Uncategorized – Nova Engineering

Tips and Considerations: Learn to Improve Your PCB Design Skills

mwcms on April 26, 2021

Are you a printed circuit board (PCB) engineer wondering how you can learn or improve your PCB design skill? Well, you are in the right place, as this post will give you a brief insight into tips and considerations that can help you polish your skills.

Most engineers are good at PCB designs. However, they lack some basic professional and personal skills they must master. You must begin with the basics and learn to practice your PCB designing skills with consistency day-in and day-out.

5 Tips to Improve Your PCB Design Skills

Here are five basic tips to improve your printed circuit board designing skills.

Learning more about the Layers

In case you wish to master the skills of designing a multi-layered PCB, you must have a clear understanding of printed circuit board layers. You must learn to revise your basics and learn about the latest standards and trends to ensure that your PCB design meets all the industry and global standards.

Remembering the Design Rules

There are numerous design rules that every PCB design engineer must follow. Some of the most essential ones are as follows.

Aim for noise reduction
Remember the EMI/EMC considerations
Remember the thermal integrity considerations, i.e., dissipation of heat because of the power circuits.
Remember the power integrity considerations, i.e., power loss in its path
Learn to design for test and add test points at several stages of design.
Follow the design for manufacturing ideology. Always consider track width, drill size, clearance, etc.

Learning to Use PCB Designing Software

As designing technology has evolved, using PCB design software is common. In case you are not good at using software, you must polish your skills to draw components, schematics, and printed circuit board layouts.

There are several PCB designing software solutions available in the market. However, you must pick a few that are common in your industry. If you are enthusiastic about learning more than one design software, then this will give you a competitive edge over other designers and engineers when searching for a new job.

3-D Modeling

While you learn to design a printed circuit board on software, do not forget to add a 3-D modeling feature into it. This will allow you to see an almost real depiction of your PCB design before manufacturing it.

Moreover, this will also allow you to detect any design errors and help save back-and-forth revisions with the PCB assemblers. This will translate into lower cost and time efficiency.

Learning to Review Thoroughly

So, you have learned the standards. You know the layers and know how to use software to create a 3D model of your printed circuit board. What is next?

You must always learn to improve your attention to detail. This is very critical if you wish to get your PCB design right the first time. This will again save you from a lot of hassle in the future because the tiniest flaw in the design may result in several revisions and sometimes the overhauling of the entire printed circuit board design.

Here, you can also learn about the basics of documentation and aesthetics. This will allow you not only to write how the components’ placement should be but also customize how the PCB design must feel and look.

The documentation part will allow you to clearly label where each component and connector must go and how it must look on the printed circuit board

The Take-Away

Learning all of the above skills will allow you to improve your PCB design skills as well as learn how to document the guidelines for the assemblers. The more elaborate you are in your design, the better the results. At Nova, we are always updating and improving our skills. Reach out for a consultation today.

PCB Finishes-Electroless Nickel Immersion Gold

mwcms on February 1, 2021

The perfect electronic device has to be light and small while offering the capability of maximum electronic functionality. The PCB industry has driven towards advanced packaging methods to meet this pre-requisite.

It involves increasing the integrated circuits’ density on a PCB board as well as combining several functionalities into a single dense package.

Electroless Nickel Immersion Gold (ENIG)

Electroless Nickel Immersion Gold is a twin layered metallic surface finish of 2 to 8 micro inch Au over 120 to 240 micro inches Nickel.

The Nickel here works as a barrier for the copper and provides a surface to which you can solder your components. The gold is responsible for protecting the nickel plating during storage time and offers low contact resistance, which is a requirement for thin gold deposits.

ENIG is undoubtedly one of the most used surface finishes in the PCB industry. It is all due to the implementation and growth of RoHS regulations.

Surface Finish Viable for Wire Bonding Process

While electrolytic nickel gold surface offers immaculate performance for gold wire bonding, it does suffer from three deficiencies. Each of these shortcomings causes a major roadblock for ENIG’s use as the leading surface finish application for circuit boards. Here are the three deficiencies.

The process is very expensive and usually requires a high gold thickness.
As you use higher gold thickness, your solder joint reliability may reduce drastically. It is because of the tin-gold inter-metallic formation.
The requirement of electrical bussing for establishing connections to the feature amidst the plating process will limit the densities of features you wish to achieve.

