50-06001.01 (PSAE2-201.10)modified 30 April, 2003
DateInitialsOperation
Rev. / ECO / Description / Checked / Approval / Date01 / 50-021 / Initial Release / M. Smith
Procedure for Picture
Focal Plane Assembly
50-06001.01
Revision 01
7/14/05
1/3/2003ADP
Assemble Focal Plane Array
Materials:
•Bench ionizer
•Wrist strap
•100% Nitrile, powder free Anti-Static gloves
•Sheldahl Aluminaized Kapton tape, P/N G401000
•X-Acto knife with #11 blade
•Hysol EA 9394 adhesive
•GE RTV 566
•Ablestik ECF-550 adhesive sheet
•Dow Corning Silane Z-6032
•Panduit cable ties, PLTIM-M76
•Amp connector P/N 311P409-1P-B-12
•Heatsink/TEC assembly B458993
•Detector assembly D458992
•Standoff C458995-3
•Connector bracket B458995-2
•Minco RTD P/N S651PDX24A
•Torlon washer B458995-5
•Amp jackpost assembly P/N M24308/26-1
•Blank alumina substrate P/N 458990
•Standoff Collars P/N 458995-7, 458995-8, 458995-9
CAUTION:
A WRIST STRAP MUST BE WORN WHENEVER A DETECTOR IS BEING HANDLED OR IS MATED TO A PART BEING HANDLED. THE WORK SHOULD BE PERFORMED IN FRONT OF A BENCH IONIZER WHENEVER POSSIBLE.
PREPARE HEATSINK AND TEC
______Record the serial number of the TEC and the heatsink assembly:
TEC Serial Number: ______
Heatsink Serial Number: ______
Detector S/N: ______
______Form the leads exiting the TEC at the point that they enter the wire guide slot. Use a pair of rounded nose pliers to hold the wire lead exiting the TEC so that the solder joint to the TEC is not unduly stressed during this lead forming operation.
______Mix a batch of EA 9394 adhesive per manufacturer’s instructions (10 grams of Part A to 1.7 grams of part B).
______Secure the TEC wires in place with a small dab of epoxy where the black wire first touches the heatsink and a small dab worked down into the slot where the wires enter the slot. Be sure that the staking material will not interfere with the collar that will be mounted in this area soon.
______Allow to cure for a minimum of 18 hours at room temperature.
______Mask off the TEC to prevent contamination during the addition of tapped holes.
______Add the nine 4-40 tapped holes (if not already installed) for the collar mounting.
______Tap the nine 4-40 holes required for the collar mounting.
______Remove masking materials.
PREPARE THERMAL STANDOFFS
______Measure the height of the top surface of the TEC relative to the heatsink surface that will receive the thermal standoffs. The thermal standoffs should be trimmed to be 0.006” shorter than the TEC/Heatsink height.
TEC height above heatsink = ______
0.006”
Calculated length of standoffs = ______
______Have three of the standoffs (C458995-3) machined to the appropriate length. The machining must be done either dry or using alcohol or water. No machining oils are allowed. The length tolerance is +/- 0.001”.
______Verify that there are no burrs on the top face of the standoff.
______Measure the length of each standoff using a height gage, electronic gage head, and surface plate. Rework or replace any piece that is not within the specified +/-0.001” tolerance. An easy and accurate way to do this is to install the standoffs onto the alumina substrate, place it upside down on a surface plate, and measure from the alumina to the standoff flange. Limit standoff screw torque to 36 in-oz.
Standoff #1 length = ______
Standoff #2 length = ______
Standoff #3 length = ______
______Wipe down the standoffs with a 2-propoanl moistened clean room cloth.
______Use the vapor degreaser in room I-209 with a minimum of 2 cycles through the vapor.
______Ultrasonic clean for 5 minutes in a 2-propanol bath.
______Very lightly dress the flange end of the standoff on 600 grit sandpaper supported on a surface plate.
______Wipe down the flange end of the standoff with a 2-propoanl moistened clean room cloth.
______Use the vapor degreaser in room I-209 with a minimum of 2 cycles through the vapor.
______Ultrasonic clean for 5 minutes in a 2-propanol bath.
______Dry the standoffs for 1 hour at 100°C in the class 100 drying oven.
INSTALL HEATSINK’S RTD, WIRE TEC, and RTD
______Clean the area where the RTD is to be installed by wiping with cotton swabs moistened with alcohol. Abrade the area with 600 grit wet or dry sandpaper. Rewipe the area with cotton swabs moistened with alcohol to remove particulate.
