Mikä on galvaanisen korroosion vaikutus piirilevyyn?

If you’ve ever wondered what is the impact of galvanic corrosion to a PCB, you’re not alone. This type of corrosion causes neighboring traces to become contaminated by a solution or ionic liquid, and small slivers grow between the traces. These slivers can cause short circuits or even disable a functional block on the PCB. If the corrosion affects the power lines on the PCB, you could experience a whole device malfunction.

Examples of galvanic corrosion on a PCB

Galvanic corrosion is an electrochemical process whereby the surface of one metal reacts with the surface of another metal. This reaction takes place in the presence of an electrolyte, and it usually occurs between dissimilar metals. In primary cells, this process is exploited to create useful voltage.

The corrosion process begins when moisture, or ionic liquid, contacts an exposed metal part. Upon contact, metal oxides begin to grow and cause the surface to corrode. This process can also affect adjacent circuit boards, causing short circuits and deterioration of the entire board.

One way to minimize galvanic corrosion is to use corrosion inhibitors. These are effective at reducing galvanic potential, but require constant monitoring. They also increase the conductivity of water. So, it’s important to properly maintain the PCB when working with it.

Another method for preventing galvanic corrosion is to use antioxidant paste between copper and aluminum electrical connections. This paste consists of metal with a lower electro potential than copper. This will help to ensure that metals do not come into contact with each other and minimize the chance of galvanic corrosion.

Galvanic corrosion is often a result of dissimilar metals used in soldering joints. Because of this, it’s crucial to choose the right material for mating connectors. Materials with the same ionic potential are more likely to resist corrosion than those with dissimilar metals.

Process for reducing galvanic corrosion degree on a PCB

The degree of galvanic corrosion on a PCB board can be reduced in various ways. The first technique involves analyzing the network and finding the causes of galvanic corrosion, and the second technique involves increasing the area of the organic coating process (OSP) disk in the network.

The copper pads on a PCB are protected by a surface finish, but moisture can enter under the finish. Once inside, moisture reacts with the copper and starts a corrosion process. This process can then spread along the trace. In many cases, galvanic corrosion occurs due to contact between two dissimilar metals, such as copper on a PCB and the metal of a component. The presence of a corrosive electrolyte also increases the chance of galvanic corrosion.

Galvanic corrosion is a common problem in electronics, particularly in high-speed applications. It happens when two dissimilar metals are in contact with an electrolyte. When two dissimilar metals are in electrical contact, the more reactive metal atoms lose electrons and cause oxidation. This leads to a short circuit.

Keeping PCBs clean is critical to their longevity and ensure the longevity of the devices. The prevention of corrosion starts with keeping them dry and free of liquids. As a result, PCB manufacturers and designers must carefully protect their boards against moisture beading on exposed conductors.

Typical corrosion failure types in electronics

Typical galvanic corrosion failure types in electronic devices occur due to different types of processes. One of them is the formation of a water film on the PCBA, which can lead to leakage currents and a wrong output signal from the electronic device. Another type of corrosion failure is caused by a defect in the manufacturing process. This corrosion type often results in a short circuit in the switch.

The rate of corrosion depends on several factors, including temperature and the surrounding environment. The presence of moisture, dew, or condensation will accelerate the process. The presence of dust particles will also increase the corrosion rate because they retain moisture. Dust particles come from a variety of sources, including soil/sand, smoke, soot particles, and salts.

Stainless steel and zinc are examples of noble and active materials. The higher the relative difference between the two metals, the greater the amount of force that will be exerted during galvanic corrosion. A cathode with a large surface area will corrode at a high rate due to the high current.

Galvanic corrosion is a major concern in industrial design. Magnesium is a highly active structural metal. It is used in the aerospace and auto industries. The area ratio of the cathode and anode will also affect the amount of current produced by galvanic corrosion. Insulation spacers between two metals may also reduce the risk of galvanic corrosion by changing the distance between them.

Methods For Detecting PCB Failures

There are several ways to detect PCB failures. Among these methods are X-rays, Slice analysis, and Optical microscopy. Each of these methods is useful for identifying and assessing the extent of PCB damage. However, not all of these methods are suitable for every PCB failure. For example, electrostatic discharge damage is difficult to detect. It affects components by softening the solder and causing multiple shorts. In order to avoid this problem, the manufacturing process must be monitored minutely.

X-rays

PCB X-rays are a useful tool for detecting PCB failures. These images can reveal problems such as voids and solder traces. These problems can occur due to escaping gases or overheating of solder.

Slice analysis

Slice analysis is a method used to analyze the microstructure of PCBs. It can help detect a wide variety of PCB failures. Slice analysis involves cutting the PCB into vertical and horizontal sections and examining their cross-sectional characteristics. It can identify many different PCB failures, such as delamination, bursting, and poor wetting. This information can be useful for quality control in the future.

Optical microscopy

Optical microscopy can be an effective method for detecting PCB failures. It provides detailed images of the failure sites, and it can be used to detect nonconformities and identify contamination sources. The method is also useful in documenting samples as they are received.

