Publications

You have completed your search for an ideal conformal coating chemistry, one that will provide your PCBs the protection and reliability demanded by your industry and customers. After all that work, you probably assume your job is finished.

The PCB industry continues to evolve with ever increasing demands for efficiency and manufacturing cost reductions. From the design phase onward, suppliers and contract manufacturers are being asked by their OEM overlords for increased performance at lower and lower costs.

This blog post is the second installment in our two-part series on viscosity (with special consideration on adhesives and coatings). In our previous blog post, we discussed the properties of viscosity and how viscosity can be affected by temperature, the addition of dilution or thinning agents, and other similar factors.

The problem is not limited only to rosin fluxes and solvent cleaning, but also occurs when water soluble fluxes are used and when either flux type is removed with water. The soldering and cleaning processes involve so many chemicals in the flux, circuit board, components and cleaning agents that a complete understanding of the reactions is very difficult if not impossible. There are white residue problems with water soluble fluxes and many of the causes not related to the flux compositions are the same as for rosin fluxes.

In the days before surface mount printed circuit assemblies, components (such as resistors, diodes, and capacitors) were axial, and printed circuit board components were installed with the “through-hole” method using large conductor spacing. With the advent of integrated circuits, these too were through-hole with good spacing between legs.

Conformal coatings offer tremendous protection to printed circuit board assemblies, but this assumes they properly adhere to the PCB. Application errors are all too common, causing delamination and otherwise poor adhesion of the material. So before producing at scale, you should routinely conduct adhesion tests to validate the integrity of your production processes

Our popular, newly revised conformal coatings Facts & Data booklet, is designed to form a readily understandable, introductory guide focusing on the main issues of selecting a coating material and putting it into process. Its objective is to present the salient facts in a succinct style rather than attempting to take the reader into a long and detailed scientific explanation (numerous further reading references can be supplied for this purpose).

Conformal coating technology is on a continuous path of improvement, and we're excited to say the latest step on that path just happened. UV550 is the most recent innovation from HumiSeal, continuing the trend of industry-defining capabilities in the conformal coating space. This is to be expected from the original inventors of conformal coating material. But what sets UV550 apart from the rest?

Progressive cavity pumps are ideal solutions for applications requiring a high level of dosing accuracy while minimizing shear on dispensed materials. By nature, progressive cavity pumps operate in accordance with a positive displacement principle. Material flows through the valve as it progresses through fixed cavities created as a helical rotor turns.

HumiSeal chemists have been designing state-of-the-art conformal coatings for nearly 70 years, first producing UV curable coatings more than two decades ago. At that time, UV curable technology was considered the next generation of coatings.

The essential quality features required for these future applications are provided by the multivacuum soldering process. In the multivacuum soldering process assemblies are subjected to several vacuum applications during the soldering process, with the option of applying vacuum processes both before and during the melting of the solder paste.

Tin-Silver-Copper alloys are the primary choice for lead-free SMT assembly. Although there are other options available such as alloys containing bismuth or indium and other elements, tin-silver-copper solders, also known as SAC alloys are by far the most popular. They are used by approximately 65% of users, as last surveyed by Soldertec in 2003.

PCBs have become ubiquitous, not just in automobiles but across products and industries where such things were unimaginable in the past. Consumers have shown a preference, and a willingness to pay, for “smart” technology in products, including outdoor grills, washers and dryers, handheld devices and tools, toasters, and even clothing.

Manual brushing is just one of many methods commonly used for applying conformal coating materials to PCBs and other components. It is a hand-applied method that requires little investment into automation or equipment.

Driven by environmental and health concerns, the RoHS legislation has mandated the electronic assembly industry to transition from eutectic tin-lead to lead-free soldering, which carries forward a revolution in the formulation of soldering materials.

As lead-free gains momentum, many engineers are striving to set-up a wave solder process that maintains production yields but also offer reliable assemblies. Much has been written on these topics in the past 5 years. Less confusion does exist today about alloy choices available to replace leaded solders, however many are struggling with their successful implementation. Once the lead-free alloy is selected, a solid understanding of its chemical and physical properties is required to enable reliable soldering.

A basic definition of a conformal coating is a coating, which is applied to the PCB surface and “conforms” to the various irregularities and contours of components at an even and consistent thickness. This of course means that, as an example, applying 50 microns of dry coating would be measured at 50 microns on flat sections, vertical sections, and corners of components.