The limitations mentioned above also provide an opportunity for an Electroless process. These may include ENEG and ENEPIG that involves Electroless gold and Electroless palladium.

This surface finish has its own advantages, such as cost and packaging reliability. The cost especially becomes one of the most worrying aspects of the process. With a recent spike in gold price value, the price of this type of surface finish is becoming more difficult to control.

However, the cost of palladium metal is comparatively far lower than gold. Hence, manufacturers now have the option to replace gold with palladium for a cost-effective yet identical quality process.

ENIG is a commonly used surface finish that uses a nickel layer, which actually is a nickel-phosphorus alloy layer. This phosphorus content has two categories that are phosphorus nickel or high phosphorus nickel. The application of both is not the same.

There are certain advantages associated with Nickel, such as it is suitable or a lead-free soldering process. The surface it produces is flat, fine, and smooth. You can store it for longer periods considering the storage conditions are decent and not too harsh.

Additionally, Nickel is suitable for binding with aluminum and suitable for thick panels that can withstand attacks of several environmental elements.

Advantages and Disadvantages of ENIG

Here are some of the advantages and shortcomings of ENIG surface finishes.

Benefits

It produces flat surfaces
It offers completely lead-free surface finish for PCBs
It is good for Plated Through Holes (PTH)
It offers longer shelf life for the circuit boards

Drawback

This process is very costly due to the high gold prices in the market
The surface finish is non-reworkable
Black nickel and black-pad
The surface finish can cause damage to ET
The circuitry on the PCB may experience signal loss (RF)
The whole process of the ENIG surface finish is quite complicated

Nova Engineering is here to help you. Contact us today!

PCB Finishes – Lead-Free HASL

mwcms on January 19, 2021

LF Hot Air Solder Leveling or LF-HASL is identical to the standard HASL process. However, it does have an obvious difference, i.e., it does no use Tin and Lead Solder. Instead, you will use a Tin and Copper, Tin and Nickel, or Tin, Copper, and Nickel germanium.

This difference is what makes LF-HASL a cost-effective and RoHS compliant surface finish. However, similar to HASL, lead-free HASL is also not suitable for smaller components. For PCBs with smaller components, you can choose better surface finishes such as immersion coatings. They are a little more expensive but ideal for such purposes.

The lead-free HASL PCB surface finish became one of the most considered and frequently used surface finishes after immersion gold. It provided safer surface finish alternatives, but it never became the new standard and created a bit of hassle for the circuit board manufacturers.

The Complexity of LF HASL

It all came down to the complexity of applying LF-HASL finish, and some PCB manufacturers had to outsource this lead-free HASL solution.

The chemistry behind the composition of lead-free hot air solder leveling has evolved over the years, so have its applications. Both horizontal and vertical applications have issues identical to HASL, which are pooling and non-flat surface finish with a foggy appearance in certain areas of the printed circuit boards.

The pre-trial combination of lead-free HASL received bad reviews. The combination of using silver, tin, and copper alloy together originally produced poor results during processing levels. They left behind bumpy, uneven coats that appeared unattractive and dull, and demonstrated poor performance in PCB assembly.

However, removing the silver and changing the tin-copper along with a few tweaks to the manufacturing process showed improvements with smoother and better surface coatings than the initial results.

This promising development in the process and application increased the demand for the LF-HASL. Not only did it make LF-HASL a common practice but decreased the timeline related to customer product delivery.

LF-HASL Processing Challenges

Lead-free hot air solder leveling needs higher temperatures for its application. During the first pass, it leaves the surface dull and grainy. However, after the second pass, both the appearance and surfaces improve, displaying a flatter, shinier, smoother, and even coat on the circuit board.

That said- the exposure to excessive heat from dipping twice in the molten solution reduces the copper levels below the acceptable limit as per IPC standards. This shortcoming worked as a catalyst for another change to the process staining the lead-free hot air solder leveling surface finish.

After several changes to both chemistries and processes, LF-HASL is finally a stable PCB surface finish application. The new and improved process is finally capable of producing a consistent and quality surface finish using lead-free alloys. LF-HASL has drastically reduced the hassle experienced by the PCB manufacturers.

Why LF-HASL is Least Used?

