PCB Manipulation - ESD Safe

Catherine_Bernier 2016-07-08

Electrostatic Discharge is an important problem when working with electronic components just like PCB. Manipulating those devices can be a challenge when we look at automation since there is a lot of electronic components around.

Manipulating PCB with our grippers
Our grippers are grounded through the robot ground and the fingertips are isolated from the rest of the gripper. So if your workstation, boards and robot (which it is initially) is uncharged, there shouldn't be any problem for manipulating PCB.

ESD Control Standards

However, it is possible for you to respect the ESD control standards by modifying or manufacturing the fingertips.

We have the CAD models and measurements to be able to design your own fingertip s. According to the standard, you would simply need to ground the fingertip through the specified resistance (typically 1 megaOhm) using an external cable.

From the EOS/ESD Association website, you can find more info on how to avoid any risk related to ESD.

Here are the six basic principles of static control:

Design in protection
Define the level of control needed in your environment
Identify and define the electrostatic protected areas (EPA)
Reduce electrostatic charge generation
Dissipate and neutralize
Protect products

Anyone using our gripper to manipulate PCB?
Feel free to share your experiences.

Samuel_Bouchard 2016-08-23

@Ryan_Weaver you guys have had such an application in the past, right? How did you manage to use the gripper in an ESD sensitive application?

Catherine_Bernier 2016-08-31

@Grady_Turner Anything on your side to make the gripper ESD Safe?

Grady_Turner 2016-08-31

@Catherine_Bernier @Samuel_Bouchard We have not run into any ESD applications as yet. Sorry I can't offer any information

Etienne_Samson 2016-08-31

@Catherine_Bernier @Samuel_Bouchard @Grady_Turner I have seen some of our customer doing ESD applications, they had to modify the Grippers, since our finger are floating, we are not ESD safe, the only thing you need to do is to attach a conducting wire that runs from the fingertip to the ground. Then we would be ESD safe (if you fingertip are conductive).

Below is a picture from the instruction manual that will help you out, you can see that the Gripper casing is linked to the GND, but not the fingers:

kilnicki 2016-09-16

I was wondering if Universal Robots are somehow protected to work in ESD sensitive application?
As I understand, the gripper have to be grounded to ensure no Electrostatic Discharges, but what about the robot arm itself?

Catherine_Bernier 2016-09-26

That's a good question @kilnicki. Let's see what UR thinks of it, @Stefan_Stubgaard.

Thanks.

Stefan_Stubgaard 2016-09-27

Yes, UR robots can work in ESD sensitive applications.

Robot arm is grounded through the cable from controlbox, controlbox needs to have a proper ground connection, this is good practice for all applications.

UR3, UR5 and UR10 CB3 robots have recently been cleanroom certified by TüV and conforms with ISO 14644-1: http://www.universal-robots.com/about-universal-robots/news-centre/universal-robots-now-certified-for-applications-in-cleanroom-environments/ which will allow them to operate in electronics industry

Robot arms are cleanroom class 5 and controlbox is cleanroom class 6

matthewd92 2016-09-27

@Stefan_Stubgaard that is good news regarding the clean room and ESD. Thank you for sharing that with us

carrondo 2016-09-30

@Stefan_Stubgaard any plan to update also the plastic covers?

balpetter 2016-10-02

@carrondo
I've recently been on UR training and this topic emerged there as well.

We've got a promise that the plastic covers will be upgraded with ESD safe material in a few months as of more customers had this request towards UR.

Stefan_Stubgaard 2016-10-03

@carrondo and @matthewd92 I can give you no fixed timeline, but can confirm that Universal Robots are currently working on ESD-safe lids (it shouldn't stop you from purchasing UR robots of course :) , as the lids (if required) easily can be replaced later in the process)

carrondo 2016-10-03

@matthewd92 and @Stefan_Stubgaard thanks for your additions. Ourselves we're requesting this for quite some time and waiting for news.

elt 2016-10-06

There are actually two common requirements for ESD-safe operation:

Don't build up static charges
Safely dissipate charge that may have built up.

Grounding the gripper fingers and using conductive or dissipative material for the fingertips can indeed prevent charge from building up. This will prevent charge that may be generated by the robot and gripper system (friction between cables and hoses, for example) or that is transferred from outside (like from an ungrounded human) from building up on the gripper and later being transferred to the workpiece.

The larger issue is what happens when the workpiece already has some charge on it. Suddenly discharging this to ground is equally damaging as transferring charge the other way. Workpiece charge can be created by ungrounded humans, poor packaging, and even waving the part around in dry air. When a well-grounded gripper then touches the workpiece, the sparks fly. Many electronics manufacturers therefore require that there be a controlled resistive path to ground (generally around 1-10 MΩ) for anything that touches the workpiece.

If you can guarantee that only dissipative material (like dissipative synthetic finger tips) touch the workpiece, and that this dissipative material has a hard path to earth ground on the other side, that can fulfill the requirements. If you must use metal finger tips, you may have to insulate them from the gripper, and connect the fingertips to an earth ground through a resistor.

Some manufacturers can get quite exacting about having absolutely no pieces of insulative material anywhere near their parts. Hence the requests for dissipative plastic caps on the robot. That may seem like overkill, but some applications specify a maximum static voltage of 50V or even 10V. Just scuffling your feet can generate thousands of volts.

Just as with risk assessments, ESD protection is a negotiation guided by standards, the application, and common sense.