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PCB Surface Finishes & Its Types: Choose the Right for Your Project

By Mer-Mar Electronics | Date posted: | Last updated: November 4, 2022
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When it comes to designing a printed circuit board, an important step is to be able to choose the right surface finish. There are a whole lot of factors that go into your choice of surface finish, including but not restricted to the components being used, what kind of production volumes you are looking at, the cost aspect and more. Here are 5 PCB surface finishes types that you can choose from along with their relative merits & demerits:

PCB Surface Finish Types

1. Hot Air Solder Leveling (HASL)

When cost is a major criterion, this is the finish to go with, as it is one of the least expensive options. What this finish involves is dipping the board in molten solder and then using a hot air knife to level it. This option works particularly well if you are using through-hole PCB or SMT components, even though it isn’t suited for SMT components smaller than 0805. Also, this surface finish isn’t RoHS compliant as it uses tin-lead.

Advantage of HASL PCB Surface Finish

  • It comes at a low cost
  • It is known for its solderability

Disadvantage of HASL PCB Surface Finish

  • It isn’t RoHS complaint
  • Not suitable for small components
  • Not suitable for HDI products

2. Lead-Free HASL

This surface finish is similar to the Hot Air Solder Leveling finish, except that it does not use tin-lead. What it uses instead is tin-nickel or tin-copper or even tin-copper-nickel-germanium. This makes it RoHS Complaint.

Advantage of Lead-free HASL Surface Finish

  • High solderability
  • Low on cost
  • Allowing large processing window.

Disadvantage of Lead-free HASL Surface Finish

  • It isn’t suitable for small components
  • There is a difference in thickness between large and small pads
  • It needs a high processing temperature

3. Immersion Tin (ISn)

Unlike the previous surface finishes, these work well for PCB small components. It uses a flat immersion coating that doesn’t come in the way of small components. Also, since tin isn’t expensive, this works well on the cost front as well. The disadvantage of this surface type however includes tarnishing. This is turn means that you need to solder the joints within 30 days. Alternatively, you could also use an immersion silver coating. However, this may be possible if the volumes aren’t too high. The advantages of this surface finish therefore are:

Advantage of Immersion Tin Surface Finish

  • It works for small components
  • It is not too high in cost
  • Has high solderability
  • Is re-workable

Disadvantage of Immersion Tin Surface Finish

  • It needs to be handled with care
  • Exposed tin can corrode
  • Baking prior isn’t advisable
  • Peel-able masks need to be avoided
  • Isn’t advisable for multiple assembly processes

4. Immersion Silver (IAg)

With Immersion silver not reacting with copper like tin, it can be a good alternative for the surface finish. However, it is still known to tarnish on exposure to air. With immersion silver PCB surface finish, an anti-tarnish packaging is of essence so that it remains solderable for 6-12 months.

Advantage of Immersion Silver Surface Finish

  • It works well for small components
  • It is mid-range in terms of cost

Disadvantage of Immersion Silver Surface Finish

  • It has to be handled sensitively
  • It needs anti-tarnish packaging
  • Peel-able masks aren’t recommended to be used.

5. Electro less Nickel Immersion Gold (ENIG)

This surface finish essentially involves having a thin gold layer over nickel. The components are actually soldered to the nickel surface. The gold layer lands up protecting the nickel. This makes for durability and a long shelf life. ENIG is these days the most used surface finish on account of this as also the fact that it is RoHS Compliant. Of course, its terms of cost, this finish does take a beating as it is one of the most expensive.

Advantage of Electro less Nickel Immersion Gold Surface Finish

  • It is suitable for small parts
  • The added advantage of this is that it is Wire bondable
  • Long shelf life
  • It is also good for Plated through holes

Disadvantage of Electro less Nickel Immersion Gold Surface Finish

  • Expensive
  • It can be aggressive when it comes to solder masks
  • Not re workable

Making the right choice

Choosing the right surface finish therefore requires a close evaluation of various factors including your production volume. You would also need to take into account factors such as:

  • Durability
  • Environmental Impact
  • Types of components

You will have to take multiple issues into account while making the final choice. For example, a cost-based approach may see you leaning towards tin-lead HASL. However, this has issues in terms of not being RoHS compliant. An experienced PCB Fabricator can go a long way in studying your requirements and recommending an option that best fits your bespoke requirements.

