If you have ever had a professional circuit board made, you were likely presented with a choice between ENIG and HASL surface finishes. These finishes differ in several ways, from their solderability to their cost. Although some manufacturers have a preferred option, you may be curious about the distinctions between these two.
HASL is a surface finish method that entails dipping copper in the pool of melt solder. The excess solder is then removed, and the finish is leveled using a set of compressed hot-air knives before the hardening of the solder. This technique results in a robust coating that shields the copper. It simplifies the assembly process and is widely used as a contact plating strategy due to its numerous advantages.
Although HASL is a great technique, it does have its drawbacks. PCB manufacturers commonly use ENIG as the gold plating strategy due to its numerous advantages over other ways. ENIG produces a much flatter surface, essential for properly adhering to big ball-grid packages. The absence of lead in the manufacturing process of ENIG boards enables a considerably cleaner, safer, and ecologically sustainable production process. Furthermore, eliminating the air knife step reduces the warping of boards. It is particularly when they are thin and enhances their thermal durability to some extent.
As a part of the production process, surface finishing is applied to PCBs to enhance their functionality, durability, and appearance. This process involves treating PCB surfaces using techniques such as coating, electroplating, and polishing.
Various surface finishes are commonly used in the manufacturing of PCBs, including:
- HASL (Hot Air Solder Leveling): The method entails submerging the PCB in a pool of liquefied solder and applying warm air to even out and refine the exterior.
- ENIG (Electroless Nickel Immersion Gold): In this technique, a fine coating of auto-catalytic nickel is administered onto the surface of the PCB, followed by a delicate layer of immersion gold. This surface treatment is renowned for its robustness and ability to withstand oxidation.
- OSP (Organic Solderability Preservatives): The procedure consists of administering a slim coating of the organic compound onto the surface of the printed circuit board to safeguard it from oxidation and enhance its solderability.
- Immersion Tin: The process of achieving a smooth surface texture for PCBs entails applying a tin coating that offers excellent protection against corrosion and reduces contact resistance.
- ENEPIG: This particular surface finish represents an upgraded variant of ENIG, featuring enhanced resistance against corrosion and outstanding shelf life.
- Immersion Silver: Coating the PCB with a coating of silver, akin to Immersion Tin, is the surface finish technique employed here, which endows the board with commendable resistance against corrosion.
- Gold Plating: The surface finish method employed here entails applying a layer of gold coating to the PCB, as the name implies.
When it comes to selecting the ideal surface finish for a particular application, several factors need to be taken into consideration. It includes the kinds of components utilized, the operating environment of the PCB, and the price analysis.
Moreover, solderability, cost-effectiveness, reliability, processability & compliance with lead-free needs are crucial factors that must be evaluated. Two commonly used surface finishes with excellent solderability are ENIG and HASL.
In lead-free appliances, compliance with RoHS and WEEE regulations for surface finish may be necessary for the printed circuit board.
What is HASL?
HASL is widely recognized as the most prevalent surface finishing technique employed in the production of PCB. This method entails submerging the PCB in a pool of melted solder, smoothed by hot air. This procedure is essential in creating an even surface finish on the printed circuit board, as it plays a critical role in ensuring appropriate soldering and stable component installation. The solder pool can consist of a combination of Tin and Lead, typically with a proportion of around 63 percent Tin and 37 percent Lead. However, if the lead-free PCB is desired, the HASL process can be slightly modified to accommodate this change.
Lead-free HASL contains approximately 99.3 % Tin & 0.6 % Copper. Despite being visually and functionally similar to Hot Air Solder Leveling, there are some differences in the production process. For instance, a lead-free Hot Air Solder Leveling alloy has a higher M.P. than lead solder, necessitating adjustments in the soldering process.
Despite its widespread use, HASL has certain drawbacks, including low reliability, high lead content in humidity environments, and the potential for inadequate soldering performance. The surface finish may also be uneven, rendering it unsuitable for high-density components and having poor shock resistance. Furthermore, plated via elements are unsuited for this finish surface.
HASL Finish
As mentioned earlier, there are two varieties of HASL surface finishes employed in the fabrication of PCBs: Lead-free Hot Air Solder Leveling & Lead-based Hot Air Solder Leveling.
- The Lead-based Hot Air Solder Leveling process is a traditional finishing method for printed circuit boards that involves molten solder containing lead. The resulting surface finish of the lead-based Hot Air Solder Leveling has a shiny and more reflective appearance.
- The lead-free Hot Air Solder Leveling process utilizes a tin-copper or tin-silver alloy for its finish, eliminating the use of lead. This alternative approach boasts superior reliability even in extreme temperature & humidity conditions.
Despite its long-standing use, HASL is replaced by more eco-friendly and dependable surface finishes, including Immersion Tin and ENIG.
What is ENIG?