ALT

The ALT method for PCB failure detection is a more direct approach to measuring solder joints and solder paste deposition. This technology uses a laser beam to scan a PCB assembly and measure reflectivity of various components. The measured value is then compared to a board’s standard specifications to determine if there are any faults.

Micro-infrared analysis

PCB failures are typically caused by defects on the solder joints. By determining the cause of the defect, manufacturers can take necessary steps to prevent recurrence. These measures may include eliminating solder paste contamination, making sure that the PCB has the correct aspect ratio, and minimizing PCB reflow time. There are a variety of methods used to analyze PCB failures, ranging from simple electrical measurements to analyzing sample cross-sections under a microscope.

ALT measures solder joint deposition

ALT (Aligned Light Transmitter) is a newer technology for measuring the height and shape of solder joints and solder paste deposition on PCBs. This technology is more precise and allows for a fast measurement. The ALT system uses multiple light sources, such as cameras or programmable LEDs, to illuminate the solder joint components. The amount of light reflected from each component is measured using the power of the beam. However, secondary reflection can cause an error in measurement, since the beam may reflect from more than one position.

Sähköstaattinen purkaus

The Electrostatic Discharge (ESD) method is used to detect PCB failures. An ESD is the result of extreme electrical stress, which can cause catastrophic failure and hidden damage. It can occur for a variety of reasons, including high current density, an increased electric field gradient, and localized heat formation. The resulting damage is hard to detect and can cause major product failures. PCB assemblies are most susceptible to ESD when they are in contact with other charge-carrying objects.

Exclusive Layout Tips For BGA Chips

To layout a BGA chip, you should understand its footprint. There are several different types of layouts. You can choose from Vias, Fanouts, and Fiducial marks. The datasheet for the NCP161 chip provides the recommended pad size and shape.

Fanouts

If you’re designing a PCB with BGA chips, it is important to consider the best routing pattern for your part. A high pin-count BGA chip, for example, requires meticulous planning to achieve the right escape routing patterns. You’ll need to take into account factors such as the component’s pitch and the desired spacing between its balls.

The best route for a BGA chip consists of two basic steps. First, you should calculate the number of layers needed to route the signal pins. There are two basic routes you can use for your BGA: a traditional fanout, or a dog-bone fanout. Typically, the dog-bone fanout method is used for larger-pitch BGAs. It allows you to route the outer two rows of pins on the surface layer, while leaving the remaining inner pads free of vias.

Fiducial marks

BGA chips are widely used in electronic assembly. However, because of their peculiar shape, they present a higher risk of short circuits during soldering. The right layout tips and practices can help you avoid these problems. In this article, you will learn how to correctly place BGA chips on your PCB in order to maximize the soldering effect.

The first step in proper BGA chip layout is to ensure the proper spacing of the components. Usually, the pads are not numbered sequentially but rather in a column-row format. The columns are numbered from left to right, starting with A1. Pin A1 is typically indicated by a mark on the top side of the chip.

Corner marks

When it comes to PCB layout, the same rules apply whether you’re working with BGA chips or other types of electronic components. The best way to achieve optimum performance is to make sure that your BGAs are mounted with a powerful X-ray system. You should also use a vision placement system to ensure that your BGAs are positioned correctly.

When working with high-pin-count BGA chips, planning is key. You may need to add several board layers to accommodate all the escape routing. You must also carefully consider the placement of components before you begin routing the traces.

Power integrity

High-pin-count BGA chips require careful planning before routing traces. You should also take into account the routing channels required for vias that exit the pins. In some cases, it may be necessary to add two additional board layers to accommodate the extra pins. Moreover, BGAs have multiple rows and columns, which requires careful placement of components.

The first step is to decide where to place the BGAs. Some designers use flip-chip BGAs, in which some pins are removed from the interior rows. Others use microvias, which are drilled by laser. Blind vias are also an option, but they are more expensive. Blind vias are usually included in the most expensive layout plans.

Mitä eroa on Hasl Lead Free- ja Hasl Lead Free -materiaalien välillä?

HASL on tina-lyijyseos. Se muodostaa helposti liitoksia, ja sitä käytetään usein käsinjuotossa. Sen vahvat liitokset ovat mahdollisia näiden kahden metallin tiiviin molekyylisidoksen ansiosta. Tämän vuoksi se on suositeltava viimeistely korkean luotettavuuden sovelluksissa.

HASL on tina-lyijyseos

HASL on tinan ja lyijyn seos, jota käytetään usein elektronisissa piirilevyissä. Se muodostaa helposti lujia liitoksia, ja sitä käytetään yleisesti käsin juottamiseen. Kaksi HASL-tyyppiä ovat samankaltaisia ja ovat vuorovaikutuksessa molekyylitasolla. Nämä samankaltaisuudet tekevät HASL:stä erinomaisen valinnan korkean luotettavuuden sovelluksiin.

