Browse Prior Art Database

SEALANT MACHINE FEATURING A UNIQUE HOLDING FINGER AND SENSOR

IP.com Disclosure Number: IPCOM000006325D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2001-Dec-25
Document File: 2 page(s) / 115K

Publishing Venue

Motorola

Related People

Marty Briehl: AUTHOR

Abstract

The SSOVP sealant machine is a customized machine designed and built by the DMTG Equipment Engineering Department to both apply a silicone seal- ant to the Solid State Over Protection (SSOVP) device, and to cure the sealant using ultraviolet light. The sili- cone sealant is used to protect the semiconductor chip from moisture and contamination which would other- wise adversely effect device reliability or performance.

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MO7'OROLA INC. Technical Developments Volume 14 December 1991

SEALANT MACHINE FEATURING A UNIQUE HOLDING FINGER AND SENSOR

by Marty Briehl

decreased incidence of "wet sealant" rejects. The mechan- ical finger functions also as a sensor to detect the pres- ence or absence of parts.

  The design of such a holding finger presented sev- eral problems: (1) the fingers could not be in place dur- ing the pick up and unload portion of the cycle when the parts are taken out of, and replaced, in a 30 cavity

STATEMENT OF PROBLEM:

  The SSOVP sealant machine is a customized machine designed and built by the DMTG Equipment Engineering Department to both apply a silicone seal- ant to the Solid State Over Protection (SSOVP) device, and to cure the sealant using ultraviolet light. The sili- cone sealant is used to protect the semiconductor chip from moisture and contamination which would other- wise adversely effect device reliability or performance.

  When this machine was put into production in late 1990, we were experiencing a 15% to 20% yield loss due to a defect labeled "wet sealant:' Referring to Figure 1, we see that the SSOVP device, which consists of a die sandwiched between two nickel plated copper contacts, was held in place by a vacuum chuck during the sealant application and cure. There was a tendency for the wet sealant to be drawn between the chuck face and the contact under the innuence of the vacuum as shown by the path of wet sealant on the drawing. The seal behveen the chuck face and the contact did not prevent this from occurring. The wet sealant in the "crack" often was not fdy cured, so wet sealant was left on the device, creat- ing rejects. Also, some uncured silicone was sometimes left on the chuck, thereby contaminating other parts. Another problem we experienced was the poor reliabil- ity of the sensors that sensed the presence of the part. We were using an optical sensor that "looked" at the part in the chuck. These optical sensors were ditXcult to keep adjusted since the target (i.e. the device) was so small. If these sensors failed to sense a device, it was not properly coated which resulted in an additional reject. This type of reject ranged between 3% and 5%. Both of these defects had to be removed manually using a micro- scope which is a very labor intensive and costly activity.

SOLUTION:

  The solution to both of these reject problems was shown to be a mechanical tinge* that held the device on the chuck during the silicone dispense and cure cycles, allowing the vacuum to be turned off, resulting in the

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VlEU OF HOLDLNG FI.NCER 1N BOTH POSITIOHS

FIG 2

e Motorola,...