Contract Electronics Manufacturing and PCB Assembly Blog

A Printed Circuit Board, abbreviated as PCB is a foundation used in the design of electrical gadgets. It plays to important roles:

• Providing mechanical support to components in the design

• Electrically connection the components through conductive pathways

In the current electronic world, the leveraging of a PCB can result into a simple yet compressed electronic gadget design or the creation of Very High Scale Integration designs important in the creation of microcontrollers and processing units.

PCB assembly consists of a series of intricate steps that must be followed to the latter if the product is to be of any use in the electronic design and creation fraternity.

Readying the board that will eventually be the PCB

The preparation of the board and the type of material chosen for the board varies depending on the quality of product the designer desires to achieve. The first step is in the creation of the laminate, which is achieved by pressure curing layers of cloth or paper with thermoset resin to create a final uniformly thick panel.

The type of material used in the curing determines the laminate classification hence the job it can do. Characteristics considered in classification include fire resistance, dielectric constant, loss factor, shear strength and tensile strength.

Printing the circuit into the board (etching)

This is a dynamic step whose approach varies depending on the end product desired. Most PCB assembly procedures however cover the laminate with copper on both sides and then proceed to remove the copper from unwanted places resulting into the wanted fine copper traces. This method, referred to as subtractive method, is cheap to implement but more environment polluting than the more complex additive method.

Additive PCB assemblage procedure electroplates the copper traces onto the laminate to form the desired circuitry. Though it uses less copper and creates fewer residues, it comprises of several intricate steps making it a more complex approach in comparison to the subtractive approach.

Individual approach to the etching procedure

Whatever etching approach you decide to settle for, there also are other choices to make in the implementation mode. Major approaches are

• Large volume approach: This consists of the silkscreen printing approach, which is the main commercial approach and the photographic option used when fine line widths are needed.

• Small volume approach: This involves printing onto a see-through film and using a photo-mask along with photosensitized boards then etch, using laser resist ablation or using a CNC mill with a spade shaped cutter or tiny end mill to gauge off undesired copper from the laminate.

• Hobbyist approach: This uses Laser print resistance technology that laser prints onto a transparent layer before heat transferring it with iron or bespoke laminator onto exposed laminate and then touching it up with marker before etching it. Other approaches in this category are hard to achieve in mass productions.

Drilling holes into the PCB and adding circuit components

The next step is in drilling holes through which the components in the design have to go into. This is achieved by the use of tiny diameter drill bits prepared from coated tungsten carbide. To accomplish this, you have to use high-speed automatic drills to keep away from marring and tearing up the copper tracks.

The contact ends that have to remain open are coated with a viable solder composite to ensure that the PCB will remain conductive without suffering from problems of copper oxidation.

The best way out of the mayhem

It is clear to see that PCB assembling needs heavy investment in terms of expertise and infrastructure. To avoid wasting all this money in the creation of a system that might not end up being as productive as it should be, you might have to consider the option of outsourcing. Out sourcing complete builds for use in your activities could be the simplest and cheapest way out for your enterprise.

Transitioning to lead-free assembly electronics requires not only product reliability, but also the ability for an optimized assembly process. Additionally, material selection, component changes, and handling potential testing failures are integral to a successful transition. 

Choosing Materials

Surface finish is one of the key material choices impacting the entire assembly electronics process. The assembly process itself, plus the complexity of the board and its use environment, all make an impact on this decision. Typical options include lead-free HASL or ENIG, OSP, ImAg, and ImSN, with new innovations becoming market-ready all the time. Different laminates are often under-specified due to underestimating their quality during the assembly process. Alternatively, laminates may be over-specified, which commands a higher cost.

Solder alloys are another important decision: wave solder, surface mount, and solder for BGA balls all have to be considered. Typ[ically, SAC305 is the surface-mount alloy of choice, and it performs acceptably under most circumstances. Depending on the complexity required for your wave solder alloys, the most cost effective solution is SnCU, especially if you have thin boards with low-aspect holes that need to be filled. SnAgCuNi is preferable for more challenging holes, although this may depend on the surface finish and choice of flux as well. For board flexing capabilities, or withstanding shock events, a variety of lower modulus alloys like SAC105 are becoming more prevalent.

Component Qualifications and Testing

Early adopters of lead-free assembly electronics discovered frequent occurrences of melted plastic components on wave solder connectors. This lead to a switch away from nylon 66 toward the more appropriate nylon 46, or sometimes LCP. These meet the requirements of moisture and temperature sensitivity, a must-have in surface-mount LF components. 

Other components that need to withstand heat damage may be more difficult to detect, which makes preventing that damage a greater challenge. Electrolytes within electrolytic capacitors may boil if time limits and safety temperatures are exceeded, yet these limits are not always outlined in sufficient detail.

Common specs may offer some suggestions, yet without the necessary variables to predict possible behavior. Component engineers end up guessing at preheat durations and total peak heat, while attempts are made with lead-free alloys to properly fill holes under various conditions.

