TIPS AND TRICKS TO USE LEAD (PB) FREE SOLDERING

The electronics manufacturing industry is changing, taking the world towards an eco-friendlier and sustainable future. The new initiatives of adopting lead-free solder in place of the conventional leaded alloys is a bold move, yes, but the sheer benefits it will generate for preserving the health and wellness of our natural environment definitely outweigh the challenges posed by this switch. By following certain tips and tricks, you can always make use of lead-free soldering alloys with your existing circuit board manufacturing tech and hardware to create good quality solder joints. Here are some points for you to follow:

Heat requirements

Whether your process involves hand soldering or machine soldering of components on your circuit board, the first and most important factor for you to take into consideration is the heat resistance threshold of all elements involved. You should make sure that your soldering iron, circuit substrate and electronic components – all can take increased heating temperatures (typically 70-110°F higher than leaded solder) necessary to make the lead-free solder a liquid. If not, the extended temperatures and longer dwell time might end up damaging these surfaces irreparably.

Suitable liquid soldering flux

Lead-free soldering necessitates that the flux used to clean, de-oxidize and decontaminate surfaces before carrying out the soldering process should also be capable of dealing with the higher temperatures involved. The flux shouldn’t burn or turn corrosive and damage the components on the circuit board. In most cases, liquid soldering flux with chloride compounds are considered to be most preferable and suitable for lead-free alloys.

Different aesthetics

Lead-free solder joints look substantially different from those created using leaded alloys. These joints will look duller and coarser as compared to their counterparts, but that doesn’t mean that they are lacking in strength, durability, resilience or performance matters. Take some time to understand its properties, both aesthetical and otherwise, before you decide to rework a joint.

Patience, patience, patience…

Lead-free solder behaves differently from its leaded alternative. It will take a longer time to achieve requisite flow consistency owing to its higher melting temperature. Its dwell time will also be significantly longer. Rushing the soldering process will only result in the creation of weak and unreliable joints with the alloy. Patience is the key here and you will need time to adjust your understanding of the soldering process in accordance with this new lead-free alloy. Take your time to understand before moving ahead.

HOW TO AVOID SOLDER BALLS AND BRIDGING DEFECTS DURING THE SMT REFLOW PROCESS

Solder balling and bridging are some of the most common defects that occur in the SMT assembly process carried out using solder reflow. In most cases, these issues are caused as a result of flaws in the PCB assembly operations or poor understanding of materials involved in the manufacturing process. This blog post explains some of the reasons for solder ball creation and bridging defects, and explores different corrective actions that can be taken to resolve these issues.

Solder Balls

Solder balls are usually created due to air or water vapor that may be left trapped in the solder paste. When this air/vapor escapes too quickly, it may take a small amount of liquid solder from the joint to create a ball like structure that violates the minimum electrical clearance principle.

Corrective Action for preventing solder balls:

•    Manage the solder reflow profile by increasing the pre-heating temperature of the PCB so that the flux evaporates properly before solder paste application.

•    Tweak the pad size for the PCB in accordance with your operational recommendations to prevent space that may trap air inside.

•    Manage solder flux application to prevent excessive amounts being plastered onto the board.

•    Bake the PCB before beginning the SMT printing and reflow process.

•    Ensure that the thickness of the copper plating holes on the PCB is greater than 25μm to prevent water from getting trapped inside.

Solder Bridging

Solder paste may form unwanted connections on the circuit surface if it flows abnormally and unexpectedly on the board. These connections usually connect adjacent surfaces, thereby making a conductive path which may eventually ruin the circuitry. This defect is known as solder bridging.

Corrective Action for preventing solder balls:

•    Add a solder mask between adjacent pads and surfaces to prevent abnormal flow of solder paste.

•    Tweak the design of the PCB stencil and change hole-aperture to better control solder paste application.

•    Avoid old and new flux being used together in a single application

•    Adjust the pressure of solder paste printing as well as the pick-and-place nozzle to prevent splashing.

•    Ensure there is a zero print gap between the PCB and the stencil.

