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Date: Thu, 6 Jun 1996 16:29:25 -0400
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To: "Greg Bartlett" <[log in to unmask]>
Subject: Re: ASSY- Laser Ash?
From: [log in to unmask] (Marshall Andrews)
Cc: "technet" <[log in to unmask]>
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Hi Marshall :
I have not heard of any process that coats the surface before laser
marking. All (if not most) IC manufacturers do direct laser marking on the
package. The objective of using laser for marking is to simply the process
not add additional steps. The contrast on the surface is usually acheieved
with the mold compound composition and the texture of the surface (the
smoother the better)
Laser marking is the use of the laser energy (heat) to convert some portion
of the plastic mold compound to another form that forms the print. The
laser also etches off about 1-3 mils (or deeper) into the package surface.
This is like having a tatoo done.
To Norm Dill :
I would suggest that the problem you are seeing is probably not from the
laser marking. If this is the case, you would see a degradation of the
marking constrast after the wash.
You might want to check the wash that you use for possible residue
formation with your flux residues, etc or the purity of your water. If the
problem persist, you might want to sent samples of your residue for
chemical analysis.
regards
Jeff-MH Tan
Hewlett-Packard Singapore
IC Business Division
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______________________________ Reply Separator _________________________________
Subject: Re: ASSY- Laser Ash?
Author: Non-HP-yoda ([log in to unmask]) at HP-Singapore,shargw19
Date: 6/7/96 4:29 AM
Greg, typically the laser does not scribe directly into the plastic of the
package body because it does not create enough contrast. The surface of the
package is usually coated with a thin film and it is this material that is
scribed by the laser. Unfortunately, I do not know the chemical composition
of these coating materials, but I suspect that this is what you are having
trouble adhering to.
Regards,
Marshall
On Jun 06, 1996 13:22:40, '"Greg Bartlett" <[log in to unmask]>' wrote:
>RE>ASSY: Laser Ash? 6/6/96
>
>Funny that you should mention this, Norm. I believe that we're seeing a =
>related problem. While we're not seeing a white residue, we are seeing a
=
>problem with laser etched devices. We use thermally-screened devices on =
>certain products. Our screening house uses a yellow epoxy dot on the =
corner
>of the device to signify successful screening, but these dots have = been
>falling off of the laser etched parts. We suspect that the laser is =
>modifying the surface of the devices somehow (redeposition of carbon,
perha=
>ps?) to cause this.
>
>Any thoughts on how to either clean the device surface or come up with an
=
>alternative, inexpensive way to mark these devices?
>
>Greg Bartlett
>Mercury Computer Systems
>Chelmsford, MA
>[log in to unmask]
>
>--------------------------------------
>From: Dill, Norm J
>
>After cleaning (soap & water) soldered assemblies, has anyone had a white
>residue problem that was traced back to the laser etched characters = on
>plastic DIP's?
>We currently have a white residue problem under investigation where = the
>initial evidence indicates the source to be a certain brand of DIP IC. =
The
>top of the DIP has laser etched character markings that appear to leach a
>chemical component(s) that combines with the rinse (tap) water to form a
white
>residue after drying. The residue is easily removed with a cotton swab
and
>alcohol.
>At this point the complaint is only visual and easily corrected by hand
>cleaning but the concerns are what is actually being deposited on the =
>
>board surface and is it being completely removed.
>Any inputs on this will be greatly appreciated.
>
>Norm Dill
>Harris RF Communications
>[log in to unmask]
>
|