Testing the strain capability of separate components following lead-free assembly is another blind spot. For example, it’s commonly known that SAC alloys have a reduced tolerance for strain, yet their assembly manufacturing people rarely offer specific limits for these devices. If suppliers could record results of four-point bend testing for their components in order to determine an objective maximum strain capability, the user could know if problems are more likely to arise during component stuffing, performing ICT, or attaching their boards to the chassis.

Reworking

All too often, lead-free reworks are overlooked in favor or meeting tight manufacturing schedules. However, records indicate that reworking is one of the greatest challenges involved with making the transition to lead-free assembly. A Lead-free assembly electronic has a more difficult window lying between the cold solder on one end and heat damage at the other.

Reworking can bring operator-to-operator benefits to the mix, optimizing equipment process that was probably originally designed for Sn-Pb rework. Every critical component requires a strict rework process which must be rigidly adhered to. Extensive failure analysis has to be undertaken before a determination regarding appropriate rework procedure can be made. Damage to the PCB, the component itself, or any neighboring components must be prevented. New rework equipment may be necessary, as well as the employment of new shielding techniques. 

Implement Auditing

Despite the growing experience with assemblage of lead-free PCBs, high quality is not always maintained after high-volume production begins. A comprehensive audit plan should be in place to address with the supplier in order to ensure accountability.  Making the change to lead-free assembly electronics provides an excellent opportunity to review your supplier’s typical process, and make any necessary adjustments for optimum quality control.

Here's a question we get asked more often than we might otherwise expect: "Why do I need a PCB assembly service?"

Printed Circuit Board assembly is one of the mainstays of consumer electronics today, although that's only been the case for the last 30-40 years. Thanks to the development of surface mount technology and other advanced production techniques, it's now become more simple for most companies to outsource their jobs to a PCB assembly service than to do it in house.

None the less, it's good to review why things have developed this way. So let's take a look at some of the major reasons a manufacturer should look at using PCB assembly services to aid in their production.

The Advantages of a PCB Assembly Service

1. Doing it in-house requires a lot of expensive investments. It used to be that everyone did their own electronics manufacturing, but that requires a huge capital investment in production lines and equipment, not to mention manpower and expertise. For most companies, there's little foreseeable ROI on an investment like that, even looking years down the line.

2. Economies of scale work. Another primary benefit of outsourcing your PCB assembly is that allows you to leverage the investments other companies have made into production technology. A large, dedicated electronics assembly plant will be able to produce more units, more quickly, and at a lower cost than you could with your own facilities.

3. Design services are often part of the deal. While this isn't true of all PCB services, many offer design services to help you refine your designs. Expert PCB manufacturers can often engineer superior solutions and help you produce better products, and more cheaply.

4. True expertise. Most major electronics assembly companies have years or decades of experience in mass-producing electronics. That's expertise that would be incredibly costly if you went looking to a specialist to oversee your own operations, but comes relatively cheap when you go with an outsourced assembly firm.

5. Guaranteed quality control. Another major issue with self-assembly of electronics components is QC. On top of the production facilities, do you have the resources to also check and guarantee the quality of the PCBs that you produce? Top electronics manufacturers have extensive QC procedures and can provide top quality components.

And all this adds up to one key point:

If you don't trust the components, you can't trust the final product.

Any electronics company with any regards for its future has to consider its own reputation to be extremely important. People today can use the Internet to instantly research your company as well as all of your competitors. If you become known for putting out low-quality products, it can become a nearly insurmountable problem.

The best way to have reliable final products is to ensure that reliable components go into their manufacture. Besides improving your own products, this will also aid your engineers as well. After all, if something does go wrong, knowing that all your components were created to top-line specs will make it easier for them to find the actual source of the problem.

So, in short, why do you need a PCB assembly service? For the lower price, for the higher quality, and for the peace of mind that comes with putting out a reliable product. There is simply little reason today to do your own manufacturing in-house, and plenty of reason to look outside your company instead.

What convinced you to hire a PCB assembly service for the first time? Was it worth it?

While electronic board design is just as important during the creation and assembly manufacturing process of a circuit board, especially for printed circuit boards (PCBs), there are several other factors which must always be considered in order to save on cost and make your business at least some profit. Beyond making components which work, what else can a seller do in order to ensure that they can reduce the cost of their electronic circuit boards?

Size is everything

Consider the price of surface area for about anything. Bigger houses cost more, as do cars. The same can be said about even circuit boards--the bigger the area that needs to be designed and assembled, the higher of cost it will be to you. So, in order to keep the price low, make sure to keep the surface area to a minimum as well. Be considerate of designs for circuit boards.

However, going too small might also incur some higher fees, too. Very minimal boards which try to save on space as much as possible are only going to be problematic because the machinery will need a higher precision and the manufacturing process even longer. If anything, a electronic board design needs to be in a "sweet spot" of not too big and not too small.

