You have to go through the hard decision of choosing a matte finish or a glossy finish for your PCB. A glossy finish which terms as a shiny or glossy solder mask. PCBs operate well with both the Matter and glossy finish. Therefore it’s not that critical to choose. However, most of the time, people leave the choosing decision to the manufacturer. The manufacturer, by default, chooses the shiny finish.
What Is A Glossy Finish In Printed Circuit Boards?
A PCB glossy or shiny finish comprises a light-colored solder mask with a light-reflective feature as compared to a matte finish. It gives a poreless, softer appearance than the light appearance of a PCB matte finish.
What Is A Matte Finish In Printed Circuit Boards?
A Circuit board matte finish comprises a darker color solder mask with no shine at all as compared to a glossy finish. It gives a porous and softer look with no light-reflective feature.
When it comes to the standard of solder masks, both solder finishes of PCBs do not seem to have any different requirements. The advanced IPC-SM-840E Qualification and Performance of Permanent Solder Mask has its usage data.
The data mainly focuses on the testing of the material of the dry and liquid solder mask film, its usage on conventional PCBs, and makes it easy for the user, designer, and manufacturer to accomplish the fabrication process of the PCB. The type of finish you use does not affect the functionality of the board in any manner.
Advantages of a Glossy Finish
Most of the advantages of using a PCB finish mainly depend upon the aesthetic preferences of a designer. You can use a glossy PCB finish rather than a matte PCB finish due to the following reasons.
- The foremost reason is to give PCB a classic and aesthetic touch. Because many designers and manufacturers give PCB a glossy finish as a default, its shiny look gives PCB a modern touch.
- The second reason is to reduce the signs and symbols of wear with its light-reflective property.
- The last reason is its resistance to scratch. A glossy finish gives a harder surface to PCB, which relatively has a high rate of resistance toward scratch as compared to the matte finish of PCBs.
Advantages of a Matte Finish
The look of a PCB also determines which solder mask finish you will need for your PCB. A glossy one or a matte one. A matte PCB finish makes the process of fabrication much easier than a glossy finish. However, a skilled, professional fabricator gives a quality product no matter which solders finish he may use in the process. Some advantages of using a matter solder finish include the following:
- Firstly, it gives a visible look during the inspection of a PCB. A matte PCB finish does not possess any shine or lightning effect, which gives a visible look during the process of inspection. Therefore, this gives a fabricator a clear and visible appearance in the fabrication and assembly of PCB.
- It helps in detecting problems easily. A Matte PCB finish has a tendency to detect errors more readily and easily than a glossy PCB finish. Because of its visible nature, it makes it easier to look out for errors.
- It reduces the formation of solder balls. Many fabricators suggest that a PCB matte finish has less risk of forming solder balls. According to recent data, the lesser the glossy rate, the lesser the formation of solder balls.
Why Choose a Glossy Finish over Matte Finish?
The biggest distinction between a matte and glossy finish is simply the aesthetic look. Many people favor the glossy PCB finish as it looks much better. The glossy finish gives a shiny touch to PCB. They have light tones and reflect light. At the same time, the matte PCB finish gives a dark and dull look. The glossy finish makes the PCB harder, while the Matter PCB finish gives PCB a softer touch.
Matte finish can easily scratch and shows the finished residue over the PCB surface. At the same time, a glossy finish shows better scratches than a matte finish. If you want to make the first look of your PCB effective and tempting to the viewer, then go for a glossy finish. Although, just remember that the high reflectivity of light may cause a nuisance to the viewers during the fabrication process.
A buyer or a fabricator may use a glossy PCB finish instead of Matter PCB finish in some cases like:
- When your product appearance affects the marketing strategies, then go for a glossy touch as it increases the aesthetic vibes of PCB.
- Second, when you don’t know what to choose, then simply go for the glossy, shiny finish, as it serves as a default finish in the PCB industry.
Why Choose a Matte Finish over Glossy Finish?
Choosing a matte PCB finish does not lie in an efficient and cost-effective way, yet it does have a feature that makes it preferable over a glossy finish. This feature comprises solder balls of tin.
If solder balls concern your PCB manufacturing process, then choosing a matte PCB finish is an ideal choice. There are various factors that affect the formation of solder balls but surface roughness is one of them. The smoother and softer the surface, the more it balls up the solder.
As solder acts differently over smooth and rough surfaces.
On a rougher surface, the solder mask makes a convex form and reduces the solder ball area. Whereas on smoother surfaces, the solder tends to form fewer solder mask balls as compared to rougher surfaces. Well, as a glossy finish is used most of the time due to default, so this will not cause any issues.
Well, choosing a matte PCB finish may become ideal in situations like:
- When the accuracy and precision of products become your top priority, then choosing a matte PCB finish enables you to work freely as it becomes easy and visible to detect issues and errors due to high visibility.
- Second, when quality assurance concerns you, if you want to evaluate and inspect the PCB on your own, then matter finish helps you in finding errors rapidly and easily.
How to check whether the matte finish is used in designing the PCB?
The resistance of the solder layer determines which solder finish goes well while creating an ideal PCB layout. Most fabricators choose a glossy solder finish due to its default choice, which makes it a popular choice too.