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The requirement of PCB panelization in PCB manufacturing!

By Mer-Mar Electronics | Date posted: | Last updated: November 30, 2022
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There is no doubt about the fact that PCB assembly is an extremely complex task that needs the highest degree of skill and efficiency. One thing that goes a long way in aiding the process is to use panelization.

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What Is Panelization?

PCB Panelization means grouping together of boards, which in turn aids the processing speed. Panelization is particularly common in the case of high volume as well as quick turn orders when optimization is of particular essence. With smaller boards connected together it becomes far easier for them to go past the assembly line. The boards can later be easily removed.

How Panelization in PCB Works?

The process of panelization typically works as follows. The first step involves the fabricator building blank boards. In the next step, the designer arranges these boards on to a larger board. The number of layers can exceed as many as 42 depending on how intricate the circuit is. It is easier if the boards are of regular shapes as odd shapes can make the layering process difficult. The array is then processed as one consolidated panel. What it means is that machines can fix components to boards easily.

However, it is important to take into account the following:

  • Array strength: Typically, an increase in board count in each array adds to the overall strength.
  • Layout: It is important to take into account the location of sensitive components towards the edge.
  • Shape: It is ideal if you are dealing with rectangular shapes.
  • Tooling holes: Arrays can often provide tooling holes’ spaces for automated testing.

Advantages of PCB Panelization

With PCB Panelization, production efficiency is significantly improved. Some of the advantages of panelization include:

  • Mass production – It is especially helpful in mass production where it optimizes time & money
  • Safety– Assembly often involves a lot of vibration. This is something that panelization protects the PCB from.
  • Speed – With multiple boards being processed at once, speed is a given. Whether it refers to soldering or testing the process becomes much faster

Some of the restrictions on panelization, however, include the fact that it isn’t too useful for low-volume PCB fabrication. Also, panelization is limited by factors such as:

  • Board thickness
  • Component weight
  • Space between boards

To ensure panel efficiency:

  • Boards should be of similar size
  • By and large the parameters of the board must be similar
  • There should be a similar copper distribution

PCB Panelization Methods

There are different ways in which panelization can be done:

1. V-groove Panelization

This involves making a V shaped line between boards and is useful when there are no overhanging parts

2. Breakaway Tab

This is a method of perforation between the individual boards.

V-Groove Vs Tab Routing – Best Panelization Method

Choosing whether you should use V-score or a tab routing method depends largely on the design.

  • Shapes: Typically, V scoring works well for regular shapes while tab routing works for unusual shapes.
  • Edge Components: For components placed close to an edge, tab routing may work better than v-scoring.
  • Edge Quality: Again, in terms of edge quality, tab routing is preferable
  • Time: V-scoring works better from the point of view of the time required.
  • Waste: In terms of material waste, V scoring is preferable as it reduces waste material and thereby leads to lower overall costs per board

PCB Panelization Guidelines

Here are some broad guidelines to be followed for panelization:

  • For routed rectangular panels with sides greater than 1.00”, 100 mil needs to be added between PCBs along with a 400-mil border on the outside. However, in case the length is less, 300 mil needs to be added between PCBs
  • For non-rectangular PCBs, 300 mil space needs to be added.
  • In the case of V-scoring, a 0-mil space needs to be kept between the PCB board edge and the traces with 300 mil on the opposite sides.

However, there are some exceptions to the thumb rules above:

  • To ensure that de-panelization does not result in damaging the component, the border between the PCBs needs to include the overhang distance.
  • To add to the mechanical strength of the panel in case of a heavy component, additional material needs to be added between the boards.

Another thumb rule to be followed is that the clearance between the metal and PCB board needs to be 5 mil in case of routing. In case of V-scoring, however, it needs to be as much as 20 mil.