Hope these inputs will help you in getting better results from your SMT reflow processes. If you are still experiencing solder balls or bridging defects in your PCBs, make sure you consult an expert for corrective action.

GOOD OR BAD: SOLDER BALLS ON A PCB

PCB manufacturing process follows a specific progression of steps that have to be executed perfectly in order to create reliable and electrically viable joints using solder paste. However, certain process flaws and inadvertent errors may lead towards creation of random small spherical particle-like shapes in or away from the main solder pool after the reflow process is complete. These spheres are known as solder balls. While some manufacturers may choose to ignore such an occurrence, the IPC A 610 standard deems a PCB with more than 5 solder balls (<=0.13mm) within 600mm^2 as defective. This is because solder balls that have a diameter of 0.13mm or within 0.13mm of traces can adversely impact the reliability of a PCB since they violate the minimum electrical clearance principle. So, the answer to the question of whether solder balls on a PCB are good or bad is clear – they are definitely bad.

Formation of solder balls in reflow or wave soldering operations is generally the result of uneven solder particle melt which may happen because of the presence of an oxide layer or improperly wetted surfaces. The creation of these balls can be random, non-random or may be to the result of a solder splash back. Trapped air or water vapor inside or below the surface of solder paste may try to escape when the circuit board is heated to get the paste to flow. When this happens, the air ends up creating a bubble like structure while taking some amount of solder paste from the surrounding surfaces. This spherical shape usually has a void inside where the solder paste hasn’t been able to reach. This occurrence can have an adverse effect on the reliability and functioning of the circuit board.

Considering these factors, it is important to analyze your PCB assembly process and find out the root cause behind the creation of solder balls. This analysis will help you determine the actual problem that needs to be corrected to prevent solder balls from forming. Consulting an expert organization like Alpha Assembly Solutions can help you in determining defect causes, from conveyor speed to surface contamination, and find cost effective ways to correct the same.

So don’t let solder balls hamper the quality of your PCB product. Go ahead and seek expert assistance to combat this issue today!

WHAT IS SOLDER DROSS AND BENEFITS OF RECYCLING IT?

With the growing need for sustainable manufacturing practices, industries are looking to reduce their dependence on scarce natural resources and attempting to optimize existing processes for better use of materials being consumed. This trend towards eco-friendly operations has also touched upon the electronics manufacturing industry where changes are being made to ensure proper utilization of solder metals being used and prevent wastage from occurring. This is how solder dross and the benefits derived from recycling it have come to light.

What is solder dross?

Wave soldering processes are usually carried out in the presence of air, owing to which there are always chances of the metal alloy being rendered unusable because of oxidation. This unusable alloy is known as solder dross which is usually thrown away as process waste. In reality however, dross is more than 75% pure alloy, which just needs processing and refining to render it reusable again. The process of recycling solder dross, removing its inherent impurities and contaminants and making it pure enough for reuse in PCB assembly process is therefore, needed to make electronics manufacturing and assembly more sustainable and eco-friendly.

What are the benefits of recycling it?

The most obvious benefit of recycling solder dross is the reduced strain on the Earth’s natural resources. When manufacturing processes are optimized for maximum consumption of raw materials through dross recycling, the need for further mining of natural ores is reduced drastically, thereby making these operations easier on the planet. Dross recycling offers additional revenue to the manufacturer as the unusable solder waste can be sold off at reasonable process to recycling companies. The process also helps reduce the amount of electronic waste that makes its way into landfills and garbage dumps in the form of solder dross. Overall, it offers a win-win situation for all stakeholders involved in the PCB manufacturing process.

THREE MAIN FUNCTIONS OF LEAD (PB) SOLDER PASTE

Lead solder paste is essentially a well-engineered mixture of a flux, which acts as the medium, and a solder powder. There is not just one kind of solder paste; since it can be engineered, it can be made to display any rheological property by changing the flux and the metals in the solder powder. For different soldering applications, a different consistency of flux is required. Here are three primary functions of lead (Pb) solder paste.