Conformal coating thickness is one of the most important characteristics to ensure long-term reliability of your electronics. A minimum coating thickness is essential to provide the required function of the conformal coating, but if a conformal coating application is too thick, it can actually have negative effects on your level of protection.

UV curable conformal coatings have attained widespread use in applications requiring fast through-put times, such as automotive, white goods, and industrial control manufacturing. In addition to speed of cure, UV curable conformal coatings provide the advantage of high physical protection and chemical resistance for electronic systems.

Those of you familiar with engineering or scientific education are probably quite aware of the absolutely critical issue of using the proper units. For those of other backgrounds, the term “units” is just a word for the little words that come after the numbers. When we ask how much you weigh, we expect more than just a number answer; we expect a number and a word denoting the unit of measure or units.

The oven recipe, which consists of the reflow oven zone temperature settings and the speed of the conveyor, will determine a specific time‐temperature profile for a given PCB assembly. In order to achieve a good quality PCB assembly, the time‐temperature profile should be within the product and process specifications.

Electrochemical migration (ECM) is an electrochemical process where metal ions move between adjacent metal conductors through an electrolyte solution subjected to an applied electric field. ECM is also characterized by the dendrites growth on printed circuit boards (PCBs).

Surface chemistry is an enormously complex and cussed branch of the sciences; consequently, we will attempt only a layman's discussion and understanding here. For the purposes of conformal coating, surface energy must be considered for both the exposed surface of the PCB as well as for the coating itself.

The majority of today’s SMT market today in the United States and Europe is high-mix/low- to medium-volume and parts of it even are considered extreme high-mix and/or extreme low-volume.

The general rules listed below can be applied to nearly all of the conformal coating processes. They are advice only. They have to be interpreted carefully and adapted to the circuit board. Ultimately, they may save you time, money and a lot of heartache in the conformal coating process.

This paper will discuss commonly experienced defects associated with NoClean surface mount processes and propose methods to solve these issues. Much of the discussion can be applied to any surface mount process (i.e. water soluble, RMA, or No-Clean), but some are directly associated with No-Clean processes.

To an equipment manufacturer, conformal coating materials are the essential piece to a customer’s success or failure. The marriage of material and correct application equipment dictates everything from process implementation, line efficiency, quality, and customer satisfaction. This interdependency drives chemical companies and equipment suppliers to a unique relationship.

Pockets of gas, or voids, trapped in the solder interface between discrete power management devices and circuit assemblies are, unfortunately, excellent insulators, or barriers to thermal conductivity. This resistance to heat flow reduces the electrical efficiency of these devices, reducing battery life and expected functional lifetime of electronic assemblies.

This paper will discuss the results of a thorough comparison of the various methods of attaching thermocouples to a printed circuit board for thermal profiling. The focus will be on non-destructive attachment methods and how well they compare to the standard method of attachment using high temperature solder.

This is the first in a short series on material viscosity, in which we will review what it is and how to measure it. We will start with the definition of viscosity. Viscosity is the internal friction of moving fluid and a measurement of the resistance of a fluid deformed by shear stress. It is measured in centiPoise. The lower the number, the less viscous the material, as can be seen by this comparison chart: starting with water at 1 cPs and ending with honey at anywhere between 2,000 – 10,000 cPs.

With solder reflow, relying on commonly accepted practices can lead engineers to overlook some relatively simple factors that are critical to optimizing the process. An examination of six “conventional wisdom” tenets reveals that challenging them can contribute significantly to improved yields.

As powerful electronics shrink in size and increase in variety, thermal interface materials [TIM] for heat dissipation continue to gain importance in the manufacturing industry. A variety of methods exist for aiding this heat transfer. Gap filling pads, adhesive tapes, and dispensable gels are the most common. The primary considerations when selecting a TIM material is the thermal conductivity and dielectric strength.

The transition to LED curable conformal coatings is beginning to build momentum, beginning as a slow evolution and developing into a revolution of sorts. If you and your organization are faced with aging equipment and higher costs, there isn't a better time to consider the potential advantages of LED curable conformal coatings!

Manufactures who have looked at VOC-Free fluxes have discovered that VOC-free fluxes are not simply "drop in" replacements for the existing flux chemistries. Because VOC-free fluxes contain water as a solvent difficulties are encountered when soldering boards with these fluxes. The difference between VOC-Free and alcohol based fluxes lies in the characteristics of the solvent (thinner).

