PCB Glue: Key Applications and Types

The basic structure of all electronic components is a printed circuit board (PCB).

Also, if you have closely looked at a PCB board, you might have realized some conformal coatings.

A glue or adhesive is primarily the material that aids in attaching parts to the PCB board.

In our article, we'll discuss the critical applications of PCB glue at length.

Also, we'll pay attention to the various types of adhesives for circuit boards.

Therefore, for a detailed exposition of the use of PCB glue in the electronics industry, read on. 

 

What is PCB Glue?

 

Glue is Necessary for Electronic Assembly

 

It is an adhesive central to attaching electronic components to a PCB board.

There are two common types of PCB glue include the RTV super glue, which essentially does not release an acid during curing.

Also, cyanoacrylate super glue (CA) is helpful in instant gluing applications. 

 

Why Use Glue in PCBs?

 

To Enhance Mechanical Strength

 

PCB glue secures components to the board during transportation and operation, creating a sturdy bond that minimizes the risk of looseness or detachment.

 

To Improve Moisture Resistance

 

Some PCB glues are moisture-resistant, which means they form water-resistant barriers that protect the PCB from corrosion and short-circuiting.

 

A robot holding a glue syringe injection above a PCB

 

To Improve Thermal Conductivity

 

Some PCB glues can also operate like thermal pastes because they help to dissipate heat away from heat-generating components.

They can also evacuate heat away from temperature-sensitive components to lengthen their lifespan.

 

Thermal-paste application on a CPU to interface with the heat sink

 

To Provide Electrical Insulation

 

Glue can double up as a dielectric material, separating electrically conductive components to prevent short-circuiting or ground faults.

 

To Streamline Production

 

Glue eliminates the need for clips, screws, or other types of fasteners during assembly, which simplifies the PCB production process.

It can also eliminate the need to solder some components, making the process cheaper and more efficient.

 

Automated hot melt glue application during PCB production

 

To Increase Vibration Resistance

While not as strong as solder, PCB glue holds and secures components to the PCB, preventing damage relating to vibrations when the board is in use.

PCBs in industrial and automotive applications experience tons of vibrations, but PCB glue keeps everything intact.

To Enhance Performance and Reliability

PCB glue combines benefits like enhancing mechanical strength, providing electrical insulation, improving thermal conductivity, and providing moisture resistance, making the PCB perform better and be more reliable.

 

Waterproofed and shock-proofed electronics on a PCB

 

Typical Applications of PCB Glue

 

A Technician Applying Glue

 

The various critical applications of PCB glue include the following: 

 

Surface Mount Components Bonding

 

Automotive Printed Circuit Boards with Surface Mounted Components

 

When attaching surface mount devices (SMDs), the primary step is placing them on beads of uncured adhesive.

The next significant step is curing the glue via ultraviolet radiation or heating.

You might find others referring to the process as chip bonding. 

The essence of the curing process is to facilitate firm attachment of the SMDs.

Essentially, there are two essential uses of surface mount adhesives. They include:

• Acting as a processing aid
• Helpful in enhancing stress relief to the solder attachments. Ideally, the process is significant in preventing a possible failure of the electrical connections. 

Your favorite glue should have an extended shelf life. Also, it's advisable to ensure that the excess adhesive does not affect the sensitive components. The following are some of the preconditions for effective adhesive solutions with SMDs:

• Also, the glue for circuit boards should have rapid curing properties

• Ideally, it should be non-stringing.
• During coating circuit boards, the adhesive should feature high wet strength.
• Also, the bond should have excellent electrical properties after curing. 
• It should be flexible and of high power.

 

Wire Tacking

 

Electronics Repair

 

The tacking process is straightforward to carry out as long as you have PCB glue.

First, ensure that you have stripped the insulation coating when attaching components.

Next, solder the ends to the component leads. Additionally, you'll be required to bond the wires using adhesive materials to the board substrate.

You can use a wide range of glues during this process. For instance, you can use cyanoacrylates or epoxy glue.

Alternatively, you can use light-curing adhesives or acrylics.

When using the former, combining it with an ideal activator is advisable. It facilitates fast curing times to as little as 30 seconds. 

 

Potting and Encapsulating Electronic Components

 

A Manufacturing Circuit Board

 

During potting, you apply the glue to small spaces on the PCB board.

The rationale of this process is to limit physical and environmental damage.

Additionally, the method improves the insulation capability of the surface. 

When choosing potting glue for PCB, ensure it has good chemical properties.

Also, ensure that it has efficient adhesion to metals and plastics. The most common bonds for PCB that you can use during potting include epoxies, silicons, acryls, and polyurethane. 

 

Conformal Coatings

 

An Adhesive

First, note that conformal coatings are not exclusively due to the adhesive bonding process.

Nonetheless, note that adhesive resins are still pertinent in enabling conformal coating.

Thus, you can use epoxies, silicones, acrylics, and polyurethanes in this process. 

Essentially, the critical significance of a conformal coating is board protection from environmental factors.

They include short circuits and moisture from the surroundings.

The layers will also prevent the corroding of solder joints. Additionally, a board with the coating is safe from service temperature changes. 

 

Types of Glue for Circuit Boards

 

Glue Dripping From a Bottle

 

When choosing suitable glue, you need to consider three main stages. They include the solid phase, the transition stage, and lastly, the liquid-resin stage.

Let's now look at the several kinds of glue for circuit boards. 

 

Ultraviolet Curing Glues

 

Super Glue

 

As the name suggests, these glues are light-curing. Several types include encapsulants, adhesives, and coatings.

Note that bonds are common in electronics since they are compatible with the materials. 

Additionally, these glues are easy to relieve and do not require temperature relief. 

When using these glues, you'll realize that many feature acrylic-based details. Also, they have photograph initiators, which are easy to actuate using bright radiation.