______Mask off the area where the RTD is to be mounted using 3M ESD tape. Leave approximately 0.030” clearance around perimeter. Locate RTD per drawing S458995.
______Clean the RTD mounting surface of the RTD (Minco P/N S651PDX24A) by wiping with cotton swabs moistened with alcohol.
______Locate two pieces of 0.006” diameter across the bond area (transverse to the lead wires) and secure with 3M ESD tape.
______Mix a batch of EA 9394 adhesive per manufacturer’s instructions (10 grams of Part A to 1.7 grams of part B).
______Apply a thin layer of adhesive to the heatsink and work it into the surface. Do the same on the mounting surface of the RTD. Verify that there is a small amount of squeeze out when the RTD is pressed into place with a cotton tipped swab. Wipe up excess squeeze out.
______Secure the RTD with a piece of 3M ESD tape.
______Form the leads exiting the RTD per drawing LL S-458995.
______Place a 2 in3 steel weight on top of the RTD to ensure it is registered against the 0.006” diameter wires.
______Stake the wires exiting the RTD to the heatsink approximately 3/8” from the RTD.
______Allow to cure for a minimum of 18 hours at room temperature.
______Remove weight and tape. Trim 0.006” diameter wires flush with the edges of the RTD with an X-Acto knife.
______Install the connector plate (B458995-2) using 2 4-40 x 5/16” screws. Torque to 8 in-lbs.
______Install subminiature D style connector (Amp connector P/N 311P409-1P-B-12) using two jackpost assemblies (Amp jackpost assembly P/N M24308/26-1). Torque to 48 in-oz.
______Form the leads service leads from the wires exiting the RTD per drawing LL S-458995. Tape in place.
______Mix a batch of EA 9394 adhesive per manufacturer’s instructions (10 grams of Part A to 1.7 grams of part B).
______Stake both ends of the RTD’s shrink tubing to the heatsink and run a second line of adhesive across the thin RTD leads near the point that they form a “U” turn.
______Allow to cure for a minimum of 18 hours at room temperature.
______Remove tape securing wires in place.
______Wire the TEC and RTD to the connector per CSR’s drawing 3005021.03. The RTD leads require in-line splices to 24 AWG multistrand Teflon insulated wire per MIL-W-22759/11.
______Measure the TEC impedance using an HP impedance analyzer. The nominal impedance at 1 kHz is 10.7 .
Measured TEC impedance: ______.
______Measure the resistance of the heastsink mounted RTD using a standard DVM. The nominal value at 70° F is 111.
Measured RTD resistance: ______.
______Secure the wires to the connector plate using two small Panduit 1/8” cable ties (PLTIM-M76). The locking feature should be on the top side (TEC side) to provide clearance with the flexprint rigid end.
______Measure the TEC impedance using an HP impedance analyzer. The nominal impedance at 100 kHz is 10.7 .
Measured TEC impedance: ______.
______Measure the resistance of the heastsink mounted RTD using a standard DVM. The nominal value at 70° F is 111.
Measured RTD resistance: ______.
BOND STANDOFFS IN PLACE
______Use a blank alumina substrate (P/N 458990) as a fixture to locate the three standoffs. Mount the three prepared standoffs to the substrate using 2-56 x 5/16 screws. The screws should have a short length of shrink tubing installed over the shank to force the screws to be centered in the alumina’s holes. Set the clocking position of each of the standoffs per drawing 458995.
______Cut a small piece (1/2” x 2’) piece of 0.001” thick plastic shim stock and place on the bottom of the alumina in the area where the TEC will interface. Use tape to secure shim in place.
______Clean the three areas that will have standoffs bonded to them by wiping with cotton swabs moistened with Tricoethylene.
______Follow immediately with cotton swabs moistened with acetone.
______Follow immediately with a cotton swabs moistened with 2-Proponal.
______Blow dry with an ionized nitrogen gas blow off gun.
______Mix up a solution of acid to etch the bond areas. Mix 6.6 parts by weight (pbw) of sodium dichromate with 66 pbw of sulfuric acid with 100 pbw of DI H2O. Mix thoroughly then allow to cool to room temperature (about 1 hour).
______Make an acid brush from the selvage of some fiberglass cloth rolled up into a 3/8” diameter cylinder and held with a battery clip.
______Form a small puddle of the acid on the heatsink at each of the three locations where a standoff will be bonded. The etched area should be slightly (1/8” per side) larger than the bond area. Don’t make the puddle so large that it runs down the tapped holes.
______Allow the acid to sit undisturbed for 120 seconds.
______Rinse thoroughly with fresh DI water for a minimum of 1 minute. Use a strip of acid paper to determine the acidity of the effluent. Continue to rinse if acidity is less than pH6.