Function #1: Cleaning
Solder paste, with liquid flux as a medium, is semisolid and has another very important function – to clean the area of oxides. Stenciling typically deposits solder paste over the intended areas only, therefore cleaning achieved is also very accurate and effective.

Function #2: Adhesion

Solder paste application on a printed circuit board is also intended to act as an adhesive to hold the components in place until the board is heated to start soldering. Solder paste is capable of keeping the components immobile until a connection is forged.

Function #3: Connection

Solder paste consists of metals that assist in bonding of two surfaces. When heated during soldering, the solder paste melts and achieves a mechanical and electrical connection on the board between the intended components.

Solder paste is an integral part of soldering process and should be executed with care and precision if an effective bond is to be achieved and soldering defects avoided.

A QUICK INTRO GUIDE TO THE PCB ASSEMBLY PROCESS

Manufacture of printed circuit boards is a highly complex process, which does not look very difficult on the surface. However, it actually requires high attention to detail if a good printed circuit board is to be produced. All the surface mount components to be placed on a circuit board need to be assembled and soldered in precision. This blog is designed to provide you with a quick introduction to the PCB assembly process.

Step #1: Solder stencils

In the first step, a stencil is placed over the circuit board. Stencils help in application of solder flux and paste to the areas where soldering is to be done. Stencils are used for precision works.

Step #2: Placing

Back when mechanization of processes was still a thing of the future, placing the surface mount components onto the board after fluxing was done manually. However, today, machines do all the component placement work, and everything is automated. PCB designs are fed into computers which then run the pick and place machines.

Step #3: Reflow

After placing the components onto the board, the job is to keep them at their designated places. This is achieved by passing the board through a reflow oven, wherein the PCB is heated to temperatures higher than 200°C. This melts the metal in the solder paste. Further ahead in the oven there are cooler heaters which work to solidify the molten metal in the paste. This controlled heating and cooling ensures that all the surface mount PCB components are permanently joined with the board.

Step #4: Quality examination

Checking placement and connection errors is a necessary step in the manufacture of PCBs, otherwise all the exercise above would have been for naught if the boards were to come out faulty. The checks can be manual or automated.

Assembly of PCB can be done in many ways. Manual assembly is time consuming. Automated process, if maintained and run well, is always better.

SOLDER: WHAT IS IT AND HOW TO USE IT

Electronics are the stars of this time and age. Daily routine seems impossible to go through without the everyday conveniences that various electronic devices make possible. The electronics industry today is one of the most thriving and happening industries in the world. Thanks to a certain technique that makes it possible to develop devices that can do practically anything, now the populace can sit back and enjoy the fruits of all of it. This technology is soldering. In this blog, you will learn about this revolutionary technique and the soldering materials that have changed the way electronics are perceived in this world.

What is solder?
Solder is typically an alloy used to create an electrically conductive bond between two metals. This alloy makes fusing two metals possible by melting and connecting the two surfaces. In order for this bond to be permanent and efficient, it is necessary for the connection surfaces to be clean and free of oxidation. There are many types of soldering materials available in the market, so that you can choose the one best suited for your needs.

•    Lead solder – This solder is composed of tin and lead, and is one of the most commonly used solders out there.

•    Flux-core solder – this solder is packed with convenience. It has flux material at its core so the users don’t have to apply it prior to soldering.

•    Hard solder – these solders are typically made from copper fused with either zinc or silver. This alloy melts at high temperatures and is used for brazing.

•    Lead-free solder – this solder is an alloy that was developed to be lead-free and environment friendly. These alloys are made up of bismuth, indium, coppers, silver, etc.

How to use solder?
Solders are usually available as coils of solder wire. After you have heated up and cleaned the soldering iron, touch the solder wire to the tip of the iron and tin it – it helps achieve a better soldered joint. One can also find solder spheres in the market. To use solder balls, you need a stencil and flux paste. Alternatively, you can employ BGA JIG that already have embedded solder balls. If any of the above solder use is not suitable for your process, you can also employ fully automated machinery.