You may wonder, after all those tweaks and improvements, what stopped LF-HASL from becoming the standard finish? Lead-Free HASL is still probably the least utilized PCB surface finish in the industry.

The reason is the introduction of other innovative surface finishes such as ENIG (Electroless Nickel Immersion Gold), OSP (Organic Solderability Preservative). Even immersion silver and tin took over surface finish landscape by storm.

LF-HASL Work in Progress

Although LF HASL has come a long way in terms of improved viability, it is still work in progress. It has to cover some groundwork to compete with other surface finishes. However, it is gaining popularity amongst consumers, prompting PCB manufacturers to consider using LF hot air solder leveling as a standard surface finish.

QFN Basics

mwcms on December 21, 2020

QFN is an acronym for the Quad Flat No-Lead package and is one of the most popular semiconductors used worldwide. There are four main reasons why.

Low cost
Small form factor
Good thermal performance
Impeccable electrical performance

Like other semiconductor packages, QFN’s function is to connect (both electrically and physically) silicon dies to a printed circuit board (PCB) via surface-mount technology.

QFN is a lead framed package, also known as chip-scale package or CSP, that has the ability to contact and view leads after assembly.

A QFN package typically uses a copper lead frame for PCB interconnection and a die assembly.

Single vs. Multiple Rows QFN

A QFN can have a single or multiple rows of pins; the single row structure forms either by a saw singulation or a punch singulation process.

Both of the processes mentioned above divide a large array of packages such as an 18” X 24” sheet into individual packages.

On the other hand, the multiple rows QFN relies on the etching process to realize the required number of pins and rows, which are then singulated using a saw.

At the bottom of the QFN package, there is an exposed thermal pad that you can solder directly to the PCB system for optimal heat transfer from the silicon die.

Benefits of Choosing the QFN

Some key benefits of using QFN are as follows:

Decrease lead inductance by using optimally short bonded wires
It is lightweight
Small size and thin profile, i.e., “near chip-scale” footprint
Having an exposed copper die is perfect for several applications with better performance needs
It uses a standard surface-mount flow and equipment for PCB assembly
It has no lead associated coplanarity issues

The Downsides

Not many, but there are certain downsides to adopting QFN packages, including:

Possible floatation of the DFN packages on the molten solder pool found under the thermal pad
An exposed chip contact pad may face oxidation problems

However, you can mitigate these issues by controlling the re-flow process better and using plated QFN packages (tin), which reduces the oxidization issues.

QFN Thermal Characteristics

A QFN package has an exposed pad that offers low heat resistance allowing it to transfer to your PCB. Therefore, it is highly suitable for soldering the exposed pad to large conductive surfaces like the GND plane.

QFN also allows adequate physical and electrical connection between the IC and the PCB.

QFN Electrical Characteristics

An exposed or thermal pad is an efficient means of drawing heat from a die to a PCB. QFN is thermally efficient, whereas the exposed pad is a cost-effective solution. QFN can handle anything between 2W – 3W without needing forced air cooling.

Other Names of QFN

Different manufacturers name these packages differently, such as Micro Lead Frames (MLF), and Flat no Lead (FL). Both of them are available with pads on two, as well as four sides.

Other names include Micro-Leadframe Package Dual (MLPD), Micro-Leadframe Package Micro (MLPM), and Micro-Leadframe Package Quad (MLPQ).

PCB Finishes: Immersion Silver

mwcms on December 7, 2020

It is a well-known fact that printed circuit boards (PCBs) use copper surface finishes as a common practice. If left unattended and unprotected, copper will deteriorate and oxidize, leaving your circuit board unusable.

A surface finish plays a vital role in creating an interface between a PCB and its components. Here are two of the main functions of a surface finish.

It helps protect the copper-based circuitry
It provides you surface that can facilitate soldering during the assembling process of soldering components to your PCB

What Is Immersion Silver?

Immersion silver surface finish is a type that you can apply directly over your printed circuit boards’ copper surface. This surface finish is most commonly used and ideal for metallic dome contacts, aluminum wire bonding, and EMI shielding.

The thickness of this material is between 5 micro-inches and 12 micro-inches, respectively. Additionally, immersion silver has lasting capabilities for at least a year.

Immersion silver surface finish does not react to copper the way Tin does. However, if you expose it to the air, it will tarnish; therefore, you must store the circuit boards with immersion silver finish in an anti-tarnishing packaging.