Not only does size matter, but so does shape. Most circuit boards are cut into very easy shapes such as rectangles, because harder shapes can cost extra since a finer precision must be made in order to make sure everything fits accordingly.

Keep it simple on the board

While not all electronic board designs can be made as simple as possible, most of them these days should be. In order to keep your costs down, try to make sure that the actual physical dimensions for everything on the board, including copper pieces, have plenty of room for the assembly line to not worry about finer dimensions and precision. Think of it this way: the more packed in objects are on the board, the more you have to pay.

Actual components need to be simplified, too

Annular rings, copper objects, and other components of electronic PCBs will take up space on the board regardless, as they're meant to do so. But, if you want to make sure your manufacturing services bills stay at a reasonable number, remember to make sure that the components tend to be on a bigger side. This ensures that the machinery can work around all of the shapes of the components and won't have a higher risk of any faulty cuts or errors.

Everything should be consistent

Most orders, if not all, are going to be different in some shape or form for you. Still, the shape of the electronic board design once it is cut out along with everything else still matters--why would they mentioned if they weren't? Keeping all of your designs rather consistent means less specialized care, and avoiding higher costs, for you.

There are several other ways you can save on your electronic circuit boards, such as:

• Keep it as simple as possible design wise. Don't overdo it with extra margins that promise extra safety and prevent any failures, already have your own included in the design.

• Always stick to your guns about preferred materials, trying not to use "substitute" material that may be inferior quality and lose you more money in the end. Simply put, don't skimp on the materials!

• Don't forget to look up certifications of a manufacturer, it could potentially save you money in the long run if they're properly certified and have up-to-date equipment.

However, everything is up to your judgement when it comes to your own PCB designs. These are just some proven ways to consider spending less on manufacturing costs without losing the quality of your end product.

Do you know of more ways others can save on their PCB assembing Services?

Considerably different from dendrites or other such shapes in components, tin whiskers can pose a very serious problem for a circuit board and other types of technology if they happen to be found and identified correctly. Tin whiskers are structures of "crystalline" formations that resemble whiskers and are most commonly found in electroplated tin that is used a finish on components, including PCB.

Several different components of PC Board assembly utilize tin for coating, although some measures were made to prevent tin whiskers from forming. One way is to reintroduce lead into the market, which can help stabilize the finish, however the exposure to lead over a long period of time is still dangerous and most governments still ban its use. Because of this, most companies used special alloys.

Also, some industries are still allowed to use lead in their PCB assembly of technology components and there can be other ways to prevent tin whiskers without it that you can implement. But first, what are other ways these whiskers can form?

• Stresses from poorly formed components which do not fit well together.

• The use of intermetallic formation can also cause tin whiskers.

• Many different outside sources of stress can create tin whiskers to form, which means the entire area of the components need to be checked.

• Bending, stretching, or scratches from both external and internal problems are another big factor to consider when looking for tin whiskers.

Assembly is at most risk, which automatically means a faulty product if the whiskers begin to grow and interfere with the components. While tin whiskers may seem harmless enough, they pose a very real threat to the product as well as people. One of the most common problems from whiskers in PCB assembly is a short circuit or arcing. Electrical equipment can suffer shortages and even harm people from their arcing, which ultimately means lost time and money.

This impact on global PCB assembly means broken equipment, ruined circuity, and shoddy craftsmanship overall that needs to be addressed. In order to prevent or mitigate tin whisker formation, you can take these precautions:

• If at all possible, remember to avoid the use of pure tin plated coating and other equipment. Most companies utilize alloys to help stabilize the components to mitigate tin whiskers, but caution still needs to be advised.

• Simply replate the areas that are at high risk of whiskers by either outsourcing to a contract manufacturing company or attempting it in-house. However, it is highly advised that you use an outside manufacturer to help strip down the current plating and put on a newer plating to avoid tin whiskers.

• A foam encapsulating coat or housing can be applied to whisker prone areas, helping prevent any problems in the future. However, it entirely depends on the type of foam encapsulating coat used, how much of it is applied, and how dangerous the whisker prone area is. Fortunately, however, this normally helps prevent short circuits in most cases.

• Alternatively, you can try to relieve any stress to the area with a hot oil reflow or new soldering job.

Working with a reliable assembly manufacturer who is willing to help with any tin whisker problems is also a very highly recommended route. Most are certified to make sure that no pure tin components are used whatsoever and instead alloys are used to mitigate whisker formation. There is always the risk of faulty and counterfeit parts which could also cause tin whiskers, but working with US-based companies normally means a higher standard of quality overall.

Remember, tin whiskers are much different than dendrites and cause serious damage to circuity! Simply ignoring the issue can result in failures in the components with short circuiting and arcing.

Have you ever experienced tin whiskers in your PCB components? What mitigation measures were put in place?