Keywords: Express PCB

You can choose from either metallic or organic materials when creating surface finishes for printed circuit boards (PCBs) or Express PCB. It is simple enough to know which types of surface finishes exist, but how do you determine the best for your PCB? Each comes with its technical considerations, disadvantages, and benefits although they share similarities.

This article can help you learn more about three common types if you’re wondering how to select the right finishing technique Electroless Nickel Immersion Gold (ENIG), Organic Solderability Preservative (OSP), and Hot Air Solder Leveling (HASL).

Your Express PCB surface finishes significance

A significant impact on its quality and usefulness within its parent part will be offered by the surface finish you choose for your PCB. The copper layer of PCB is prevented from oxidizing by the finish, which would otherwise decrease its Solderability. Before the components are added, applying a finish that protects the board from oxidizing ensures that you can solder the additional elements as needed. Because of adequate copper conductivity, the PCB’s electrical connections rely on. It’s essential to adhere to the components as necessary and prevent oxidation.

On various factors, such as the quality of the final result, the PCB’s design, and the finishing process, selecting the appropriate finish will depend. For every PCB, Not all finish types are appropriate. When considering the different ones, below are a few characteristics to keep in mind:

Corrosion

To creep corrosion than others, some surface finishing types like silver can be more vulnerable. With essentially any type of finish you use, this kind of corrosion can occur but with immersion silver, it’s most common. It can cause short circuits due to interacting with neighboring features on the board as the corrosion of metal elements spreads along the PCB’s surface. As the use of lead-free finishes has increased, this issue has converted to a usual one. In offering resistance to corrosion, lead was effective.

In sulfur-rich and humid environments, Creep corrosion is also more common. Before settling on any one surface finish, consider what kind of settings your PCBs will be exposed to. In determining your products’ life cycles, the environment may have a major hand.

Time of Processing

For a specific finish, the processing window may be small or large — larger processing windows are offered by finishes like HASL.

On how complex the assembly is, the time the process takes depends. Some surface finishes like OSP can’t withstand numerous soldering processes and have limited thermal cycles. It will disappear after a few cycles and against oxidation, the PCB will lose its protection. However, during fabrication, an OSP surface finish for a PCB can be reworked. To immersion silver, the same applies.

ENIG takes longer to complete and is a more complex finishing process. For PCB production lines that don’t need to output a large number of PCBs in a short time, this makes it better to use.

Solderability

To create a PCB that will operate as intended, avoiding soldering issues is essential. To ensure a connection that functions adequately, Smooth surfaces are necessary within its given environment. Such as if it’s a layered technique or in the case of immersion tin like ENIG, consider whether the surface finish can solder directly to the copper.

Considering that different metals behave differently even in the same environments and require unique manufacturing techniques, Good wire bonding is also crucial. With each surface finish type being incompatible or compatible with these elements, wires may consist of materials like copper, aluminum, and gold.

Reliability

How efficiently the selected surface finish can bear its environment? You will want a finish that accommodates these if your PCB will need to meet specific reliability requirements. You should consider how high the cost of failure will be if the PCB’s finish fails to protect the surface and doesn’t work as intended although the cost is a major factor.

Under its TM-650 Test Methods Manual that details different ways, The IPC offers a set of standards to test PCBs for quality and reliability. These include techniques such as the amount of signal loss, chemical resistance, dimensional verification, and copper ductility. the effects these substances have on PCB dielectric materials is determined by one test that uses chemicals such as isopropanol and sulfuric acid.

Factors affecting the surface finish of your Express PCB

Which type of PCB finish you decide to use will be affected by a range of factors. As an integrated whole, it’s essential to consider all of these factors. Your finished PCB may not turn out as intended though they all hold weight within the process if you favor one characteristic greatly over the others. For example, because of its cost-effectiveness, you may choose lead-free HASL but later realize that as compared to other finishing processes, its co-planarity is lacking.

When investigating the various Express PCB surface finishes, below are some crucial components to keep in mind.

Cosmetics

To offer a better aesthetic value than ENIG, processes like OSP and HASL tend which another component is influencing which kind you choose. To creep similar issues, whiskers, and corrosion, do you need a shiny surface that’s less susceptible? Dealing with materials like silver and tin might be avoided by you. You may select options that don’t significant corrosion.

Volume

Which type of surface finishing do you use can be impacted significantly by Production volume. For example, after being deposited onto the copper PCB, a surface finish consisting of immersion tin will begin tarnishing soon. However, you can avoid tarnishing by using a high volume of PCBs. It may be better to go for a finish like immersion silver if you have a small batch.

Cost

The type you choose determines how much you spend on surface finishing. The cost of Finish quality is also a factor. As compared to ENIG types, HASL finishes are more affordable but they may not meet the precise quality standards you expect.

The board fabrication price will also matter. To select more advanced finishing methods such as ENIG; will there be room in your budget after the initial fabrication? To manufacture, Express PCB for industries like consumer electronics are less expensive decidedly. For higher-quality results, you can use more costly finishes.