What is Hot Air Solder Leveling?
Hot Air Solder Leveling is a traditional printed circuit board exterior polish with a lengthy track record of performance. On Printed Circuit Boards, hot air solder leveling is a kind of treatment. A light coating of solder gets placed as a protective layer on the bare copper of a printed circuit board during the final surface procedure.
The printed circuit board will get immersed in molten material to achieve the HASL finish. All exposed copper surfaces will get covered with this solder. High-pressure hot air is pushed over the exterior via air knives after the solder gets retracted, which stages the solder layer and eliminates any residual solder from the panel surface.
Manufacturers acknowledged the PCB-HASL years ago. HASL ensures a strong solder bond and a long shelf life. Although HASL makes part soldering relatively efficient, the planarity of the exterior may be undesirable for fine-pitch elements owing to the depth of the HASL coating. A passivating mix of tin and lead makes up the HASL deposit. One of the benefits of hot air leveling is that it has long been the industry norm. If you choose to utilize a hot air solder leveling on your PCBs, you may count on a lot of industry expertise.
Another benefit of hot air solder leveling is how simple it is to do. Even individuals who are freshers in printed circuit board manufacturing can use it because it is straightforward. Hot air leveling circuit boards have a longer life span, which is one of the reasons it still gets utilized in circuit board manufacture. When it comes to employing the hot air solder leveling method, it’s crucial to evaluate the benefits and drawbacks of doing so.
Definition and Meaning of HASL
A light coating of soldering gets placed as a surface coating on the bare copper of a printed circuit board during the hot air solder leveling procedure. Following the application of the protective layer, the entire board gets immersed in molten solder, which binds to any accessible copper. The PCB is then withdrawn from the solder solution and blasted with hot air blades to eliminate any leftover layer, leaving a thin covering of solder attached to the exposed copper layer.
PCB-HASL is a new way! For many ages, a solder composition of around 63 percent Tin and 37 percent Lead is getting used for the HASL polish, but as demand for lead-free procedures has grown, “Lead-Free HASL” has become a popular option. HASL is the most cost-effective surface treatment, and most factories use it as the standard. The surface is rough, even though competent processes can apply a pretty homogeneous coating. There’s also a chance that the hot air blast won’t thoroughly clean the solder cover, resulting in pollution.
Steps for Applying HASL Coating
HASL, or Hot Air Solder Leveling, is a metal surface treatment process that gets applied to the PCB board’s topmost layer to preserve bare copper regions such as tracks until component installation and soldering get done. The HASL layer gets made up of solder with 63 percent tin and 37 percent lead, and it dissolves with the soldering substance throughout the assembly operation. The application of HASL coating may get done in three simple steps. If you want to be sure it’s flawless, read it carefully.
- The procedure begins with the absorption of the PCB board in a melted tin/lead mixture, which covers all accessible copper areas.
- Then, utilizing high-pressure hot air blades, a Hot Air Leveler (HAL) guarantees consistency of solder deposit by eliminating excess solder from the PCB board. The goal is to maintain a consistent and light coating on the board as possible.
- This layer serves as protection of the copper traces until the circuit is ready for installation.
The most common surface texture utilized in the business is HASL. Circuit boards get immersed in a melted pot containing a tin/lead mixture. Then the excessive solder is removed with ‘air knives,’ which blast hot air across the surface of the part.
A HASL surface texture is one of the more economical alternatives, with elevated solderability and the capacity to endure numerous temperature cycles. It was formerly the industry norm. However, it has now fallen out of conformity due to the Limitation of Hazardous Materials (RoHS) regulations. As a result, in the context of ecological and health implications, lead-free HASL has become the adequate solution. Although lead-free HASL has a longstanding experience in the business and is well-known among experts, it is completely safe to use and better satisfies the demands of regulations.
What are the Pros and Cons of Hot Air Solder Leveling?
The HASL finish is achieved by immersing the board into a tin-lead or tin-nickel solder and keeping it there for a period of time. After the PCB gets scraped, the extra finish gets eliminated using air knives, which are hot blasts of air. Although HASL finishing provides for a broad processing window, it can be affected by a number of issues, including symmetry and hence solderability. The level of the completion gets influenced by many things. Some of them are the direction of the air knives, pressurization, and the pace at which the PCB board enters and exits the solder. Here are some of the advantages and disadvantages of HASL.
- Pros
- One of the unforeseen perks of the HASL procedure is that it exposes the PCB to temperatures as high as 265°C, allowing any possible debonding concerns to get identified before any costly parts are mounted.
- HASL is a relatively low-cost approach when compared to other industrial methods.
- Because of its popularity and importance, HASL is widely available.
- Because it is the most prevalent finish, it is also the least costly, and producers are well familiar with it.
- Because the production method for Lead-Free HASL is almost identical to that for HASL, it has nearly identical benefits and drawbacks. Lead-Free HASL, on the other hand, is both ecologically benign and less costly than other lead-free finishing alternatives.
- Cons
- The discrepancy in width between big and small pads is a disadvantage, making it unsuitable for HDI PCBs or 20 mil spacing between SMTs and BGAs.
- Areas that are irregular and unsuitable for fine pitch parts
- Plated through holes that have been plugged or decreased in size
Lead-free HASL is comparable to regular HASL, with the exception that no tin-lead solder gets used. Tin-copper, tin-nickel, or tin-copper-nickel germanium can all get utilized. As a result, lead-free HASL is a cost-effective and RoHS-compliant option. It is not, however, suited for smaller and fine-pitch parts, as is normal HASL.
Call to Action
The process of inserting copper into a vat of boiling solder is known as hot air solder leveling (HASL or HAL). Before the solder hardens and relaxes, a succession of pressurised hot-air knives gets used to eliminate extra solder and even the surface quality. The results in a strong covering that shield the copper from rusting also makes the assembling procedure simple. Because of these advantages, HASL is one of the most widely used touch plating techniques today.
The cheapest method of PCB exterior polish is “Hot Air Solder Leveling.” It’s commonly accessible and inexpensive. A hot air knife gets used to balancing the board after it has gotten immersed in molten material. HASL can be beneficial if you’re employing through-hole or bigger SMT parts. It is not suitable. However, if your circuit will include SMT parts less than 0805 or SOIC. As the surface isn’t fully level, tiny parts may have problems. Tin-Lead solder often gets used. It signifies it does not comply with the RoHS directive.
You’ve probably gotten asked to choose between HASL and ENIG surface treatments if you’ve ever had a circuit board built legitimately. When all factors get examined, HASL has several characteristics that make it a top option. It’s no surprise that it’s well-liked by manufacturers.
Read more:-
