Flere faktorer kan få fluxen til at svigte. Urenheder i fluxen kan forstyrre loddeprocessen og gøre loddesamlingen svag. Derudover kræver det dyrt udstyr at rengøre loddepastaen ordentligt før lodning.

Alternative overfladebehandlinger

Revnedannelsen på et printkort kan påvirkes af den anvendte pad-finish. Der er udviklet forskellige metoder til at løse dette problem. En af disse metoder er brugen af et organisk konserveringsmiddel mod lodning. Dette konserveringsmiddel er effektivt mod pad-oxidation. Derudover hjælper det med at opretholde loddesamlingens kvalitet.

Padgeometrien definerer printkortets stivhed. Den definerer også åbningen af loddemasken. Boardets tykkelse og de materialer, der bruges til at skabe hvert lag, påvirker boardets stivhed. Generelt er et pad-to-device-forhold på 1:1 optimalt.

Testmetoder til karakterisering af revner i pcb-harpiksmaterialer

Der findes forskellige testmetoder til at karakterisere PCB-resinmaterialers ydeevne under SMTP-behandling. Disse omfatter elektrisk karakterisering, ikke-destruktive metoder og test af fysiske egenskaber. I nogle tilfælde kan en kombination af disse tests bruges til at opdage pad cratering.

En testmetode til at identificere revner er at måle afstanden mellem stifterne. Typisk er 0,004 tommer acceptabelt for perifere pakker, og 0,008 tommer er acceptabelt for BGA-pakker. En anden testmetode til at karakterisere PCB-harpiksmateriale er at måle den termiske udvidelseskoefficient. Denne koefficient udtrykkes som ppm/grad Celsius.

En anden metode er flip chip-teknikken. Denne proces gør det muligt at fremstille flip chip BGA-substrater med høj densitet. Den bruges i vid udstrækning til avanceret IC-emballage. Flip chip-processen kræver en finish af høj kvalitet, som er ensartet og fri for urenheder for at kunne loddes. Det opnås typisk ved kemisk nikkelbelægning over kobberpuden og et tyndt lag nedsænket guld. Tykkelsen af ENIG-laget afhænger af PCB-samlingens levetid, men den er normalt omkring 5 um for nikkel og 0,05 um for guld.

Øger impedansstyringslinjen prisen på printkortet?

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Øger impedansstyringslinjen prisen på printkortet?

Impedanskontrol er en vigtig funktion, der påvirker printkortets ydeevne. Producenten kan styre impedansen på et printkort ved at justere konfigurationen af sporene og printkortmaterialets dielektriske konstant. Det er vigtigt for printkortdesignere at formidle deres impedanskrav på forhånd.

Impedansstyringslinje reducerer EMI-problemer

Brug af en impedansstyringsledning reducerer EMI-problemer ved at reducere den strøm, der kan flyde gennem en ledning. Som vi ved, jo højere strøm, jo højere emissioner. Men ved at bruge en impedansstyringslinje kan du reducere strømmen betydeligt til et niveau, der ikke vil forårsage problemer med dit udstyr.

Det øger omkostningerne

Hvis man tilføjer en Impedance Control Line (ICL) til et printkort, kan det øge prisen på kortet. Denne komponent er nødvendig for RF-produkter og bruger en flerlags FR-4-konstruktion. De pletterede gennemgående huller på ét lag forbinder spor på andre lag. Alternativt bruger komplekse strukturer nedgravede og blinde vias, som kun forbinder de indre lag. De dyreste ICL'er går gennem alle lag på printkortet.

Når du specificerer impedansstyringslinjen, skal du huske at være så detaljeret som muligt. Hvis du ikke gør det, kan fabrikanten blive nødt til at tage flere runder med designteamet for at bekræfte en kritisk specifikation. Det kan spilde værdifuld projekttid. Ved at give så mange detaljer som muligt kan du være med til at sikre et problemfrit og effektivt projekt. Desuden skal du huske, at kun én sporvidde er tilladt pr. PCB-lag, så det er vigtigt at specificere, hvilket tal du vil bruge.

Impedans er en vigtig parameter for printkort. Denne parameter varierer mellem 25 og 120 ohm i gennemsnit. Generelt er impedans en kombination af induktans og kapacitans, og den afhænger af frekvensen. I nogle digitale applikationer er det nødvendigt med kontrolleret impedans for at opretholde signalklarhed og dataintegritet.

Det påvirker kvaliteten

En impedansstyringslinje kan påvirke kvaliteten af et printkort på mange forskellige måder. Uoverensstemmende impedans kan forårsage refleksioner af signalbølger, hvilket resulterer i et signal, der ikke er en ren firkantbølge. Det kan forårsage elektromagnetisk interferens og lokal stråling, og det kan påvirke følsomme komponenter. Den korrekte impedansstyringslinje til et PCB-design er afgørende for PCB'ets pålidelighed.

For at få PCB af den bedste kvalitet skal du vælge en producent med et erfarent team af designere og ingeniører. Sørg for, at de følger kvalitetsstandarderne og leverer din ordre til tiden. Generelt anbefales det at bruge en producent med mindst 10 års erfaring. Nogle virksomheder tilbyder også tjenester til billigere priser.

Kontrolleret impedans er afgørende for printkort med højhastighedssignaler og enheder med høj effekt. PCB'er med kontrolleret impedans sikrer, at disse enheder fungerer som forventet, bruger mindre energi og holder længere. Når man designer et PCB, er det vigtigt at overveje impedansniveauet for kobberbaner. Hvis de ikke er afstemt, kan en enkelt refleksionspuls forstyrre et kredsløb og forplante sig til nabokomponenter.