However, you cannot apply a thick coat. Essentially, UV will not penetrate very thick coats of the glue. 

 

Thermally Conductive Glues

 

A Circuit Board with Numerous Components

 

Think of a scenario when you want to secure heat sinks to electronic components.

Ideally, you will require a glue that can effectively provide a heat-directing path in such a case. Such kind of an adhesive is hot glue.

Otherwise, heat can be damaging to the working of electronic components. 

You can mix electrically conductive and insulating powders with the glue during application.

Consequently, the glue will have a higher thickness with high thermal conductivity properties.

Therefore, the sealants are essential in creating thermal conducting bonds. 

There are several hot glue PCB formulas. Nonetheless, you can create one by mixing epoxy with acrylics and silicon. 

 

Conductive PCB Adhesive

 

Super Glue

 

Most of the standard glues are not electrically conductive. Consequently, this creates a problem, especially when attaching surface-mount gadgets and coordinated circuits. 

The two applications will require the use of an electrically conductive adhesive.

Luckily, some particular unique glues will efficiently conduct electricity. They include anisotropic sealants and isotropic kinds. 

The former are capable of forming joints that are conductive in all directions.

On the flip side, isotropic glues will only conduct in a unidirectional mode. 

 

Other Types of Glues

 

Types of Glue Illustration

 

Others include the following: 

 

Polyimides

 

The polyimides can withstand up to 300ºC of heat. Thus, they are common in high-technology hardware applications where high temperatures are inevitable. 

 

Silicone Resins

 

Primarily, silicone resins operate as sealants rather than glues. Hence, they are commonplace in conformal coverings as encapsulants.

One key upside of the resins is their low and high-temperature resilience.

They will be in top state at temperatures between – 60ºC to +200ºC. 

 

Cyanoacrylates

 

They are common in attaching wires to a PCB board or other external components.

Essentially, they are single-part glues that quickly dry on application.

However, it is essential to couple their use with activators for improved drying. 

 

What Is the Best Glue for Electronics?

 

The best glue for electronics is epoxy because the adhesive is highly versatile. But UV-curing acrylics are not bad either.

Most assemblers use this glue to attach surface-mount devices to the board.

Silicone is also suitable for securing electronic components, especially conformal coatings and encapsulating parts because the material has superb sealing characteristics.

You can use cyanoacrylates, as well, to reinforce wire connections.

Therefore, you should consider factors like the component’s exposure to the environment, temperature sensitivity, and weight to determine the best glue for the job.

 

An integrated circuit covered in black epoxy on a PCB

 

Is Hot Glue Safe for Circuit Boards?

 

You can use hot glue on electronics; it won’t short the circuits because it is not electrically conductive.

But the element of safety comes about when you have circuitry or parts that get hot.

This adhesive melts at lower temperatures than epoxy, acrylics, silicone, and cyanoacrylate, meaning it will lose its function when things get hot.

Another thing to consider is hot glue is a thermal insulator. So, it will prevent hot power components from radiating heat, leading to failure.

Therefore, you can use it to secure lightweight components or temporary fixes on PCBs, but it is unsafe.

 

How To Remove PCB Glue

 

• Step 1: Disconnect the PCB or device’s power source to eliminate chances of electric shock, which can damage sensitive components.
• Step 2: Identify the glue type to determine the removal process. Silicone and hot glue adhesives usually require sealant removers, isopropyl alcohol, or methylated spirit plus heating, while acrylic and epoxy adhesives require acetone or isopropyl alcohol.
• Step 3: Use a heat gun or a soldering gun at low-temperature settings to apply heat gently above the glue on the PCB to soften it. If you don’t have a heat gun, a hairdryer will do. Don’t overheat one area because you can damage the PCB or components. And remember to use acetone or isopropyl alcohol solvents to soften heat-sensitive adhesives.

 

Gray-colored epoxy resin on a PCB

 

• Step 4: Remove the softened glue using tweezers, plastic scrapers, or dental picks, then clean the area you’ve removed the glue from using a lint-free cloth or cotton swab soaked in isopropyl alcohol or acetone.
• Step 5: Inspect the board and its components to check for signs of damage or left-over adhesive.
• Step 6: Repeat steps three, four, and five if you notice signs of sticky adhesive.
• Step 7: Once the board is adhesive-free, reassemble the device or rework the glue while ensuring all the components are secure and fully functional.

 

PCB Glue FAQs

 

What Is Non-Conductive Glue for PCBs?

 

Non-conductive PCB glue is an adhesive that does not conduct electricity, a property that eliminates the chances of short-circuiting or accidental grounding.

 

What Is Epoxy Glue for PCBs?

 

Epoxy PCB glues are two-part adhesives that come as separate resins and hardeners.

When mixed, these two form a strong, hardened glue resistant to moisture, heat, and chemicals.

A close-up image of two circuit boards with microchips attached via wire bonding versus a drop of black epoxy resin

 

Is There a Glue That Works Like Solder?

 

Cyanoacrylate glue (super glue) has almost similar joint strength to solder, but anisotropic and isotropic glues are your best bet if you want electrically conductive adhesives.

You can’t get both high joint strength and electrical conductivity in one PCB glue, so none works like solder.

 

Can I Use Glue Instead of Electrical Tape?

 

You can use non-conductive glue in place of electrical tape, but avoid using hot glue; it is unsafe for printed circuit boards.

 

Conclusion

 

In a nutshell, a PCB circuit board is the fundamental structure block for all electronic components.

However, to make it worthwhile, the use of the PCB glues we've just covered is unavoidable.

We've also elaborated on the significance of several kinds of PCB glues in operating a circuit board.

Further, we have analyzed the different types of PCB glues. Nonetheless, reach out to us if you have some clarifications you'd like to make.