Preventing ESD Damage in SMT | 7 Benefits of Dry Fog Humidification (Part 1)

 

7 benefits of Dry Fog Humidification in SMT processes

In surface-mount technology (SMT) processes, humidity control is essential to prevent electrostatic discharge (ESD) damage and problems with static electricity or dry air. Among all the methods to control humidity, the Dry Fog* Humidification system from IKEUCHI is the only one able to achieve all seven of these benefits.

*A fog formed out of ultrafine water droplets, each measuring 10 μm or less in diameter, which are created by specialized spray nozzles, to instantly evaporate into the air or bounce off any object instead of bursting on impact.

1. Preventing ESD damage
2. Reducing pick-and-place errors
3. Maintaining consistent solder print quality
4. Reducing airborne particles
5. Significant reduction in operating costs
6. Reducing cooling costs
7. Less sick leave

In this article ESD damage and pick-and-place errors will be discussed, as mentioned in the table of contents under 1 and 2.

1. Preventing ESD damage

When a human body charged with static electricity comes into contact with a conductor, static electricity is discharged and an electric current flows. It only takes a fraction of the possible electricity a human body can discharge to destroy the circuitry or damage the inside of these sensitive components. This is called electrostatic discharge damage or ESD damage.

 

In recent years, as electronic devices have become smaller and smaller and are equipped with more advanced features, their electronic components are also becoming smaller and smaller. The size of chip resistors and multilayer ceramic chip capacitors mounted on smartphone circuit boards is mainly 0402 (0.4 x 0.2 mm), but with the introduction of the 0201 (0.25 x 0.125 mm) size in 2019, further miniaturization is expected.

However, as the size of the components decreases, the withstand voltage of the components is also reduced, making them more susceptible to damage. This requires that SMT processes which handle these components, including ICs, take more active precautions.

 

A first and basic measure is wearing a grounding wrist strap and connecting it to the proper grounding equipment, this will release any electrostatic immediately and protect the components from ESD damage.

 

In addition, an ionizer (static eliminator) can be used to remove the static charge built up on products or equipment. However, the ionizer is not a perfect solution to prevent ESD damage, since it needs to be installed wherever static electricity is generated, requiring sufficient space for installation.

 

It is the prevention of static electricity through air humidification that complements the measures taken with ionizers.

IKEUCHI’s industrial “Dry Fog Humidification System” raises the humidity to an appropriate level creating a way for the electrostatic to dissipate making the entire work environment, not just certain areas, less susceptible to electrostatic charge.

 

Since humidification with Dry Fog helps moisture to directly dissolve into the air, it effectively increases humidity without wetting products, machines, or floors, and prevents static electricity itself from being generated. The system is equipped with a humidity controller that enables automated operation to maintain a uniform humidity level even in large spaces.

 

The graph below shows the number of in-process defects and humidity levels for each month in a one year period at an IC memory manufacturer prior to installing our humidification system. It indicates that most of the defects occurred during the dry season from November to March.

The installation of the humidification system successfully prevented static electricity from being generated due to low humidity in wintertime and greatly reduced the number of the defects caused by the elecrostatic discharge (ESD).

 

2. Reducing pick-and-place errors

Electronic components for SMT processes are typically supplied on packaging tape rolled into reels which are set in the feeder section of the mounting machine. The packaging tape consists of a carrier tape with pockets to carry the components to the mounter head, and a cover tape that seals the components into the pockets.

 

Surface mounting is a process in which multiple nozzles located on the mounting machine pick up the components out of the carrier tape pockets and place them in their predetermined positions on a printed circuit board.

 

During this process, the feeder peels off the cover tape to expose the components as the carrier tape moves forward and the head with the nozzle moves into position to pick up the components. However, the static electricity generated by the removal of the cover tape can cause components to stick to the tape or pop out of the pocket, resulting in a pickup error due to the missing component.

While unmounted components will be detected in a following inspection, it causes additional work and inspections, which means that a pick-and-place error directly affects productivity.

The graph below shows the relation between the number of pick-and-place errors and the humidity in a surface mount facility, recorded every day for a month. The scale on the left shows the relative humidity level and it clearly indicates that on the days the humidity falls below 40% there is a drastically higher rate of pick-and-place errors. In other words, with appropriate humidity control productivity can be increased by preventing ESD damage and pick-and-place errors.

 

Summary | 7 benefits of Dry Fog Humidification in SMT processes

Controlling humidity in SMT processes provides seven benefits. Among all the methods to control humidity, the Dry Fog Humidification system from IKEUCHI is the only one able to achieve all of these benefits.

1. Preventing ESD damage
2. Reducing pick-and-place errors
3. Maintaining consistent solder print quality
4. Reducing airborne particles
5. Significant reduction in operating costs
6. Reducing cooling costs
7. Less sick leave

Look out for future articles and a discussion of the rest of the benefits.The next article will deal with benefits 3 and 4 from the above list.