TE-1100 Test Fixture Kit Instructions Low Cost High PLow...

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Test Electronics, a leader in test fixture technology. Fabrication techniques to make engineering dreams come to life.

Updated Oct 2010. If this date is old, check for a newer version at http://www.testelectronics.com/bon.html

Non-copyright material, public domain.You are free to make as many copies as you like for any purpose.

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Step by step instructions, highly illustrated for the non-english speaking.Building a basic bed of nails fixture using a drill press and a few basic hand tools!

Fixture KitThe TE-1100 Bed ofNails test fixture kitis a product specifi-

TE-1100 8” x 15” Fixture KitShown above is a picture of the TE-1100 8x15 bed of nailsfixture kit as it appears when taken out of the box fromTest Electronics. These kits are available in sizes rangingfrom 8” to 24” wide. I am using the 8” wide version forthis example. The TE-1100 fixture kit includes:10) Threaded nylon press downs20) Nylon nuts1) Safety switch (detects cover closed position)Test pins and receptacles shown in the 4 yellow packetsmust be ordered seperately because the quantities vary forevery individual circuit board.

cally designed to make testfixture fabrication a possibil-ity in only 2 days withnothing more than a drillpress and a few hand tools.

These instructions will guideyou in detail through all thesteps required to build a highquality Bed of Nails TestFixture customized to test yourcircuit board.

Many small and medium sized electronic manufacturersdo not have a full blown CNC machine shop availableat their disposal. Typically the job of fixture fabricationis subcontracted to a local CNC machine shop. At themachine shop, you wait for the backlog, and you payset up charges, and you hope it comes out right. If itdoesn’t come out right the first time, you wait longer,and you pay more set up charges. All over again!Typical machine shop backlog can be anything between2-4 weeks. That is just too long to wait when you havea product that needs testing!

Experienced MachinistsEven if you are one of the lucky ones with a CNCmachine shop available at your disposal, and a topnotch machinist, browse through this anyway. We havebeen building fixtures since 1986 and may provide youwith many helpful inside tips that you can apply to yourCNC fabrication process.

Test pins andreceptacles shown in yellow

packets are ordered separately.

Circuit Boards to be TestedShown above is a picture of the circuit boards to be putunder test. I will use these boards to demonstratebuilding this test fixture. You will need 2 bare boardswhich must be expendable in the fabrication process,and one assembled board which will not be harmed.

http://www.testelectronics.com

http://www.testelectronics.com/1100press.htm

Test Electronics, a leader in test fixture technology. Providing the tools which make engineering dreams come to life.Updated Oct 2010. If this date is old, check for a newer version at http://www.testelectronics.com/bon.html






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Rear PanelShown here is therear panel. I hadpredeterminedthat I would needtwo 9pin female“D” connectors toconnect this testfixture to thecomputer.

rear panel and they also provide a labeled mylar overlay.This price beats the time I would spend scroll sawing andfine grinding the connector holes with a Dremel tool. Icould never match the esthetics of a nice printed mylaroverlay either. So, I just ordered my rear panel with thecutouts, overlay and $6 worth of connectors installed. Thefront and rear panels are made out of 1/16” Aluminum,which is very easy to cut if you rather not spend the $50.

Front Panel

I ordered the polished aluminum front panel. It was only$25. This is really just a pure personal preference. It justgives the test fixture a nice clean look in my opinion.

Test Electronics charges$50 to custom punch the

Aligning the Circuit BoardThis odd shaped board isa good example becauseit makes me show you allthe details. If your boardis perfectly rectangularcentering is simple. Butit is not hard with thisboard either. First, centerthe widest part of theboard. Then, slide the board straight back the mark the twocorners on the precision tape ruler.

Mark Corner #2

Mark Corner #1

Rear Panel

Front Panel

Find Center







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Marking the Top Cover

Align the Bare Board and Press Into Position

Peel off the Nonstick Tape Backing Adhere the Bare Board Firmly in Place

Next, simply transpose the marks to the top coverprecision tape ruler.

