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SMD Adhesives Gluing Process

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#59827

SMD Adhesives Gluing Process | 10 September, 2009

In the SMT “Gluing Process” we are using “Thermosetting Polymer-SMT-Adhesive” which surface resistance is 1.5*10E12 Ohm. As per ESDS:2020 we should not allow any material near the component which resistance is >1*10E9~11. Pl confirm me about the ESD requirement of this process. How i will ensure that process is ESD safe?

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#59828

SMD Adhesives Gluing Process | 10 September, 2009

The adhesive should be a dielectric (insulator) by design, if not it could possibly short across leads of the very parts it's intended to secure. It normally isn't a concern - what is the surface resistance of your soldermask, bodies of ICs, ...etc.

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#59830

SMD Adhesives Gluing Process | 10 September, 2009

Questions are: * Could it be that there's a difference between Surface Resistivity and Volume Resistivity? * Where in S20.20 2007 [ http://www.esdproduct.com/ESD_standard%20_S20.20-2007FINAL_000.pdf ] do you find the number [>1*10E9~11] that you reference? What are the units of this number?

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#59885

SMD Adhesives Gluing Process | 18 September, 2009

Hi Davef & Mikes, Thanks for the response. I am agree with both of your point. If the component bosy will be fall in Coductive or dissipative range, there are chances of shorting. Other thing in ESDS:2020 8.3 para is saying to keep away all the insulating items. "Separate the insulator from the ESD-sensitive device by a distance of 30 cm (12 inches)".

In our company we have to follow the ESDS:2020 guideline and also produce the work according to process. If during the Glue processs charge will generate, then how it will be discharge, because there is no grounding path from the surface. The same thing i am facing here in conformal coating process also. Confirmal coating is a insulating liquid which we are applying on the whole mounted PCB. How we are protecting the component from charge. I am very new in ESD field. That's why confused. Hope you are understanding my queries.

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#59922

SMD Adhesives Gluing Process | 21 September, 2009

First, we're not real concerned about gluing induced ESD damage, but conformal coating has a tremendous potential to damage sensitive components. We found a charge of 12 kV generated during the aerosol spraying.

Second, ESD-stuff IS very confusing. Largely because people don't know what they're talking about. The BEST source of information on setting-up a cost-effective ESD program is: "ESD Program Management: A Realistic Approach to Continuous Measurable Improvement in Static Control," G. Theodore Dangelmayer, Van Nostrand Reinhold, 1990 2e [0442237944]. You can find it used through online booksellers for $10-15.

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#59929

SMD Adhesives Gluing Process | 22 September, 2009

Thnaks for the input.

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#59934

SMD Adhesives Gluing Process | 22 September, 2009

> Second, ESD-stuff > IS very confusing. Largely because people don't > know what they're talking about.

I think a lot of that is because of followers following followers.

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#59947

SMD Adhesives Gluing Process | 22 September, 2009

Hi Stephen,

Can you pl suggest what exactly needed for the process? There is no any standard method to ensure for the ESD damage. ESDS:2020 is talking about only for persoanl and equipement grounding mechanism, in the process no insulator should be within 12" as per ESDS:2020.

What we need to do as a process and Quality ESD Engineer?

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#59955

SMD Adhesives Gluing Process | 23 September, 2009

I did see ESD issues years ago when we tried using a plastic stencil to print SMT glue. We measured a huge charge on boards indexed out of the printer. I tried ionizing fans but that didn't help. We now only use metal stencils for printing adhesives.

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#59964

SMD Adhesives Gluing Process | 24 September, 2009

Can you pl let us know what was the ESD sensitivity level of your assembly? We are also using plastic stencil from last 3 years and not seeing any major diffficulties in our class-3 product.

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#59968

SMD Adhesives Gluing Process | 24 September, 2009

We're in the high reliability market and build to IPC Class 3 standards. I honestly don't know much about ESD but our in-house expert measured an 8kV charge on the board after printing with a plastic stencil and rubber squeegees. He wasn't too pleased. We've been printing glue in production for 11 years now using metal stencils and it's been a flawless process.

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