Aesthetic stands as the main distinction between both solder finishes. A Matte finish appears dark and dull, while a glossy finish gives a light tone with the light reflective feature. The matte finish offers a softer look, while the glossy finish offers strong and hard finish touch. In the assembly of PCBs and manufacturing process, the solder finish does not bring any changes. It remains the same throughout the end. Although, it may affect the cost of the process a little bit.
The nature of scratches also brings the difference between the two finishes. Scratches remove easily in matte finishes because of the softer surface, while it becomes more evident in the glossy finish. Moreover, there may be visibility issues in the manufacturing process of PCB with a glossy solder finish due to its high light-reflectivity. During the glossy film installation, the optical network plays an important role in the removal of the film.
Causes of formation of solder ball
- The energy of the surface
- The Hardness of surface
- The temperature of the glass transition
- The type of flux
- The moisture level
- The roughness of the surface
The roughness of the surface plays a vital role in the solder ball formation. However, its real mechanism is still unknown. The solder mask on a rough surface and the solder mask finish on a smooth surface differ from each other.
Both are used as laminations and masks for several PCBs. On a rough surface, the molten solder forms a ball of convex shape, whereas it makes concave shape balls on a smoother surface. Both concave and convex surface lessens the areas of solder ball formation, which does not come in the matte finishes with a smoother surface.
Several studies on the level of gloss and its association with the defects of welding interpret that photo imaging gloss can affect the amount of the defects of welding in the PCBA soldering wave process. All these defects of weldings are directly correlated to the level of glow. Fewer gloss results in the lesser formation of solder balls. This process gets faster as compared to the number of welding bridges and short circuits. This means that if you want to eliminate or reduce the number of solder bridges or shorts, you need the lesser gloss, which reduces the formation of solder balls.
Select the Correct Color Finish For Your Printed Circuit Board
· Black
It’s difficult to handle the color black of a PCB. It leaves the contrast between traces, planes, and open areas negligible than other colors of solder masks. Moreover, it requires great magnification to observe the board keenly.
It becomes hard to inspect as it needs a slanted angle to make a shadow for observing traces. Moreover, it also creates an issue of heat absorption during the process of reflow. Furthermore, it requires great effort to clean the flux as it is already difficult to remove, which then needs further consideration in the black color case.
· Blue
The blue color of the solder mask seems the same as the blue hue of Arduino. It shows less contrast between the trace, planes, and open spaces as compared to green and red color PCB.
Blue color solder mask requires magnification for observing and evaluating the errors in the PCB. Remember that the blue color solder mask is ideal if the manufacturer does not need to match the color of the PCB with Arduino and is not concerned about showing traces off-board.
· White
If you think that a black color solder mask seems hard to manage, then you have not met a white color solder mask yet.
According to researchers, a white color solder mask does not seem very useful. White color PCBs have less contrast than black color PCB. The visibility does not improve even turning it towards the light.
· Yellow
Most engineers and designers do not choose yellow PCB. Yellow color solder mask shows high contrast between the planes, traces, and voids. It mostly resembles green.
Factors To Estimate When Choosing a Finish
The difference between the matte finish and glossy finish predicts where to use which finish. At this point, many of you are looking to find a suitable surface finish. Therefore, you must consider various factors while choosing it.
· Pad Flatness
As you know, some surface finish causes uneven and rough surfaces. This results in solderability impeding performance and some other factors. However, if flatness plays an important role in your PCB, then choose a finish that has even and thin layers. Finishes like OSP, ENEPIG, and ENIG fall in this category.
· Solderability & Wettability
Solderability plays a vital role in the manufacturing process of PCB. Some surface finishes cause solderability issues like ENEPIG and OSP. At the same time, a finish like HASL proves perfect for solderability.
· Gold & Aluminium Wire Bonding
If the PCB needs aluminum or gold wire bonding, then go for ENEPIG and ENIG finishes.
· Storage Conditions
Some surface finish improves the durability of the PCB, while some make it sensitive and fragile. Therefore, managing specifications and storage must be kept in mind beforehand while choosing the perfect surface finish for you. Surface finish like those which make PCB fragile must apply when handling requirements and risk-free storage meet with each other.
· Solder Cycles
Also, take into consideration the number of times a PCB goes through the soldering and reworking process. The majority of PCB surface finish is considered best for rework, while some do not fall appropriate for it, like immersion tin.
· ROHS Compliance
RoHS compliance plays an important role in choosing the PCB surface finish. Typically, some surface finishes which have lead in them are not appropriate for PCB RoHS compliance.
Conclusion
Both Glossy and matte finish have their own benefits and distinctions, which makes them apart from each other. These benefits and distinctions make them ideal and not ideal for various uses and applications. Ultimately, the ideal option goes for the fabrication of PCB.
It is difficult and challenging to choose the right and fit PCB surface finish. As it mainly affects the cost, quality, and durability of the PCB. However, depicting the needs and requirements of the product, the kind of components, the look, the level of aesthetics, and the reliability of the board makes it easier to choose the right surface finish for your PCB.