Mark the Top Cover







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Remove Press PlateYou can actually drilla fixture withoutremoving the pressplate Just open thepress plate, and tapeit open. However, it ismuch easier to handlethe fixture with thepress plate removed.The press plate is nothard to remove. Justunscrew the 6 screwsshown here.

Fixture

Preparing The Drill PressThe table on the drillpress as shown here ishard metal. Some drillpresses may havewooden or protectiveplastic tables.

To protect the fixture, I glue a piece of paper towel downon the table as shown below. This just protects fromscratching the bottom of the test fixture while working.3M spray adhesiveworks well. Use asparing amount. Justenough to hold thepaper towel downsecurely.

with press plate removed

Remove Top Cover

Drill Press Table

Paper Towel Covering Drill Press Table







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Drilling Tooling Pins

The first step is to drill the tooling pins. The tooling pinswill locate the board on the fixture. Tooling pins will bedescribed in more detail later. The tooling pin holes in thisboard are 1/8” Diameter. Using the circuit board as a drillguide, I use a 1/8” cobalt drill to drill two holes in adjacentcorners for the tooling pins. For a drill press, I recommendusing a Cobalt drill. A Machinists Handbook will tell you

Drilling the Second Tooling Pin HoleTo get a good tight press fit, drill the tooling pin hole usingthe same size drill bit as the tooling pin. The 1/4” G-10material drills small. This is because the glass fibers breakup as they are drilled and actually lift and stick out in thehole. This makes a perfect press fit for simple tooling pins.

If you want to make a removable pin which is captive witha screw or some method, ream the hole a full .0005”oversize. The tooling pin shown below would be anexample of a removable pin. Test Electronics can provideyou with tooling pins if you would rather not make themyourself. However, most sizes can be cut easily fromstandard drill rod. So, in this example I will show you howto make the tooling pins out of drill rod yourself.

Shown above is a sample of a more complex removabletooling pin supplied by Test Electronics. This is not usedin this fixture sample, but I will describe the use of largertooling pins in more detail later.

to use carbide for drilling G-10 material. Don’t do thisunless you have a very steady hand! Carbide drills are waytoo fragile for a drill press and will snap off leaving youstuck with drilling and plugging. Cobalt will last for atleast 30 holes. Just change bits when they dull.

Drilling First Tooling Pin Hole

1/8” Cobalt Drill







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Fabricating Tooling PinsThe toolingpin used in thisfixture will bea simplestraight pin cutfrom 1/8”diameter drillrod availablein all drillsizes fromyour localmachine toolsupply store.Some hard-ware storeseven stock it. Cut two pieces for two tooling pins. Theyshould be cut to 1” long.

Shaping Tooling PinsShaping the top of thetooling pins allow thecircuit board to fitsmoothly over thetooling pins. File thetops of the tooling pinsinto a dome shape. Putthe pin in a drill pressas pictured here. Spinand file to anice domeshape on thetip. Also, filethe base slightlyto allow the pinto be pressed inthe hole withoutbinding. The blackimage here shows theproper shape for asimple tooling pin.

Inserting the Tooling PinThe drill pressis OFF. Thespindle is notturning! Shownhere, the drillpress providesa convenientway to holdand insert thetooling pin intothe fixture. Thedrill pressholds thetooling pinperfectlyperpendicular.The moreperpendicular you can hold this tooling pin, the moreaccurate the test fixture will be. It is very important to holdthe tooling pins perpendicular and to not bend them whilepress fitting them into the bed of nails plate

Press Fit Tooling PinHere is a close up view ofthe tooling pin after it ispress fit into the fixture.Notice the nice dome shapedtop. This allows the circuitboard to self align easilywhen the test technician putsthe circuit board under teston the fixture.