MATERIALS AND TOOLS NEEDED FOR SOLDERING

Soldering is one of the most commonly used methods to fix components on a board while assembling an electronic circuit. The process is time-tested and, if used effectively, can create highly reliable, strong, resilient and electrically conductive joints between surfaces. So, if you are currently working on a circuit assembly, you will need a host of materials and tools in order to achieve proper joints between components and surfaces. This blog post provides you with a list of soldering materials and tools that you will need for your circuit board assembly process.

For soldering, you will need:

• Soldering iron for heating the solder wire for making it wettable so that it can be applied to the surfaces to be joined to create a connection between them.

• Solder wire, which is basically a thin strip of appropriate alloy which when heated, becomes the metal filler that connects the two surfaces that are being soldered to each other.

• Flux that will be used to clean the surfaces being soldered as well as the tip of the soldering iron. Its function is to remove impurities, especially oxidation, from the surfaces to ensure the creation of a reliable solder bond.

• Solder balls, in case your circuit assembly involves Ball Grid Array (BGA) packaging.

• Solder paste, in case your circuit assembly requires the use of through-hole soldering for printed circuit boards.

• Tweezers for moving, lifting and placing miniature electronic components that are needed to complete the circuit board with precision.

• Rubbing alcohol or a similar solvent for cleaning circuit board surfaces as well as for removing flux residue after the soldering process is complete.

• De-soldering tools like solder suckers and solder wicks that can help remove excess solder material from the circuit surface. It can also come in handy in case you make a mistake and need to start the soldering process over.

• Wire cutter or shears for cutting solder wires or stripping away the ends of components/wires being joined.

• USB microscope, in case your circuit assembly involves use of fine-pitch components and to discover tiny solder deposits of solder that shouldn’t be there.

• Safety glasses and gloves, for protecting your eyes and skin from the damage that contact with molten solder and solder fumes can cause.

PROS AND CONS OF SOLDER PASTE STENCILS

All electronic devices have a printed circuit board fit into them. It is the most basic component, needed for all electronics to function the way they are meant to. Printed circuit boards are manufactured with high precision, which, today, is made possible through the usage of solder paste stencils. A stencil is a device which is made from a thin foil or filament, which is cut either manually or robotically, in accordance with the design of the printed circuit board. This stencil is especially useful for application of solder paste onto the board, which aids further processes. This blog discusses the pros and cons of solder paste stencils.

Pros
 
•    Stencils are extremely easy to set-up and use. For a mass-manufacturing process, stencils are extremely useful and economical because a single stencil can be reused for multiple solder paste applications.

•    Stencils allow on-contact and off-contact printing on printed circuit boards.

•    Stencils allow usage of a wider range of viscosities of solder pastes.

•    Stencils are extremely easy to clean.

•    Stencils do not plug up easily.

•    Stencils are extremely convenient to use in cases of multilevel printing of circuit boards.

Cons
 
•    Stencils may increase cost of production where the design of circuit boards changes frequently.

•    They require proper maintenance and storage in order for them to keep functioning properly as the material they are made of may bend and disturb the aperture or openings, which may create problems while printing and result in defected products.

Stencils enable a highly efficient production of printed circuit boards. If you own a PCB manufacturing facility, using stencils will be highly profitable for you.

SMT & SMD APPLICATIONS OF SOLDER PASTE

For those who are new to the world of electronic assembly, solder paste is that grey goo-like material that comes in a tub or tube and has the consistency of cake frosting. For those who want to get into the details of this substance, solder paste is power metal solder that is suspended in a thick viscose medium known as flux. This medium does two things – it holds together the components that are being soldered and it scours the surfaces of impurities to ensure that a strong and reliable solder joint is formed between them. Let’s explore solder paste further and understand its application in SMT and SMD processes.

Applications of solder paste

Solder paste is extensively used in industrial scale for SMT and SMD production where accurate application of solder alloy to components needs to be managed efficiently and effectively. It is especially advantageous for miniaturized circuit assemblies that are used in handheld electronic devices like smart phones, tablets, computer motherboards, military electronics, automotive systems, medical equipment and more. It is also used in through-hole, pin-in-paste components where the paste is applied and spread in/over the holes in a printed circuit board with the help of a squeegee. This flux medium, being sticky, holds the components in place while the PCB is heated or baked till the metal components in the solder paste melt and form strong mechanical and electrical joints between intended surfaces.