In the manufacturing of printed circuit boards, ENIG serves as a surface finish method that involves electroless plating of a thin nickel layer. Unlike other plating processes, this chemical process doesn’t need external electrical input. The resulting coating offers a smooth foundation for the gold coating to stick to and exhibits remarkable resistance against corrosion. After the nickel layer has been applied through electroless plating, the board is submerged in gold plating for a process known as immersion plating. The immersion plating process deposits a layer of gold onto the nickel surface, which enhances the board’s electrical conductivity & minimizes contact resistance.
ENIG surface finish consists of a dual-layer metal surface comprising a nickel layer and a thin coating of gold. This finishing process is ideal for mounting components such as SMDs. The nickel layer ranges from four to seven um in thickness, while the gold layer ranges from 0.05-0.23 um. So this method conforms to the RoHS standards, making it an eco-friendly choice.
ENIG finish
ENIG is a cost-effective, lead-free solution that offers less contact resistance, corrosion resistance & strong adhesion, making it ideal for surface mount technologies. It boasts consistency and long life, making it a dependable choice.
1. Nickel & Gold, when combined, exhibit favorable resistance against corrosion, rendering them appropriate for electronic applications that endure challenging environmental conditions.
2. Having a layer of Gold atop Nickel results in excellent electrical conductivity & minimal contact resistance, critical for appropriate soldering and ensuring the stability of the components.
3. ENIG is a viable option for mounting devices & components, as it eliminates the need for a solder mask coating and offers a level surface for Surface-mount devices elements.
4. Applying ENP Gold results in a consistent and sleek surface texture on the PCB.
ENIG plating
The reliability of ENIG plating is questionable due to reported dependability problems. Plating often results in non-uniform wetting, separating copper traces from a finish. To ensure optimal performance, it is crucial to regularly replace the reductant. It contains Nickel ions to maintain the appropriate temperature & concentration levels of the coating.
Applications of ENIG
PCB manufacturing utilizes various surface finishes for different applications. Here are some examples.
- In printed circuit board manufacturing, surface finishing is essential for safeguarding the copper circuit on a board from oxidation. By coating the base surface of an exterior layer, the surface finish helps to protect the exposed copper circuitry.
- The procedure additionally furnishes a surface that can be soldered when assembling electrical components onto the PCB.
Advantages and disadvantages of ENIG vs. HASL
Using surface texture in PCB manufacturing offers numerous benefits. Here are some of the advantages.
- Ease of soldering: The application of ENIG or HASL as surface finishes results in a sleek surface on a PCB facilitating effective electronic assembly soldering.
- Corrosion resistance: Immersion tin surface finishing creates a layer that resists corrosion, safeguarding the PCB from harm, even in severe environments.
- Improved electrical performance: Surface finishing with immersion silver/OSP results in enhanced electrical performance of the PCB, accomplished by reducing the surface impedance.
- Enhanced appearance: By utilizing gold and other specialized plating techniques during surface finishing, a visually pleasing appearance can be achieved on the PCB.
- Low cost: OSP and HASL are the most commonly employed surface finishing methods in PCB manufacturing due to their cost-effectiveness.
Likewise, every surface finish technique has its drawbacks, but some general disadvantages are:
- Complicated system: Achieving a smooth surface finish on PCBs is a complicated task that calls for specialized equipment & expertise. As a result, the manufacturing process of PCBs may incur additional expenses and prolonged production time.
- Environmental problems: There is a need for various surface finishes to be made more eco-friendly. HASL, in particular, has the potential to emit toxic fumes during coating procedures, posing a threat to both workers & local community.
- Product shelf life: Using OSP as a coating for the PCB can result in a restricted shelf life & potential degradation of the board over time.
- Compatibility issues: It is important to note that not all surface textures are suitable for every type of PCB material & component. Hence, manufacturers must consider compatibility factors during the manufacturing stages.
- Application-specific downsides: The electrical properties of certain surface finishes, including impedance & loss tangent, make them unsuitable for high-frequency applications. Similarly, some surface textures can not be appropriate for heat-intensive applications owing to their thermal properties.
Major Differences – ENIG vs. HASL
Individuals in the PCB industry likely comprehend the purpose behind copper textures on the surface of PCBs. When left exposed, copper oxidizes and deteriorates, making the PCB unusable. While there are numerous forms of surface finishes available, it’s essential to understand their impact on the connection between the element & PCB.
Surface finishing serves two essential purposes in the PCB industry: protecting the copper circuit and facilitating the soldering process during the assembly of PCB components. To better understand PCB surface finishing, we will compare ENIG plating & HASL finish.
1. Cost Difference Between ENIG vs. HASL
Due to its affordability and sturdy composition, HASL has been a favored option for surface finishes across various applications. This prevalent surface finish is available in many variations. Its application process exposes the printed circuit board to temperatures as high as 265 degrees Celsius. It enables the identification of assembly issues before attaching any components to the board. These attributes make it an attractive choice for cost-conscious users.
In contrast to HASL, ENIG is comparatively more expensive due to the gold plating process and the utilization of multiple-layer boards. However, ENIG boasts impeccable corrosion resistance, rendering it suitable for aluminum wire bonding, high-density technology & advanced solderability. Opting for ENIG may be a wise investment as it offers a superior shelf-life and delivers optimal value for money.