Basic Tooling Pin Drawing

Hack saw tooling pin

Shaping Tooling Pins

Pressing Tooling Pin

Tooling Pin







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Adjusting Press DepthThe tooling pins should be pressed in flush with thebottom of the bed of nails plate. An easy way to do this isto remove a side plate and look in side to see how deep thepress went.

Removing Side Plate

Side Plate Removed

Pressing Far Right Tooling Pin Deeper

Hammering Near Left Tooling Pin Flush

In the picture above, the far right tooling pin was notpressed in deep enough. Then the near left tooling pin waspressed in a little to far. Shown above I am preparing tocorrect this by pressing the far right pin in just a littlefurther. Below shows hammering the near left tooling pinback up a little to make it flush. I used a large ratchetwrench ratchet. Any small heavy metal object will work.

Side Plate RemovedWith the side plate removed, it iseasy to view inside thefixture underneath the 1/4” G-10 bed of nails plate. Verifythat the tooling pins were pressed in to the properdepth.The bases of the tooling pins should be flush withthe bottom surface of the bed of nails plate.







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Removing the Bare BoardNext, remove thebare board andreplace it with a newbare board. Firstblow off all drillfilings so the tape isclean. Wedge ascrewdriver underthe board and pry itoff slowly.

There are twoimportant reasons forremoving the board.

When drilling the board, the sides may have been scorchedslightly as the blank board aligned the drill. Light scorch-ing is OK, but scorching does cause slight inaccuracies.The first reason for changing the board is to make sure thatthe pinning wasaccurate enough toallow the new boardto slide properly onthe tooling pinswithout binding.The second reasonis to prevent toler-ances from addingup, by removingstresses. The newbare board will selfalign to a slightlynew position guidedby the tooling pins.The new bare boardwill be used as thedrill template fordrilling the test pins.

Mark the Test Probe LocationsThe black dots onthis fresh new bareboard show thetest probe loca-tions that I plan todrill. Notice that Iput 5 dots aroundboth tooling pinholes. These aretest probes aroundthe tooling pins.

these probes are used simply for the force they provide.They keep the board from binding as it slides up thetooling pins. The exact locations are not critical.

Adhering the Marked Board

After marking the test probe locations, simply press thismarked bare board into place.

Bare Board

Remove Bare Board

Mark Test Probe Locations

New Bare Board

These probes are notused for electricalcontacts. Instead,







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Drilling the Test Probe HolesHere is whereyou see thebeauty andsimplicity inthis techniqueof using a bareboard as thedrill guide. Theholes in thebare boardactually act asa precisiontemplate whichguides the drillinto positionwith very highaccuracy. It isimportant to use a light touch here. To let everything slideinto position. Surface mount boards can be drilled thesame way. Simply center punch and predrill from the backside prior to adhering the board.

Finger DrillSometimes the righttool can really helpmake the job easy.This finger drill isnot necessary, butit is a handy toolthat allows moreprecise feed andpressure control.They cost about$300. Available atmost machine shopssupply stores.Shown here is a #30JO Albrecht KeylessChuck 0-1/8"Test Electronics part number TE-2823A1-3100A45.

Finished Drilling

This shows the board after pin drilling is complete. The bareboard is now scrap, but the test plate is now drilled to a veryhigh accuracy. An accuracy comparable to that of a CNCmachine. This is possible because the bare board which wasused as a drill template was fabricated with a CNC machine.

Removing the Bare BoardNext simplyremove thebare baordfrom the bedof nails plateby gentlyprying one ofthe corners upwith a flatblade screw-driver. Savethis bareboard forfabricatingthe pressplate.

#51 Cobalt Drill

Finger Drill Optional

Finished Drilling

Remove Bare Board







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Peel off and remove adhesive strip

Peel off and remove tape guide

Wipe excess adhesive off with isopropyl alcohol

Finished drilling for PCBoardThis finishes all the drilling for mounting this PCBoard.The next page is not necessary for most applications. Thenext page takes a step back, and shows how to drill thetooling pins if your pins are larger than 3/16” in diameter.