Conformal coating is generally the last step in the PCB manufacturing process and the method of protection for all those valuable functional components, but it's not always that simple. Let's look at a fairly common scenario.

The past few years have seen the introduction of a number of thinner-film circuit board protection products of various chemistries, many of which have been generically termed “nano-coatings” by manufacturers despite confusion regarding what this really means.

In the world of bonding, filling, and encapsulating the term “meter-mix” refers to the process and the hardware required to accurately manage, blend, and dispense multi-part fluids in an automated fashion. Most often in electronics and industrial dispensing, meter-mix dispensing is based upon processing a 2-part adhesive that is supplied as a base component plus a hardener component.

Conformal coatings have a long and storied history with printed circuit boards. A good conformal coating protects PCB components from moisture, corrosion, contaminants, and additional PCB threats like vibration and thermal shock. Coatings are a complicated science, and there isn’t one best coating or application method for every job.

It is critical to minimize mechanical fasteners and protective housings in EV motors due to weight considerations and the speed of assembly factors. Polymeric protectants and adhesives are ideal in these circumstances. There are a number of common applications for high-performance adhesives and coatings within EV motor assemblies.

During the assembly process, the use of a liquid optically clear adhesive (LOCA) is important for ideal visual properties in LCD screen manufacture. The assembly process has evolved and advanced, but there are still potential weaknesses or defects that must be taken into account in both adhesive selection and process design. In this blog installment, we will discuss one of these potential defects: entrapped bubbles.

Haze and lack of clarity are considered among the most vexing and stubborn of defects in the assembly of LCD screens and surfaces. Significant advances have been made in the optical quality and capability of liquid crystals and LEDs; however, these advances can be stunted by choices made further along in the assembly process.

For decades, Chase Corporation and our Humiseal brand have been the originators and recognized leaders in PCB protection with conformal coatings. Humiseal also provides products and technical support for a complete line of encapsulants. While conformal coatings provide adequate protection in most instances, sometimes you just need a little more coverage!

Voids in solder joints are largely a function of differential pressure between vapor pressure of the gases inside of the joint and environmental conditions. By entering joints still in their liquid state into decompression chambers, voids can be eliminated.

Due to the switch to lead-free manufacturers are faced with multiple new challenges. Simple processing, successful soldering for various products, high quality and user-friendliness are the basic requirements that current soldering systems have to provide. Vapor phase soldering meets these demands. However, individual systems vary greatly when looking at important details

The modern production of electronic assemblies in SMD-technology is unthinkable without the efficient printing process, placement process and particularly the soldering technology. In particular, for a high and constant product quality the soldering technology is of utmost importance. From the start of the SMD-technology there have been two processes competing constantly with each other.

Vapor Phase Soldering is also known as Condensation Soldering. In the first process step the cold PCB is delivered to a chamber in which there is vapor evaporated from a special liquid (medium) for this process perfluoropolyether (PFPE). The liquid is chemically inert and with density almost twice higher than the water.

Back in 1999 ASSCON’s invention of the worldwide first vapour phase vacuum soldering process has already set a milestone for industrial electronic production. The vacuum soldering process proofed as a successful solution for constantly challenging soldering tasks while process windows were getting continuously smaller. The rising number of vapour phase vacuum soldering systems in the electronic industry proofs the essential impact of this vacuum soldering process.

Vapor phase reflow soldering systems set standards in the soldering technology. Vapor as energy transfer medium is one of the most efficient procedures for the heating of assemblies. The efficiency is much higher than with the heating of convection. Through the use of a special liquid GALDEN, an oxygen-free atmosphere is created, where the whole pre-heating and soldering process is running oxidation-free.

Vapor phase soldering is the ideal process for modern soldering technology. Electronic assemblies can be soldered faultlessly in each configuration. Easy and flexible adjustable temperature gradients assure for each product the optimal, absolutely reproducible temperature profile. No complex test series and line set-up times – applicable from prototype up to serial production.

Moisture can accelerate various failure mechanisms in printed circuit board assemblies. Moisture can be initially present in the epoxy glass prepreg, absorbed during the wet processes in printed circuit board manufacturing, or diffuse into the printed circuit board during storage. Moisture can reside in the resin, resin/glass interfaces, and micro-cracks or voids due to defects.

The cost of selective conformal coating equipment can easily run into hundreds of thousands of dollars. Even those who invest in the latest selective coating technology find, at times, that masking in certain areas is the only solution. The need for masking often becomes more pronounced in smaller-volume, variable product-mix manufacturing.