Also, in the case of using breakout tabs, it is the size and shape of the board that needs to determine how many breaks out tabs should be used.

PCB Depaneling

Once the assembly and testing are done, the next step is the reverse of panelization or depanelization. Depending on the panelization method chosen, depanelization or separating into different parts can be done in many ways. Some of these include:

PCB Panel Separation Methods

  • Breaking by hand
  • Cutting along the V Grooves
  • Saw cut
  • Laser Cut
  • Punching out of boards etc

To sum up, it is imperative that the boards be designed with panelization in mind. This will ensure that you have to deal with minimal delays as well as take away the need for too many redesigns.

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The role of IOT in PCB Manufacturing business

By Mer-Mar Electronics | Date posted: | Last updated: December 24, 2021
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With electronic devices becoming ubiquitous in today’s world, what has also become ubiquitous in its presence is the emergence of a new phenomenon called “Internet of things”. It is not without reason that that IOT has been called the fourth Industrial Revolution.

In fact, the core of all electronic devices, IoT, is today revolutionizing PCB-driven devices. Here are only few examples of this revolution:

  • Smart home devices– A whole lot of smart home devices today are driven by PCBs. Whether they are computer systems or wall mounted tablets, IoT has a significant role in all these PCB based applications.
  • Automotive: Whether it is the use of an electric car or a bullet train, the importance of IoT in the automotive sector cannot be over emphasized.
  • Fitness trackers: Many wearable apps that use advanced versions of PCB such as Flex PCBs and HDI PCBs are powered by IoT technologies.

In each case, PCBs are at the crux of these devices enabling the use of IoT. It is the use of PCB that enables revolutionary ideas to come to life such as navigating real time traffic through the use of GPS devices.

With the use of Flex & HDI PCBs, it is possible to overcome the design limitations that make the PCBs suitable for IoT. Some of the advantages of such PCBs include:

Reduced size:

Unlike rigid PCBs, flex PCBs allow both a reduced size as well as dense circuitry.

Light weight:

Reduced size also comes with the advantage of light weight which in turn makes the device far more portable and versatile.

Improved Durability:

Flex PCB Materials also add to the device’s durability and its ability to stand up to harsh conditions.

Improved wiring:

With simplified wiring that eliminates mechanical connectors, it becomes an asset for IoT functions.

Cost effectiveness

With reduced need for layering, smaller sizes and more these PCBs also come at cost effective price points.

IoT PCB Design Tips

In designing a PCB that is ideal for IOT use, a number of key design areas need to, however, be kept in mind. Here are some areas to watch out for:

  • Size- With devices becoming progressively smaller, PCB designers do not have the luxury of space. HDI & Flex boards therefore have a very important role to play. IoT product designers also need to play a very important role in the designing phase itself.

 

  • Non-traditional materials- Ever so often non-traditional materials such as mesh or plastic may have to be employed for improved functionality as also to ensure that the design elements are incorporated. Clearly then, the days when square shaped PCBs were the industry standard are long over.

 

  • Adapting for the human body- In case the IoT product is one that is a wearable, it is imperative to ensure that the mechanics are such that they aren’t affected by the human body temperature. Similarly, there are issues of radiation and humidity. Moisture, for example, can totally impact the circuit and needs to be planned for. A package that is fully sealed and moisture resistant can well be the answer. You could also apply a conformal coating that doesn’t allow moisture to percolate.

 

  • Consumption of power- With IoT comes the need of an improved battery life. Power consumption thus needs to be planned carefully and testing needs to be done meticulously. In fact, each circuit block on the PCB needs to be allotted its power budget so that over all power budgets can be minutely planned. Having different validations for standby, Rx etc can go a long way in impacting usage of battery.

 

  • Reliability- Designs also need to be tested for reliability as there is increased pressure on the fact that devices need to stand the test of time when it comes to durability.

 

  • Wireless connectivity – The right wireless modules and RF circuit components need to be used. Also in choosing these parts, the power consumption as well as network range and speed needs to be factored in. Basis a number of different factors, one or several of the protocols mentioned below, will need to be employed.