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3/16” and Larger Tooling PinsThis page is not necessary for mostapplications. This is required only forapplications where the tooling pin holesare larger than 3/16” in diameter. Toolingpin holes larger than 3/16” can not bedrilled using a standard 1/16” thick PCBoard as a drill guide.

In this example,the tooling pinhole diameter is0.2900”. So, a drillbushing is needed.Test Electronicscan lathe a custombushing to matchyour tooling pinhole and supply

Drill BushingHere is a closeup view of thedrill bushing.A 1/8” pilothole is drilledfollowed by a1/4” final holeto mount theguide pin.The guide pinbody size islathed to0.2895”.0.0005” underfor a nice slip fit in the 0.2900 tooling pin hole. Thesetooling pins and drill bushings can be custom made by TestElectronics.

Ø 0.2895”Ø 0.3125”

Ø 0.2495”6-32 Fillips Truss Head

Rounded Tip

Tooling Pin Close Up

Shown here, a flute angle of 135 degrees on a 3/16” drillraises the drill tip cutting edge distance up to the standardPCB thickness of 1/16”. As a result, larger size drills will

the bushing with the custom tooling pin. Or, you can do ityourself. Once the bushing is made, The drill bushing issimply pressed in the blank board and drilled as shownbelow.

Hole is too Large

1/8” Pilot Drill

Drill Bushing

not center properly.







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PC Board OverlayFabricating a PCBoard overlay is not a necessary step inthe fabrication of a test fixture. However, it does add anice professional touch to the job.The purpose of this PC Board overlay is simply a visualaid to make the test fixture more user friendly. When thetest technician sees this overlay, he will understand at aglance the proper way the circuit board should be orientedon the bed of nails tester. Your technician will also knowwhich product this test fixture is designed for. This helpswhen you have more than one bed of nails test fixture formore than one product.

Making an OverlayThis step usually requires adrive to your local copyshop. You need a scaleablecolor copy machine, adhe-sive backed paper, andadhesive backed clearpolycarbonate sheets. Thesesupplies are all available insmall quantities for areasonable price at mostcopy shops. I suggest goingto a copy shop rather than stocking these supplies.I will copy the bare board I used to drill the tooling pins.The copy should be scaled 1:1. You will need to use somemath to get this precise because copy machines are nothighly calibrated pieces of equipment. First set the copymachine to 100% and copy at least 10” of a 12” ruler.Next, measure the copy. The 10” mark on my copy mea-sured 9.65”. So, I set the copy machine to 1000/9.65 =103.6. I rounded and set my copy machine to 104%. Thisprovided a perfect 1:1 copy.Next, I copied the circuit board and checked the results.Then using adhesive backed paper, I made two copies ofthe bare board. Then I laminated these two copies with aprotective coating of clear adhesive back polycarbonate asshown above. The second copy is a spare in case I mess upcutting and punching. I recommend two copies as cheapinsurance to save a drive back to the copy shop.

Cutting and Marking HolesNext the overlay needs tobe cut and punched.Simply cut the overlaywith scissors. Next, asshown here, I marked theextra 5 holes I drillednear each of the toolingpins. I used the bareboard which was the testpin guide as a template for marking. Shown here is thisbare board laid over the overlay. Using a permanent finepoint marking pen, I marked the 5 holes around eachtooling pin. The normal through holes will be seen on thecopy and do not need to be marked.

Punching HolesUsing a 1/8” paper punch,simply punch out all thetooling pin holes, and thetest pin holes so theoverlay will fit over thetooling pins and not coverthe test pin holes. Asshown here.