If you do everything right and store it in proper packaging, the PCB will still be solderable for 6 to 12 months. However, once you have removed your printed circuit board from the packaging, you must make sure that it goes through soldering re-flow within the next 24 hours.

In case you wish to achieve a higher shelf life than gold, plating is the most viable solution.

Benefits of Immersion Silver Surface Finish

PCBs always come with coated surface finishes. Adding a decent finish enables and ensures decent soldering capability, as well as it protects the copper circuitry of your circuit board from the outside air. There are several types of immersion finishes, such immersion tin, immersion gold, etc.; however, immersion silver is gaining popularity due to certain features it offers.

It is attracting a lot of attention from the PCB manufacturers. Here are some of the key advantages that declare it to be the preferred material for surface finishing in the circuit board industry.

It allows the proper spreading of solder on its surface, allowing better soldering of circuit board components.
Immersion is one of the RoHS compliant PCB surface finishes, and it is also environmentally friendly.
Compared to OSP “Organic Solderability Preservative” surface finish, the surface with immersion silver finish will demonstrate better resistance to several environmental aging factors.
The immersion silver is a material surface finish that comes with the capabilities to survive multiple re-flows.
Immersion silver has better and enhanced electrical properties.
It produces a flat surface and facilitates strengthened solder joints than HASL surface finish.
Immersion silver is immune to a phenomenon known as a black-pad interfacial fracture.

All of the advantages mentioned above make immersion silver surface finish an ideal choice for PCB manufacturers.

Choose Wisely

You must select an adequate surface finish for your PCBs. You can do so by considering several options while you factor material costs and performance requirements.

For instance, you are looking for an option that is lower in cost than Tin-Lead. HASL may sound like a more obvious choice, but it is not the most suitable option, especially when it comes to RoHS compliant products.

In case you are unsure of what type of surface finish you may need. You can always get help from third-party PCB fabrication services prior to making decisions you may regret later. A little bit of research will result in cost-effective and high-yielding design. We are here to answer any questions you may have and help you make the best decision for you. Contact us today!

Fab and Assembly Drawing Standards

mwcms on August 3, 2020

Both Fab and assembly drawings are useful to communicate various information to your vendors. The fabrication drawing contains information on how to build the printed circuit board (PCB). While your assembly drawing depicts details on how several components are going to fit on the raw PCB.

However, there are certain standards that you must follow, so your vendors can understand the instructions.

Basics of Fab and Assembly Drawings

First, whether it is a fabrication or assembly drawing, you will begin from the same place in both cases. Here are some general items you will need for both Fab and assembly drawings.

Board Outline

It is the outline for the design of your circuit board from a layout database. Typically, it includes cutouts and slots to define dimensions on your fabrication drawing. You will also use this outline to reference components on an assembly drawing.

Drawing Format

While some of the CAD systems may require you to utilize a library part as a drawing format, others will auto-generate a drawing format. It does not matter which of these methods your CAD system executes. You will have to combine this produced format with your PCB layout to build your drawing.

Identification Information

Usually, the drawing format will have one or multiple areas to add a drawing identification number, board name, revision level, contact data, creation date, and corporate address.

Now let us look at the specifics needed for both Fab and Assembly drawings.

Key Elements for Both Drawings

Elements for Fab Drawing

We will look at the fabrication drawing first. Here are some of the key features that you must include in your Fab drawing.

Drill Locations

Every hole in the board for vias or pars needs representation in your drawing. Your CAD system usually auto-generates these holes diagrams. However, your fabricator will be using the NC drill file sent for actual holes’ locations.

Hole Chart

This chart is also known as the drill schedule. It associates each hole size via using a unique drill symbol.

Board Layer Stackup

This one provides a cut-away view of your board with its layer structure. Pointers detail the width and configuration of all conductive layers on the board, including any associated core layers and prepreg.

Dimensions and Notes

Dimensions show the overall size of your board, along with different features within and around the board’s outline. The notes give specific instructions to the fabricator that it cannot include elsewhere.

Elements for Assembly Drawing

Let us look at what standards you must follow for an assembly drawing.

Component Outlines

It is best to display the shapes of all the components along with the reference designators for soldering onto your board. It also includes mechanical parts that will need press-fitting or attachment with mounting hardware.