Tina-lyijyjuotteella on useita ainutlaatuisia ominaisuuksia. Tina-lyijyjuotteen kemiallisia ja fysikaalisia ominaisuuksia on tutkittu laajasti viimeisten 50 vuoden aikana.

Se on ohuempi

Lyijyttömillä piirilevyillä on useita etuja HASL:ään verrattuna. Näistä eduista HASL:llä on paras säilyvyys. Lisäksi lyijyttömät piirilevyt ovat paremmin levitettävissä. Tämän vuoksi ne soveltuvat paremmin kuparin juottamiseen. Lyijyttömillä piirilevyillä on kuitenkin useita haittoja.

Lyijytön HASL on ohuempaa ja sen koplanaarisuus on parempi kuin lyijy-lyijy HASL:n. Ero juotospinnoitteen paksuudessa on noin puolet lyijy-lyijy-viimeistelystä. Lyijyttömällä HASL:llä on korkeampi sulamispiste, ja se edellyttää juotosprosessin lievää mukauttamista. Prosessi on samanlainen kuin tavallinen HASL, mutta siinä käytetään erityistä juotosvirtaa. Tämä juoksute auttaa aktivoimaan piirilevyn kuparipinnan. Kun juote levitetään levylle, on tärkeää, että sen paksuus on tasainen. Ilmaveitsi on tärkeä väline tässä prosessissa.

Se on yhtenäisempi

Elektroniikkateollisuudessa vuonna 2006 alkaneen lyijytöntä juottamista koskevan liikkeen jälkeen lyijyttömästä juottamisesta on tullut suosittu menetelmä piirilevyjen kokoonpanossa. Ennen lyijytöntä valmistusta tätä menetelmää pidettiin vanhentuneena tekniikkana. Se oli kuitenkin vallitseva viimeistelymenetelmä Pohjois-Amerikassa, Euroopassa ja Japania lukuun ottamatta Aasiassa. Tätä menetelmää pidetään nykyään ensisijaisena menetelmänä lyijyttömässä tuotannossa. Useat kiinalaiset piirilevyjä valmistavat tehtaat ovat asentaneet lyijyttömiä HASL-linjoja vastatakseen Euroopan kasvavaan kysyntään. Lyijytön HASL on kasvattamassa suosiotaan myös Intiassa ja Kaakkois-Aasiassa.

Lyijytön metalliseos on ihmisille paljon vähemmän myrkyllistä kuin HASL-versio. Sen eutektinen lämpötila on noin kaksisataaseitsemänkymmentä astetta, mikä on huomattavasti alhaisempi kuin HASL:n lyijytön seos. Lisäksi sen mekaaninen lujuus ja kirkkaus ovat korkeammat kuin lyijy-tinaseoksella varustetun vastineensa. Lyijyttömyyteen liittyy kuitenkin joitakin haittoja, kuten sen korkeammat kustannukset.

Sen säilyvyysaika on pidempi

Haslin lyijyttömän juotteen säilyvyysaika on pidempi kuin lyijyjuotteen. Se on myös halvempaa ja sitä voidaan muokata. Sillä ei kuitenkaan saada aikaan tasaista pintaa, eikä se ole luotettava hienojakoisissa sovelluksissa. Se aiheuttaa myös juotosilloja levyn varrelle, mikä johtaa epätasaisempaan kiinnityspintaan. Toinen vaihtoehto on upotustinajuotos. Se on valkoista metallista ainetta, joka levitetään suoraan kupariin. Nämä kaksi metallia vetävät toisiaan puoleensa.

Lyijyttömällä juotteella on pidempi säilyvyysaika kuin tinalyijyllä, mutta sillä on muutamia haittoja. Tinalyijy on myrkyllistä ja voi aiheuttaa ympäristölle haittaa. Lyijytön juote on ympäristöystävällisempi. Se on myös helpompi puhdistaa. Toisin kuin lyijypohjainen juote, Haslin lyijytön juote on yhteensopiva useimpien vaihtoehtoisten viimeistelyjen kanssa.

Se on RoHS-yhteensopiva

HASL:n lyijytön versio on samanlainen kuin perinteinen HASL-piirilevy, mutta siinä ei käytetä tina-lyijyä tuotantoprosessissa. Se on RoHS-vaatimusten mukainen vaihtoehto, mutta se ei ehkä sovellu erittäin pienille osille, kuten pienille LEDeille.

Lyijyttömän HASL:n lämpötila-alue on korkeampi, 260-270 °C, mikä voi aiheuttaa vääriä tuloksia ja levyn vikaantumisen. Lyijytön HASL ei myöskään ole yhtä tehokas SMD/BGA-komponenteille, joiden elementtiväli on alle 20 mm. Lisäksi LF HASL on epätasaisempaa kuin HASL Pb/Sn. Se voi myös aiheuttaa oikosulkuja, jotka johtuvat levitysprosessin aikana vapautuvista lyijyttömistä höyryistä.