Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
  • G01R31/26—Testing of individual semiconductor devices
  • G01R31/2642—Testing semiconductor operation lifetime or reliability, e.g. by accelerated life tests
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D17/00—Separation of liquids, not provided for elsewhere, e.g. by thermal diffusion
  • B01D17/02—Separation of non-miscible liquids
  • B01D17/0208—Separation of non-miscible liquids by sedimentation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D17/00—Separation of liquids, not provided for elsewhere, e.g. by thermal diffusion
  • B01D17/02—Separation of non-miscible liquids
  • B01D17/0208—Separation of non-miscible liquids by sedimentation
  • B01D17/0214—Separation of non-miscible liquids by sedimentation with removal of one of the phases

Definitions

• Semiconductor devices such as discrete transistors and integrated circuits have time and temperature dependant failure mechanisms that occur at a high percentage rate during the first year of regular service. Thereafter, the surviving devices exhibit * a low and relatively constant failure rate over the remainder of their useful lives of many years.
• the heat exchange medium typically is 10 that known under the trademark Fluorinert liquid FC-40 manufactured by 3M Commercial Chemicals Division and is well known to be non- reactive and electrically insulating in such an environment.
• This medium has a specific 15 gravity greater than water, a specific heat greater than air and is selected to have a boiling point greater than the elevated temperature at which the burn-in procedure is effected.
• Other silicone based liquid mediums 20 also can be used.
• the Fluorinert medium must be controlled in temperature by a heater to raise the medium to the desired elevated- temperature for effecting the burn-in procedure and by a cooler, such as a mechanical refrigeration
• filtration must be provided to remove particulate and chemical contaminants, such as solder flux, debris and acids, introduced into or produced in the bath medium.
• Such a burn-in apparatus should have a bath tank large enough to facilitate burn-in procedures of production quantities of semiconductor devices and be self contained upon connection to an electrical power supply.
• the apparatus should also provide easy circuit card handling.
• movable racks in the tank chamber serve to lower and raise the circuit cards into and out of the liquid medium.
• This structure in combination provides a burn-in apparatus or unit that is efficient in conserving the expensive liquid Fluorinert 5 medium, and that is self contained upon connection to an electrical power source.
• each of the described systems have structure particularly suited to achieve the beneficial results of the burn-in apparatus ⁇ • - 0 with the liquid medium.
• a cartridge or coil electrical heater extends into the counterflow tube to raise the medium temperature to the desired elevated temperature.
• the pump assembly includes a lead screw/nut arrangement to obtain a variable speed impeller rotation with a fixed speed electric motor to accommodate changes in medium viscosity at various medium temperatures.
• Figure 5 is a fragmentary side elevation view of the pump motor mounting structure, taken partly in section along the line 5-5 of Figure 4 and in the direction 15 indicated by the arrows;
• Figure 6 is a rear elevation view of a heat exchanger tank of the invention.
• Controls and indicators of the burn-in procedure are available on the front of the control housing 30 and the unit can be moved on the casters 24 to suitable locations in a
• a vapor recovery system 66 comprises a vapor recovery condensor 68 and a liquid water separator 70. Gases including air, water vapor and medium vapor are exhausted from the tank 38 to the condensor 68 through duct 72. These gases, less the condensed water and medium vapors, are fed back to the tank in duct 74. The object of this recovery system 66 is conserving the supply of the expensive heat exchange medium.
• tank 38 has a rear wall 90, two side walls 48 and 94, a bottom wall 96 and a front wall 98.
• Tank 38 thus defines the burn-in chamber 40 that is -closed on five sides by tank walls and is open to the top to be closed by cover 34.
• Cover 34 has five segments 34A through 34E that individually can be raised and lowered over the chamber 40 hinged at the rear wall 90 of the tank. The cover segments are arranged to be aligned with the racks and circuit cards carried by the racks for access to individual racks by raising individual cover segments.
• cover segment 34C is aligned directly above rack 42C carrying cards 46C while cover segment 34D is arranged aligned above rack 42D carrying cards 46D.