2. ENIG vs. HASL Have Different Operation Steps
The Hot Air Solder Leveling process involves placing copper in the vessel of molten solder. It is followed by the use of hot-air blades to remove any surplus solder and refine the surface texture. Once the solder cools and solidifies, the outcome is a robust and dependable coating that safeguards copper against corrosion. This process is ideal for users seeking a simple assembly process and a durable coating.
In contrast, the Electroless Nickel Immersion Gold process is a gold immersion plating procedure exclusive to printed circuit board manufacturers. The outcome of this process is a smoother surface that facilitates the secure attachment of big BGA packages. Additionally, since ENIG plating doesn’t require a hot-air blade process, its circuit board exhibits superior thermal durability. However, the intricacies of the ENIG plating process may prove to be too challenging for users lacking in-depth knowledge of the production process.
3. ENIG vs. HASL Service Life
While HASL may appeal to those seeking to reduce expenses, manufacturers have recognized that it lacks the necessary durability. Due to the challenging soldering process required when attaching other printed circuit board components, it is unsuitable for minimal shock applications.
ENIG boasts a sturdy and long-lasting metallic coating consisting of nickel, fortified for added durability. To enhance accessibility in storage, a coating of gold is there to safeguard the nickel layer. Despite being pricier than HASL, ENIG offers outstanding electrical performance, a distinguishing feature that confers longer shelf life compared to alternative coating alternatives.
4. Surface Treatment Between ENIG vs. HASL
To succeed with the Hot Air Solder Leveling process, all layers of solder coating must exhibit a uniform, smooth, and bright surface with fewer defects.
However, the HASL method tends to produce coatings with poor smoothness due to its reliance on high temperatures. It may ultimately impact the performance of your PCB.
Additionally, the uneven finish that often results from the HASL process can limit the use of printed circuit boards that contain high-quality pitch components within their design.
ENIG provides a consistently smooth surface finish, attributed to its metallic coating comprising nickel. This coating not only adds a protective obstacle to a copper circuit but also safeguards the surfaces onto which components are soldered. Additionally, a gold layer acts as a protective shield during the storage process for a nickel.
5. Selection of Thin & Thick Plates
With HASL, board thickness can reach up to two hundred miles. However, since the procedure relies on onboard technology, it may cause slower electric conductions in certain cases.
ENIG’s plate is a favorable electrical connector due to its minimum gold thickness of five to fifteen inches, making it easy to solder. Additionally, its exceptional wear resistance allows for reliable rotary switches.
6. Difference Between ENIG vs. HASL Unleaded and Leaded
Different types of HASL are available, classified into two primary groups: lead-based & lead-free. However, most variants contain hazardous substances, including lead & toxic chemicals. It poses a potential risk to designers who work in a place without appropriate protective measures and ventilation. Thereby jeopardizing their health and safety.
ENIG is available in various versions, catering to the needs of both high-end and budget-conscious electricians. However, low-quality Electroless Nickel Immersion Gold variants may have insufficient nickel/gold plating, leading to “black pad” issues. Conversely, high-quality Electroless Nickel Immersion Gold plates use adequate amounts of nickel & gold coating to combat the negative effects of lead & emissions.
7. Differences in Bonding Strength Between ENIG vs. HASL Plating
Hand soldering is the most suitable method with HASL, as the joints tend to form quickly. If the soldering material is the same as the material useful in HASL. Then it’s important to have strong adhesion because the materials interact with each other at a very small molecular level. The bonding strength of HASL makes it highly dependable, especially for sleek finish applications.
ENIG boards undergo a uniform coating process using gold and nickel to get the proper bond. A new nickel layer solution is available with better properties that control the stability of the solution and reduce the brittleness of the nickel layer, resulting in better flexibility. Additionally, the new kind of immersion gold solution used in PCB immersion has a neutral PH value. It makes it cost-effective and corrosion-resistant.
8. Solderability & Corrosion Resistance
The HASL finish offers high solderability for a PCB, and its robustness allows for easy soldering and assembly during multi-step processes. However, the Hot Air Solder Leveling process involves submerging the whole printed circuit board. It can result in additional thermal pressure on the board.
With ENIG, the solder joint is between the Nickel layer and the solder. It’s crucial to avoid exceeding this layer to reach the copper. It’s also essential to dissolve the gold completely into the solder joint. The new immersion gold solution used in the process has exceptional oxidation resistance, protecting the copper.
Wrap Up!
It’s essential to compare the difference between ENIG and HASL when searching for a high-quality printed circuit board surface finish. HASL may be the best option for those seeking a low-budget finish.
However, for specific applications such as keypads, lead-free layers, and wire bonding with a through-hole plating solution, ENIG is the optimal choice.
Whether you need HASL/ ENIG surface coating for your PCB, look no further than RayPCB. Our focus isn’t solely on profit; rather, we prioritize ensuring that you receive the best value for your investment. With our tailored solutions, we offer a vast array of technologies to suit your specific needs. Don’t hesitate to contact us today to fulfill all your printed circuit board surface treatment needs.