 

In case of infrastructure, protocols such as RPL or 6LowPAN may need to be employed. For Identification, EPC or URIs may need to be put in use. Communication and transport will have to rely on Bluetooth or WiFi. Similarly for Data, Websocket or Node may need to be used.

All the above factors necessitate the fact that there is proper communication during the design stage as also the need for meticulous testing.

Going forward while the demand of IoT will only increase, what needs to be seen is that whether some amount of standardization can be brought into the process. While needs many be individualistic, it is a possibility that some design protocols can be standardized. The interface of PCB & IoT is really in the initial stages and a lot of their interaction remains to be seen. What is a given, however, is that demand is only likely to rise.

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What Is Silkscreen in PCB, Its Types, & Issues Associated with It?

By Mer-Mar Electronics | Date posted: | Last updated: August 31, 2022
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When it comes to PCB Manufacturing, the importance of Silkscreens cannot be overstated. Not only does it contain valuable information about the location of components, but it also contains other indispensable information such as identifiers, labels, and more.

So, what is the pure definition of silkscreen in PCB?

What Is Silkscreen In PCB?

An effective silkscreen is a layer of ink trace that acts as an efficient map with the right calibrations and information of various essential components such as logos, symbols, PCB components, marks, test points, etc. The role of PCB silk screening is important to

  • Identify circuitry including testing points, interconnections, and more
  • Parts identification
  • Safety precautions such as high voltage
  • Rating verifications and more.

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3 Types of Silk Screen Printing Technology

1. Manual Screen-printing

This is typically used when the line width is greater than 7mil and registration tolerance is 5 mil. From the accuracy point of view, however, this isn’t the most desirable choice as the output is determined by aspects such as the viscosity of the ink, humidity, pressure of the stroke, and more.

2. Liquid Photo Imaging (LPI)

This is used when the line width is more than 4mil. In terms of accuracy, this turns out to be more accurate than manual printing, even though the approach is time intensive.

3. Direct Legend Printing (DLP)

In terms of accuracy, this method is rated the highest. It is also faster than LPI, even though it comes at a higher cost.

While the importance of Silkscreen is undisputed, what also comes in its wake are several potential issues, which if not taken care of can lead to costly errors.

Commonly faced Silkscreen Issue

1. Components not represented correctly

Any small error in the silkscreen and its intended components, their shape, location, polarity indicators, etc can lead to a whole lot of issues for the technicians when they are doing any modification or a debug.

2. non-Readability

Another commonly faced issue is to do with the legibility of the silkscreen text. Using a very small font size or too narrow or too wide a line width are all potential causes of unreadability.

3. Wrongly Placed Reference Designators

Another common mistake that leads to error and a lot of angst among technicians, is to do with erroneously placed reference designators. In testing the board, technicians then have to grapple with the issue of the schematic not matching the board. The other issue with reference designators often has to do with dense designs, where reference designators are hidden by assembled components.

4. Split Silkscreen Ink

Ever so often the silkscreen ink can cover the surface mount pins and can cause damage to the board.

To avoid these common errors, the design guidelines must be followed carefully. Whether it is to do with font sizes or line widths, do stick to the specifications. Communication with the fabricator and understanding the requirements in detail will also go a long way in ensuring that manufacturing errors are minimized if not eradicated.

Doing some common hygiene checks including checking to see if the reference indicators are in place and that all fonts are readable, will ensure that the technicians do not face any issues too. Other checks such as ensuring that silkscreen clearances are fine will also reduce the chances of error.

Other important aspects that an experienced silk screen manufacturer will follow, include:

  • Marking using standard colors and larger shapes
  • Allow for common printing errors in fixing the distance on the board.
  • Adding extra marks to show the orientation of components on the circuit board
  • Placing polarity marks to reduce component orientation mistakes during board assembly
  • Measurement marks of pins and lines

Choosing the right silkscreen manufacturer, therefore, who has a strong learning curve is imperative to the success of the PCB Assembly. Going with a manufacturer who has extensive experience can save you both valuable time as well as costly errors.

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