Composition of solder paste

The composition of solder paste varies based on the properties expected from it for the specific SMT and SMD processes where it will be used. For example, soldering plastic component packages to glass epoxy circuit boards requires the use of solder paste with Sn/Pb or Sn/Ag/Cu compositions. High shear strength requirements are suitable to Sn/Pb combination alloys. The solder melting temperature suitable for a particular PCB assembly process also has an impact on which solder paste will work best for your requirements. Solder paste also differs in accordance with the size of the alloy particles that are suspended in the flux paste. The specific features of your PCB printing process and print quality expected from the paste will determine the metal particle size that will best work for your application. The type of flux medium used in the paste (rosin based, water soluble or no-clean) also categorizes the product, again impacting the way your PCB printing and manufacturing process will work.

Hope this information helps further your understanding of solder paste and its importance in the world of PCB manufacturing.

EVERYTHING YOU NEED TO KNOW ABOUT LEAD-FREE SOLDER

Lead-free solder alloys have been garnering quite a lot of interest in the industry, particularly after the advent of the RoHS and WEEE directives that are focusing on ridding electronics manufacturing industry from the use of lead as a vital raw material. Traditional tin lead soldering techniques have been designed to suit the specific needs of the alloys that are no longer in compliance with RoHS.  Lead-free soldering requires managing a whole new set of variables. Here is everything you need to know for creating reliable and viable solder joints for your circuit board using Lead-free  alloys.

·         Lead-free alloys have a much higher melting point than its traditional tin lead counterparts. This means all your process steps and materials must be tweaked/modified to withstand the high temperature requirements of lead-free soldering.

·         Various flux varieties are incapable of sustaining through the increased temperatures necessary for soldering with lead-free alloys. It can get charred and coat your soldering tip and other circuit board surfaces, making re-tinning virtually impossible.

·         The appearance of your solder joints will also change with the switch-over to lead-free alloys. While the result of tin lead alloys is a shiny and even surfaced, the lead-free versions will appear to be duller and coarser.

·         Higher melting points of lead-free alloys means extended dwell times as the wetting process will take a bit longer to complete. You will therefore, have to tweak your soldering operations accordingly.

·         Another factor to take care of when using lead-free alloys is the possibility of bridging and creation of tin whiskers. You will need a lot of practice at handling the soldering iron to ensure the above issues don’t creep up and disrupt the circuitry of your board.

·         Lead-free alloys are also more prone to oxidation owing to the higher temperature they need for becoming wettable. The flux application and surface cleaning steps in your soldering process will therefore, have to be tweaked accordingly.

Keep the above factors in mind and you won’t face any issues while using lead-free alloys for your soldering needs.

KNOW HOW TO USE ROSIN SOLDERING FLUX PASTE

The quality of the soldering joint produced depend majorly on the minor soldering process details. Activities like cleaning the printed circuit board properly and using the right flux are crucial for efficient soldering. After reading this blog, you will know how to use rosin soldering flux paste.

                

Step #1: Getting the right tools

The size of the actual area available on printed circuit board components for soldering can be very small. In order to accurately apply rosin solder flux paste onto such small areas, you need the right tools. Something with a fine tip, like an ice pick, can do the trick for you.

Step #2: Cleaning things up

An unclean printed circuit board is the root cause of ineffectiveness of flux. To ensure that the rosin flux is able to do its job properly, clean the printed circuit board thoroughly.

Step #3: Applying with care

Use the tools you gathered to apply a generous amount of rosin solder flux paste onto the points to be soldered. Try to avoid wastage of flux by keeping your hands steady as you apply.

Step #4: Heating

You can proceed with the soldering iron over the surfaces you just painted with rosin solder flux paste.

Paying attention to the little details while doing precision work will help greatly in achieving flawless solder joints.