Placing OverlayFinish by peelingoff the nonstickbacking. Thencarefully align theoverlay over thetooling pins. Gentlyslide the overlaydown so that itsticks evenly to thebed of nails plate.Smooth out any airbubbles and you arefinished. Finished Overlay

Cut Overlay

Punch Overlay

Marking Overlay







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Installing Receptacles

Shown here is the insertion toolrequired to install the test pinreceptacle shown below.The recommended method for installing these receptaclesis to first dial in the correct shoulder set height and ham-mer it in. In this project I set the receptacle height to0.200” Hammer the recep-tacle in place with a light tapwhile holding the toolperpendicular. As shownhere to the right. My handshould be in this pictureholding the test pin tool, butI had to stand to the side tomake way for the camera.This method works, butaccuracy is sacrificed. Theholes are drilled veryperpendicular and thereceptacles are rigid enoughto hold their perpendicular-ity fairly well, but they canbe bent. This methodtypically looses 10-20 mil ofaccuracy depending on howskilled you are. This is where a great deal of accuracy canbe lost in building your fixture. If your application canhandle this loss in pointing accuracy, then go ahead andhammer all the pins in. This method is fast and easy.

Using a Drill Press InsteadHere in the Test ElectronicsTest Fixture production line,we maintain a very high levelof accuracy using a CNCmachine to install the recep-tacles. You can get close to thisby using a drill press to pressin the receptacles. Finished View

Using a drill press tomaintain perpendicu-larity is a much bettermethod that I highlyrecommend.

Put the tool in thedrill press chuck andpress the receptacle inwith the drill press.This method ensuresexcellent perpendicu-larity.

Set the receptacle inthe hole, position theinsertion tool over thereceptacle, thengently press in place.Repeat for all thereceptacles you needto install.

Position Tool Over Pin

Press the Tool

Hammer Method

Press Method







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Installing Test PinsThe final step isto install the testpins into thereceptacles. Theprocess is simple.Put the test pin inthe receptacles asshown here. Usetweezers tohandle the testpins. This willprevent corrosives salts and acids on your skin fromdegrading the surface of the test pins.

Press the Test PinsPress the test pinsinto place usingone of the nylonpress rodssupplied with thefixture.Be sure to usethis rod oranother softplastic material.Avoid hardmetals. Hard metals will dull the tips of the probes.

Side View Test Pins in Place

Finish Bed of Nails Plate

Finished Bed of Nails Plate.

Verify Smooth Operation

Place the board under test on the bed of nails and visuallyinspect for proper fit and alignment.

View from the side to verify all pins are fully pressed intheir sockets.

Test Pins

Soft Insertion Tool

Side view Testing PCBoard Fit







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Test Pin Head StylesThere are a widevariety of test pinhead styles availableto cover most anyapplication. In thisfixture I used 3 headstyles.1. To probe thebottoms of connec-tors I used the #04Crown.

2. To probe solderpads and emptythrough holes I used#51 Blade.

3. The probes placedaround the toolingpins were a #51Blade with a mediumprobe force. 12oz

Probe head selectionvaries on manyfactors. Consult testelectronics technicalsupport for yourneeds.

Probe SizesTest probes are readily available in three sizes:

0.060 diameter body for probing points100mil center tocenter or larger.

0.040 diameter body for probing points 75 mil center tocenter

0.030 diameter body for probing points 50 mil center tocenter

Receptacle

Receptacles are available for all sized probes. Shown above isthe wire wrap version. Solder cups and crimp styles are alsoavailable. The wire wrapped version shown above are used mostof the time and will be used in this project.







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Fabricating the Press Plate

Find and mark goodlocations for the pressdown rods. These pressdown rods must clearcomponents and bespaced evenly along thetop surface of the board. Itis desirable to put thepress down rods neargroups of test pin loca-tions, but avoid puttingthe rods directly over thetest pins. Fixtures withpress rods placed directly

Fabricating the press plate is simple. Drill holes that coverthe area of the circuit board under test, and put thethreaded nylon press rods in.

Marking Rod Locations

over test pins will need special handling. You will not beable to close the fixture without a circuit board in placebecause the press rod will hit and could bend the test pins.

Here is a close up view of 8 locations I chose for 8 of thepress rods. I will only use 8 of the 10 press rods.