Sometimes, these parts might not get accurate representation in the footprint library. So it may require a little drafting and drawing efforts from you.

Additional Views

These are usually required in double-sided boards as they need a view of both back and front. Both views are a part of one assembly drawing. You can also include expanded views with details of mechanical parts.

Manufacturing Labels

All manufacturing labels, including assembly tags and barcodes, will need identification via pointer and must have a reference in the assembly notes.

Assembly Notes

These entail manufacturing instructions, including industry specifications and standards, assembly details, and locations of special features. You can also add a list of all parts on the manufacturer’s request.

You can always modify or change the elements mentioned above for Fab and assembly drawings as per your requirement. Creating a checklist will ensure that you have not left out anything.

If you have any questions about the standards/elements that every Fab and assembly drawing must adhere to, we’re here to help. Reach out to us today!

BGAs – What Are They?

mwcms on July 17, 2020

What is a Ball Grid Array?

You may have heard the term BGA. Not sure what it means? We have you covered. BGA, short for ball grid array, is a specific type of surface mount technology (SMT). In most cases, BGA packages are used by professionals to mount different types of devices, like microprocessors, permanently. This is done by melting balls of solder between the circuit board and face of the device.

Did you know that a BGA can easily provide more interconnection pins than you can put on either a dual in-line or flat package? The great thing is that professionals can use the whole bottom surface of the device, instead of only the perimeter, and this is very convenient. The appearance of most ball grid arrays stems from people’s high expectations for modern electronic products with various functions, small size, high performance, and lightweight.

Also, it is worth noting that ball grid arrays comprise several overlapping layers. These have one to more than one million multiplexers, flip-flops, logic gates, or other circuits. Note that BGAs vary considerably. Certain BGAs, for example, have no connections in the center. In contrast, other BGAs have pins located all across the bottom of the package. Keep in mind that you can accomplish manual routing without creating any breakout pattern for simpler BGAs that have greater pitch and more space in the center of the BGA.

Alignment of Soldier Balls

Note that a ball grid array aligns its solder balls in a grid under the bottom surface of the connected device. This is unlike the dated perimeter-only package type that usually places soldering pins right along the edges of the device.

The benefit of this approach is that it leaves a significantly smaller or more compact footprint on the Printed Circuit Board (PCB), inducing better electrical and thermal properties compared to a conventional perimeter-style mounting package. You can imagine that the popularity of this format has considerably grown in line with the rapid miniaturization of electronics.

Benefits of BGAs

Makes the Most of PCB Space

Did you know that the use of BGA packaging usually means the involvement of fewer components? Also, note that smaller footprints can help save the space on most custom PCBs. And this is excellent as it highly improves the effectiveness of any PCB space.

Better Thermal Performance

This is another crucial benefit. The compact size of PCB based upon BGA packaging allows heat to be dissipated more quickly and easily.

Note that when you mount silicon wafer on top, then most of the heat can easily be transmitted down to the ball grids. And when you mount the silicon wafer at the bottom, then the back of that wafer is securely connected to the top of the packaging. And this is one of the most effective heat dissipation methods.

Reduces Costs

There is no doubt that the efficient and effective use of PCB space offers opportunities to save material and enhance thermoelectric performance at the same time. This is important as it helps ensure the overall quality of various electronic components and reduces the risk of defects.

Better Electrical Performance

The fantastic thing about BGA packaging is that it has no pins that can be broken or bent, which makes BGA packaging sufficiently stable so that you can ensure the electrical performance on a large scale.

Increasing Use of BGA

Using BGAs is very rational because it is quite straightforward, while other technologies have had their share of issues. For example, the traditional quad flat pack style packages featured very closely spaced and thin pins. And this configuration causes a number of serious difficulties. Some of them are as follows.

Damage

The pins on a Quad Flat Package (QFP) are very thin. This is why professionals have to control the positions of these pins very carefully. As a result, any mishandling is likely to lead to the displacement of these pins, and when it happens, they are very difficult to restore.

Soldering Process

Due to the extremely close spacing of these QFP pins, meticulous control of the soldering process is needed; otherwise, contacts may be easily bridged.

If you have any questions about using BGA’s in your design or how we work with them for your assembly please give us a call.