______Perform a water break test on the three bond areas using DI water. Consult cognizant engineer if the part fails the water break test at any of the three bond areas.
Water break test results: ______
______Dry the part by wiping with a clean room cloth. Do not use line compressed air or bottled “air”. Both have significant chances of being contaminated, and we don’t want that, now do we?
______Mix a batch of Silane per Lincoln Laboratory PS-4-10, section 6.1.
______Apply a very thin coat of Silane in each of the three bond areas using an artist’s brush that has been cleaned in acetone and thoroughly dried. The swipes should start outside the bond area and end outside the bond area on the opposite side. If more than one pass is required to cover the complete area, minimal overlap should be used.
______Allow to dry for a minimum of 1 hour at room temperature.
______Place the heatsink in the class 100 drying oven in room I–209 with the oven powered down and at room temperature. Set temperature controller to 100 °C. Note the time that the oven reaches 100°C and leave the oven powered up for an additional 10 minutes. Open the door slightly and turn off the oven to allow the heatsink to slowly cool back down to room temperature.
______Install the detector alignment fixture (SK-ASE2-6) onto the heatsink supported on the assembly fixture (SK-ASE2-5)
______Install the alumina/standoffs onto the heatsink.
______Nominally there should be an 0.007” gap under each of the standoffs. Place a 0.006” diameter wire under each standoff and secure the wire in place with 3M ESD tape.
______Use an electronic gage head to verify that there is no tipping when the 0.001” shim is removed from the top of the TEC. Select larger or smaller wire diameter as required. The minimum allowable wire diameter is 0.005” and the maximum allowed is 0.010”.
______Mix a batch of EA 9394 adhesive per manufacturer’s instructions (10 grams of Part A to 1.7 grams of part B).
______Apply a small bead of EA 9394 adhesive to the base of each standoff using the handle of a cotton swab shaped into a flat blade.
______Verify that the 0.001” shim is still on the bottom of the alumina substrate. Locate the alumina/standoffs using the alignment fixture and allow the adhesive to transfer to the heatsink. Lift the alumina/standoffs off of the heatsink.
______Add or remove adhesive as necessary to result in a slight amount of squeeze out around the entire perimeter and full wetting of the standoff bond surface. Work the adhesive into the heatsink and standoff surfaces prior to the final iteration of adjusting the adhesive quantity.
______Once the adhesive quantity has been properly adjusted, install the alumina/standoffs and place a 2 cubic inch steel weight over the TEC to ensure that the alumina is firmly pressed against the shim on top of the TEC.
______Wipe the excessive squeeze out from around the bases of the standoffs using small polyethylene swabs.
______Allow the adhesive to cure for a minimum of 18 hours at room temperature.
______Remove the 0.001” shim, alignment fixture and tape from bond wires.
______Oven cure the assembly at 60°C for 1 hour. Load the part in the oven prior to powering up the oven. Start timing the bake once the oven gets up to 60°C.
______Cool the assembly in the oven by turning off the power to the oven, opening the door slightly and running the nitrogen purge at full scale.
______Place the heatsink/assembly stand on a leveling plate and level the top surface of the alumina.
______Remove the alumina from the standoffs.
______Measure the heights of the three standoffs relative to the top of the TEC by using a height gage and electronic gage head. Zero the instruments on the top of the TEC’s center.
Standoff #1 height = ______(left of flexprint)
Standoff #2 height = ______(right of flexprint)
Standoff #3 height = ______(opposite flexprint)
______Install the three collars using NAS 1352C04-4 (4-40 x 1/4” SHCS) using the “peep holes” and the annular clearance between the thermal standoff and the central hole to align the collar to the standoff. Torque the screws to 10 in-lbs.
______Mix a batch of EA 9394 adhesive per manufacturer’s instructions (10 grams of Part A to 1.7 grams of part B).
______Load the epoxy into a syringe used with the Norlico 2000XL pneumatic dispenser. Attach a #18 hypodermic needle (green housing) to the syringe. Set the dispenser controls for 21 psi and continuous operation. The Maximum working time is approximately 45 minutes.
______Inject the epoxy into each of the injection holes with the hypodermic needle bottomed out against the top of the collar flange (to encourage circumferential flow) until the adhesive squeezes out between the standoff post and the collar central hole. When complete, there should be a continuous bead of adhesive around the standoff post. Continue to dispense glue as the needle is retracted from the injection hole to prevent sucking the glue out of the interior volumes.
