Browse Prior Art Database

SNAP CURE CAPPING FIXTURE

IP.com Disclosure Number: IPCOM000008541D
Original Publication Date: 1998-Mar-01
Included in the Prior Art Database: 2002-Jun-21
Document File: 3 page(s) / 154K

Publishing Venue

Motorola

Related People

Huzainor Hamzah: AUTHOR

Abstract

RFSOE products are encapped with a ceramic lid which is coated with epoxy sealing material on its lip. The encapsulation or capping process presently has several issues. Firstly, they are several types of epoxy which require several ways of capping method. Secondly, gross leak failure rate is quite high (-10%). Thirdly, several customers who use some of these products have been experiencing solder seepage during their solder reflow process, Solder seepage is where solder seeps through the epoxy and damages the device. A study on this issue has shown that the sealing strength of the epoxy is weakened when it is exposed to high solder fluid temperature. Finally, the RFSOE production line is moving towards automated processes where reduc- tion in process cycle time is one of the critical requirements. This will be very difficult to achieve with the current capping process.

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MOTOROLA Technical Developments

SNAdCURE CAPPING FIXTURE

by Huzainor Hamzah

BACKGROUND

  RFSOE products are encapped with a ceramic lid which is coated with epoxy sealing material on its lip. The encapsulation or capping process presently has several issues. Firstly, they are several types of epoxy which require several ways of capping method. Secondly, gross leak failure rate is quite high (-10%). Thirdly, several customers who use some of these products have been experiencing solder seepage during their solder reflow process, Solder seepage is where solder seeps through the epoxy and damages the device. A study on this issue has shown that the sealing strength of the epoxy is weakened when it is exposed to high solder fluid temperature. Finally, the RFSOE production line is moving towards automated processes where reduc- tion in process cycle time is one of the critical requirements. This will be very difficult to achieve with the current capping process.

  To reduce the effect of all the issues detailed above, a fast-cure epoxy which has high resistivity to solder reflow temperature has recently been successfully developed. Using automated capping machine devices that were encapsulated using the fast cure epoxy did not show evidence of solder seepage after 10 cycles of dipping the encapsulated devices in solder having a temperature of 285°C. However, in the manual encapsulation process

where encapsulated devices were cured in an oven for 30 minutes while being held in a three-piece pressure fixture, solder seepage of up to 100% was detected.

SOLUTION

  Further studies showed that slow temperature ramp-up in the oven used in the manual process was the reason for reduced epoxy strength experienced in the manual encapsulation process. In the auto- mated process two-stage heating, a first tacking stage, and a second curing stage, was used to heat up the epoxy to the desired curing temperature in a relatively short time. An evaluation which was conducted to determine the effectiveness of the tacking stage in producing high epoxy sealing strength showed that it is not a factor. More impor- tantly, the evaluation also revealed that devices could be encapsulated with high epoxy sealing strength by applying direct heat to the devices to raise the temperature from room temperature to the desired curing temperature with the same temperature ramp-up time as that of the automated process. This discovery has led to the design of a new three-piece pressure fixture with a heating component as illustrated in Figure 1, With this new fixture the higher epoxy sealing can be achieved in live minutes without the need for a conventional oven.

48 March 1998

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MOldRoLA Technical Developments

CONTROLLER

HEATERS

BUTTERFLY NUT w

SPRING PLATE L

CERAMIC LID WITH EPOXY

-- -a-

CAPLOCATOR D ..- .- _--. -- --. .-. .a PLATE

-

HEATER ELEMENTS

Fig. 1 Fig. 2

THE MACHINE

  In order to make the manu...