• Burn-in chamber 40 contains in subtantially its bottom half, the liquid heat exchange medium 42 previously generally described to be the Fluorinert perfluorinated hydrocarbons manufactured by the 3M Corporation.
• the heat exchange medium has a specific heat greater than air, a specific gravity greater than liquid water and a boiling point or temperature greater than the elevated temperature at which the burn-in procedure is to be effected.
• the upper half or space 52 of chamber 40 is filled with ambient gases that can include water vapor and especially during a burn-in procedure can include Fluorinert medium vapor.
• the Fluorinert medium has a low evaporation rate at room temperature that increases markedly at the elevated temperature of a burn-in procedure.
• the racks 44 are in the lowered . position to place their circuit cards 46 and the carried semiconductor devices in the medium 42 in the bottom half 100 of the chamber 40.
• the racks' 44 hold the cards 46 in the top half space 52 of the chamber.
• the movements of the racks 44 are by means such as a hydraulic or pneumatic cylinder 101 connected with shaft 102 which in turn carries the racks 44.
• Shaft 102 then is vertically movable into and out of the pneumatic or hydraulic cylinder 101.
• the remaining stripped gases exit from the vapor recovery condensor 68 through return duct 74 into feed manifold 192 wherefrom they are fed into the upper space 52 of chamber 40 through the feed ducts 196 opening through wall 48 at openings 50. Thereafter the stripped gases pass through the length of the chamber 40 between walls 48 and 94 back to the exhaust ducts 194 picking up vapors to complete one cycle.
• the exhaust manifold 190 comprises an outer cylindrical housing 210 closed at one end by a plate 212 and at the other end by the fan assembly 198.
• the exhaust ducts 194 extend horizontally from the side wall 94 of tank 38 and are bent at a 90° angle to meet the cylindrical housing 210 vertically. The exhaust ducts 194 thus place the interior 214 of the cylindrical housing in gaseous fluid- communication with the burn-in chamber 40 interior tank 38.
• the impeller 236 of the fan assembly 198 withdraws gases from the opening 232 into space 244 and forces them into duct 72. This in turn draws gases including water vapor and medium vapor from the upper space 52 of chamber 40 through the exhaust duct 194 to the interior 214 of the cylindrical housing 210. Therefrom the gases pass through fine openings (not shown) in the cylindrical member 220 into close contact with the acid absorbing material 226 in the annular space 224. This removes hydrofluoric acid vapors and makes the water vapor alkaline. The remaining gases and vapors pass through additional fine openings (not shown) in the inner cylindrical member 222 and into the space 230 interior of the cylindrical member 222.
• Liquid water separator 70 further comprises a pair of electrodes 282 and 284 each connected to a bridge circuit 286 by conductor leads 288 and 290.
• the electrodes 282 and 284 extend radially through the wall of the housing 264 at a certain level so that their tips 292 and 294 are in fluid communication with any liquids or gases in the separator chamber 278 interior of the housing 264.
• the flow of intermixed liquid into the liquid water separator 70 is minimal and provides for the liquid substantially to rest in chamber 278 for the lighter specific density liquid water to rise and float above the heavier specific density heat exchange medium.
• This separation of the liquid water from the liquid medium aids in reducing the quantity of hydrofluoric acid formed in the tank 38, increasing the life of the tank and related pipes, ducts and conduits.
• the well 280 serves to contain the diffuser means 282
• the well 271 serves another, equally important purpose. There is a substantial distance between the outlet port 300 in the bottom of well 271 through base 274 and the level of the two electrode tips 292 and 294 indicated by the water/medium interface 296.

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• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Physics & Mathematics (AREA)
• Testing Of Individual Semiconductor Devices (AREA)

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Publications (2)

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Citations (13)

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• 1986
  • 1986-01-16 WO PCT/US1986/000070 patent/WO1986007158A1/en not_active Application Discontinuation
  • 1986-01-16 EP EP19860900933 patent/EP0225328A4/de not_active Withdrawn
  • 1986-05-20 GB GB08612184A patent/GB2175445B/en not_active Expired
• 1988
  • 1988-12-15 SG SG876/88A patent/SG87688G/en unknown

Patent Citations (13)

Non-Patent Citations (4)

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