______Wipe off excessive glue using clean room swabs.
______Stake collar screws.
______Allow adhesive to cure for 18 hours at room temperature.
______Apply a piece of low-e thermal tape applied around the body of each thermal standoff. Use the tape template (0.315” x 0.880”) to cut a piece of the low-e tape (Sheldahl P/N G401000). Use a sharp #11 blade in an X–Acto knife handle to cut the tape. Inspect the edge of the tape for any balled up adhesive and remove if found.
______Cut a vent hole in the low-e tape over each of the two vent holes on each standoff by poking with sharpened stick.
INSTALL DETECTOR
______Record the S/N of the device to be installed here and on the first page of this form.
Device S/N: ______
______Verify that the RTV thickness will be correct with this detector substrate. Place a 0.0005” thick shim over the TEC and install the detector substrate with the three 2-56 x 5/16” long screws torqued to 36 in-oz. Each screw should have a Torlon washer (B458995-5). Verify that the shim readily slides out. Verify that a 0.002” thick shim can not be slid into the gap between the TEC and the detector substrate.
______Clean the area on the bottom side of the detector substrate that will be located above the TEC by wiping with separate cotton swabs moistened with Tricoethylene, acetone, and 2-Proponal.
______Clean the top of the TEC by wiping with separate cotton swabs moistened with Tricoethylene, acetone, and 2-Proponal.
______Install detector alignment fixture again.
______Mix a batch of GE RTV-566 using a pre-measured bi-pack.
______Spread a thin layer of RTV on the top of the TEC using a sharpened wooden handle from a cotton swab. Verify that the proper amount of RTV is present by installing the detector and torqueing the three mounting screws to 36 in-oz. Remove the detector and look for full wetting of the interface and not too much squeeze-out. Iterate as required. Once the correct amount is verified, add a small dab in the center of the TEC and install for the final time.
______Wipe off excessive RTV around the TEC top plate perimeter by using small polyethylene swabs. A small bead is acceptable if there is no chance that it will cause shorting of the TEC elements.
______Remove the detector installation fixture.
______Install the flexprint connector onto the connector plate using two 2-56 x 3/16” screws torqued to 48 in-oz
______Install flexprint thermal standoffs (C458995-3) using 2-56 x 5/8” screws and Torlon washers (B458995-5). Torque to 48 in-oz.
______Mix a batch of EA 9394 adhesive per manufacturer’s instructions (10 grams of Part A to 1.7 grams of part B).
______Stake the following hardware and features:
___ Top of standoff screws to detector substrate
___ Standoff to bottom of alumina substrate
___ Positronic to connector plate 2-56 screws
___ Connector plate to heatsink screws
___ RTD/TEC connector jackposts and nuts
___ Positronics to flexprint mounting hardware
___ Flexprint screws to flexprint cross bar
______Allow to cure for a minimum of 18 hours.
______Oven cure the assembly at 60°C for 1 hour. Load the part in the oven prior to powering up the oven. Start timing the bake once the oven gets up to 60°C.
______Cool the assembly in the oven by turning off the power to the oven, opening the door slightly and running the nitrogen purge at full scale.
______Photograph the top and bottom sides of the focal plane assembly. A label designating the heatsink and detector serial number should be in each photograph. Try to document the staking of each screw and the condition of each bond wire.
______Measure the resistances shown in the table below: Use test cable with a flight grade connector for probing the RTD/TEC connector.
Pins / Nominal / Actual5-9 / 111
4-8 / 111
4-5 / 0
8-9 / 0
1-6 / 10.7*
*Impedance at 1 kHz with HP Impedance Analyzer
______Use the class 100 nitrogen purged bake-out oven to bake the FPA at 60°C immediately prior to vacuum bake.
______Vacuum bake the focal plane array at 60°C for a minimum of 48 hours. Verify cleanliness with the TQCM and RGA.
Vacuum bake-out log number: ______
Sensor base S/N ______
Final total pressure ______torr
______Inspect the sensor base and FPA under black light to verify that no loose particulate is present. Blow off with ionized N2 or vacuum off as appropriate.
______Install the connector savers to both fo the sensor base connectors. Torque screws to 48 in-oz.
______Verify that the detector harness has a shorting plug installed.
______Weigh the focal plane assembly while still on its handling fixture and with the shorting plug installed.
Weight of FPA ______grams (with fixture and shorting plug).
Weight of fixture and shorting plug ______grams
Weight of FPA ______grams.
= ______lbs
INSTALL HEATSINK INTO SENSOR BASE
______Scribe the centerlines of the two “Bonnet Pins” using a height gage fitted with a scribe marker.
______Scribe the radiation shield even with the frame store shield and 0.150” in from each edge using a height gage fitted with a scribe marker.