LearnESD.com » ESD workstation

Soldering iron-the silent killer?

admin — Thu, 12 Jul 2007 13:27:37 +0000

Soldering iron is basically a hand tool with a heatable tip and used to solder two materials together.
Soldering irons are widely used in Electronic industries that produce Printed Circuit Board assemblies or by anyone who needs to do soldering.

Soldering iron is typically electrically powered and comes as a complete soldering station with a variety of features such as
â€¢ soldering iron temperature can be set and controlled or locked to prevent unintentional changes
â€¢ digital display to indicate the soldering iron tip temperature
and with an iron holder.

Some soldering station requires calibration and some does not require calibration as the latter is self calibrating the temperature of the soldering iron tip.

When it is not managed properly, soldering iron can be a silent killer. ESD sensitive devices are damaged without anyone knowing it.
Ungrounded soldering iron tip could damage the ESD sensitive devices by the harmful leakage current flowing to the tip.

An ESD safe soldering iron station is basically a soldering station that is provided with a housing, an iron handler or a cord that is made of anti static material.
The choice whether to own an ESD safe soldering station is depending on the sensitivity of the device being handled at the work area.

The ESD safe soldering station is generally more expensive and is good to have but what is more important is to get hold of a grounded soldering iron.
A very simple way to confirm the soldering iron tip is grounded is by using a multimeter.
A new soldering iron should have the tip to ground resistance that less than 2 ohm, however this resistance would increase with use and it should be less than 20 ohm.

A more practical device to confirm the connection of the soldering iron tip to ground is by using a soldering iron tester. This soldering iron tester does not only allow the checking of iron tip to ground resistance, it also allows the measurement of the soldering iron tip temperature and iron tip to ground potential.
It is recommended to check these parameters periodically as to ensure the equipment is operating properly.

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Ionizer â€“ What is that?

admin — Tue, 23 Jan 2007 16:11:21 +0000

Ionizers are the heart of static control program in clean room environment.
Many insulative materials such as plastic, Teflon, ceramic and glass are widely used as part of the process materials.
Static charges build on these insulative materials when there is a contact and separation with other materials during the processing activities. Unlike the conductive material, static charges on the surface of the insulative materials cannot be drained away. There just stay there.
Charged insulative material can induce opposite charges on a neighbouring ESD sensitive part, which is placed within its electric field. Damage to the part is done when a person touch it in the presence of the electric field. Some ESD sensitive items, for example, reticles are damaged when present in the electric field.
ESD sensitive parts, for example, semiconductor wafer, that has static charges on its surface would attract particulate from the air and contaminate the wafer.
There are a few ways to remove or neutralize static charges on the insulative material.
Using an antistatic solution that is compatible to the environment (clean room compatible when used in clean room environment) or ionizers are the two common methods currently available to minimize static charges on the insulative materials.
Ionizers provide permanent solution when it comes to combat static charges on the insulative materials.Â Neutralization of static charges occurs when ions produced by the ionizers are attracted to the opposite polarity of static charges on the material surfaces.
There are two common types of ionizers that are widely used. There are corona air ionizer and alpha nuclear ionizer.
Corona air ionizers themselves are divided into three types: AC corona ionizers, Steady state DC corona ionizers and pulsed DC corona ionizers.
Corona air ionizers apply high voltage to the sharp emitter points. The strong electric field would accelerate the free electrons that are present in the atmosphere to the positive emitter points. The fast moving electrons collide with the gas molecules and dislodge the weak bonded electrons from the molecules, giving rise to positive ions, which are then repelled, from the positive emitter points.
At the negative emitter points, the free electrons in the atmosphere are pushed away from the emitter points. These fast moving electrons collide with gas molecules and dislodge electrons from the molecules. These dislodged electrons are in the atmosphere for not long before they are captured by other neutral gas molecules and give rise to a flood of negative ions.
Corona air ionizers are not suitable for all applications. Depending on the type of emitter point material used, the ionizers tend to introduce particulate contaminants to the air. The ions balance for corona ionizers would never be zero.
For that reasons, alpha ionizers are the answer. Alpha ionizers are normally used in a volatile environment and in an environment where very sensitive ESD sensitive items are handled which require balanced ionizers.
Alpha ionizers use Polonium 210 radioactive source, which emit alpha particles.
The alpha particle collides with a gas molecule and dislodges an electron. The free electron is then captured by neighbouring neutral gas molecule and becomes a negative ion. A balance number of positive and negative ions are produced in the alpha nuclear ionization process.
There is a local government regulatory rules that need to be followed when alpha ionizers are used. Periodic annual renewal of the alpha nuclear source is also required to ensure proper functionality of the ionizers.
A Charge Plate Monitor (CPM) is commonly used to check the effectiveness of an ionizer.
Monitoring the balance ions (offset voltage) and discharge decay time would be able to tell whether the ionizer performs its intended function.
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Setting up An ESD Protected Workstation

admin — Wed, 10 Jan 2007 13:16:11 +0000

An ESD Protected workstation normally consists of an ESD mat, a wrist strap outlet or wrist strap continuous monitoring system, an ESD flooring or mat with or without an ESD ionizer.

The entire ESD mat, wrist strap outlet or wrist strap continuous monitoring system and the ESD flooring or mat is connected to the same common point to ensure an equipotential bonding.

The common point ground is then connected either to an AC equipment ground or an auxiliary ground.

The auxiliary ground is a separate supplemental grounding conductor for use other than the general AC equipment grounding.

This auxiliary supplemental grounding is bonded to the AC equipment grounding to ensure there is no potential difference between these grounding systems.

An ESD ionizer may or may not be used on the workstation. When there is an essential process insulator on the work surface (e.g. plastic connector container), an ESD ionizer is required to neutralize any static charges that are present on the container.

Other materials and equipments that may be used at the ESD protected workstation are tweezers, soldering irons, torque screwdrivers and chairs.

Soldering irons and torque screwdrivers are AC powered equipments. It is best to ensure the tip of these equipments grounded to prevent any charge transfer while in use.

Tweezers are grounded through the human touch. It is recommended to use the ESD chair at the workstation though not mandatory.

Any decision made on the choice of material and equipment that are used at the ESD workstation must take into account the ESD sensitivity level of the ESD sensitive parts being handled in that area.

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ESD Equipotential Bonding – When to use it? In any electronic ESD sensitive (ESDS) devices or assemblies manufacturing...

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