Differences

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--- bonding:ball [2018/04/28 18:16] – [Capillary cleaning] mcmaster
+++ bonding:ball [2019/03/05 00:15] (current) – removed mcmaster
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-====== Introduction ======
-Thermosonic ball bonding is the most common and cost effective method for general use on modern ICs.
-  - The wire is fed through a ceramic capillary, shaped somewhat like the end of a cheap mechanical pencil (fat cylinder with a thin cylinder on the end)
-  - The tip of the wire is melted by an electric arc (negative electric flame-off or NEFO, the most common process) or hydrogen flame (in older bonders, or highly ESD-sensitive applications) and surface tension forms a ball
-  - The capillary is lowered onto the pad and squishes the ball onto the pad. Ultrasound and heat are used to form a solid connection
-  - The second bond (from the wire to the leadframe) is normally very similar to a wedge bond but has a semi-circular or ring shape as it is formed by the side of the capillary
-====== First bond ======
-Overhead shots typically look like this (Photobit camera sensor, focal plane on pad)
-{{:zoidberg:ball_bond_01_neo20x_cropped.jpg?300}}
-or this (focal plane on ball)
-{{:zoidberg:ball_bond_02_neo20x_cropped.jpg?300}}
-Angled SEM image of ball bond (Samsung 16-mbit DRAM). Image copyright 1998-2009 Smithsonian Institution; used by [[archive>smithsonian|permission]].
-{{:smithsonian:ball_bond.jpg?300}}
-====== Second bond ======
-Test bonds on gold package pad (from AZ's training)
-{{:bonding:second-bond.jpg?500|}}
-====== Capillary cleaning ======
-SPT Capillary Unplugging Wires (CUW) tool
-  * http://www.epakelectronics.com/spt_capillaries_cuw.htm
-  * http://www.epakelectronics.com/pdf/spt/SPT-CAP-CUW-Brochure.pdf
-  * Haven't tested
-  * My capillary is something like 1.6 mil => 40 um => CUW-35 reccomended
-  * Note 1 mil wire => 25 um
-https://patents.google.com/patent/US20020096187A1/en
-  * Pretty boring
-  * Says poke it with a wire, ultrasonically clean it, and maybe sand the tip
-  * Duh..this is what I tried before looking. Although I don't have a fine enough wire on hand
-A few sources hint at methanol as the preferred cleaning agent
-https://www.ebay.com/itm/CROSSHAIR-WIRE-FINE-TUNGSTEN-WIRE-FOR-SCOPES-AND-TRANSITS-0125mm-0005/321070292094?hash=item4ac147dc7e:g:v-wAAMXQ2UVQ9N2j
-  * CROSSHAIR WIRE FINE TUNGSTEN WIRE FOR SCOPES AND TRANSITS .0125mm/.0005"
-  * Smaller than I wanted, but eh lets give it a try since its so inexpensive