There are many different soldering stations used on electronic assemblies today, and due to the evolution of electronics over the last decade, the sensitivity of the components on the PCB to Electrical Over-Stress or Electro Static Discharge (EOS/ESD) had risen greatly.
To adequately protect the PCB, it is important to control the points where the PCB can be subjected to EOS/ESD. Those points include but may not be limited to:
- Grounding of the operator
- Grounding of the working surface and tools being used
- Removal of all static charge producing materials in the immediate vicinity to the PCB
- Use of ionization or other charge mitigating techniques to neutralize a charge if dissipation through grounding is not possible.
- Storage, transportation, and handling of the PCB using appropriate protective packaging or carriers that will protect the PCB from stray charges and will not themselves induce a charge.
All HAKKO products that bare the ESD SAFE label and symbol have had their product design tested and validated by an independent third-party testing laboratory and an iNARTE certified engineer following the ANSI/ESD S20.20-2007 standard and the ESD STM13.1-2000 Standard Test Method.
In all testing, the product design passes every requirement.
One key factor for any ESD safe product is that the product be properly grounded. As noted in the points outlined above, grounding of the operator is very important and so too is the grounding of the tools being used. You should not consider one without the other.
It is always best practice as part of any ESD control system, to routinely validate the operating conditions and EOS/ESD control measures that are in place, which includes period validation that the facility ESD and equipment grounds have equal potential and are properly functioning. The ANSI/ESD S20.20-2007 does state that this period verification is not necessary if continuous monitoring is being performed.
Some soldering station manufacturers claim that their soldering stations can ‘guarantee’ the grounding of the soldering iron tip and therefore you will not need to follow the best practices of an ESD control system and validate grounding of the operator and soldering station.
This statement is simply false because there is no way by which the necessary grounding can be guaranteed to be effective to the point where the soldering iron will come in contact with the PCB that contains the sensitive components.
Take for example an operator that enters the facility and checks to ensure their writs strap ground is working properly. The test that is done at the door when entering the facility says that the grounding of the operator is okay at that point, but what happens when the operator sits at their workstation?
Some companies make use of active workstation ESD grounding monitors, but this requires that a current must be passed through the system so that the resistance of the system can be evaluated to determine if the grounding of the operator is effective. In some cases, this can mean a voltage of approximately 2.5V to as high as 6.4V may be applied directly to the operator while they are in contact with a PCB that can have sensitive components! Furthermore, the resistance at any mechanical connection point may change due to the buildup of debris or residues that increase the surface resistance of the contact and thereby increase the resistance of the connection to the ground monitoring system.
The same is true for soldering stations. Because the tip is made of metal and is highly conductive, it is necessary to ensure that the tip is grounded. The only active method to ensure the tip is grounded is to pass a current through the tip to ensure the resistance of the tip to the station ground is less than 2 ohms. But the problem with this type of system is that it will generally require a voltage applied to the tip that is in excess of the 2mV RMS voltage that is permitted to be on the soldering iron tip when in use.
Imagine the effects on your PCB if the soldering iron tip has 5V leaking off the tip! Say bye-bye to the sensitive components on that board!
So exactly how do these so called ‘guaranteed’ systems work? They only check the ground at the station itself and there is NO active monitoring of the actual tip-to-ground resistance which is required per the ANSI/ESD S20.20-2007 specification to be under 2 ohms, and therefore since there is no continuous monitoring, then period validation of tip-to-ground is still required.
The mechanical connection of the soldering iron tip to the handpiece, and the handpiece to the station are both points where resistance can build and thereby increase the tip-to-ground resistance to a level outside the acceptable range according to any reasonable ESD control program, yet the ground check of the station will not detect any issue.
Take for example the following tip:
This soldering iron tip is from one of those so called ‘guaranteed’ systems, and even though the tip-to-ground resistance in this example is infinite, there is NO indication of any problem with grounding by the soldering station.
As the saying goes, “Trust, but verify!” No soldering station can guarantee the grounding of the tip or eliminate the ESD requirement to periodically validate the system.
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