Marking the Bare BoardNext copythe 8 marksfrom thestuffed boardto a bareboard asshown here.This is alldone freehand as youare using youbest judg-ment tosimply makethese marksin clear areasand near but not on test pins. I used the bare board, whichwas previously drilled on the bed of nails plate so that Ican easily see all the test pin locations to avoid.

Adhere the Bare Board

Peel off the nonstick tape. Then align and adhere the blankboard to the press plate. Reference the precision tape rulerto align the board to the exact same location on the pressplate that the board was on the bed of nails plate.

Marking Rod Locations

Black Circles Mark Rod Locations

Transpose Marked Locations

Marked Bare Board on Press Plate







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Remove the Handle and PinRemovingthe handleand pin isnot neces-sary, buthelps keepthings flaton the drillpress table.Anothermethodwould be toreassemblethe pressplate on thetest fixture.I prefer towork withthe parts disassembled. It is easier to handle the light-weight cover rather than the whole test fixture.

Parts Removed and Ready

This shows the handle, latch pin, and safety switch pressrod removed, and circuit board adhered properly in placeready for drilling.

Drilling Press Plate

This shows drilling the press plate in the marked locations.All marked locations are drilled with a 1/8” cobalt drill.These are 1/8” pilot holes. It is important to use a smalldrill to avoid lifting the blank board off of the adhesivetape. This machining quality tape is very strong forholding forces parallel to the work surface, and evenperpendicular shock forces. However, as you know theboard can be pried up slowly with the constant force of aflat blade screwdriver. Larger drills will tend to pull burrsup between the clear polycarbonate press plate and theblank board. These burrs could slowly build up theconstant force necessary to lift the board. So, I recommendusing a 1/8” cobalt drill to make pilot holes. Then removethe board and drill through the pilot holes with the finaldrill size of you choice.

Temporarily Remove Parts

Parts Removed

Drilling 1/8” Pilot Holes







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Close Up of Pilot Holes

Close up view of all the pilot holes after drilling.

Remove Blank Board

Remove the bare board

Remove Tape and Ruler

Peel up the adhesive tape and peel off the ruler.

Cleanup

Wipe excess adhesive off with Isopropyl Alcohol.

Pilot Holes Drilled

Remove Bare Board

Remove Tape

Clean







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Drilling Out Pilot Holes

Drill out the pilot holes. There are two possible ways tomake a fixture. You can drill and tap the hole, or just drilla 1/4” hole which is large enough to slip the threaded pressrods through. There are 20 nuts supplied with the kit forthis purpose. I like to do the extra work of tapping becauseit makes it easier to adjust the press downs and level theboard after the fixture is assembled.

Drilling #8 and Tapping1/4-20

Tapping 1/4-20Hand tapping isperfectlyacceptable. Thepress plate isnot a superaccurate platelike the bed ofnails plate.Holding perfectPerpendicular-ity accuracy isnot such animportant issuein fabricatingthe press plate.However, there is a better way if you don’t mind investingin a tapping tool. The tapping tool will give better perpen-dicularity, a smoother tap, but most important, it will savetime when you have a lot of holes to tap.

Drilling

#8 Drill

1/4-20 Tap

1/4-20 Tapping Tool







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Debur

This shows a deburring tool used to clean up the tappedholes. Debur on both top and bottom sides.

Clean

Clean with Isopropyl Alcohol

ReassemblyReassemble pressplate to the fixturekit.

Insert Cover Closed Switch

Debur

Insert Cover Switch

Assemble







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Screw in the Press Rods

Adjust Press Rods

Set the press rod depth to compress the spring pins tobetween 1/2 travel and 1/4 travel. The optimal test pintravel is compressed to 1/3 of full stroke. Note: compress-ing the pins more than 1/4 travel shortens pin spring life.

Fixture with Press RodsTop view ofthe fixturewith thethreadedpress rodsinstalled andadjusted.

Installing Locking Nuts

One locking nut is installed on top of each threaded pressrod to lock it in place. I am using an electric screwdriverset to the lowest torque setting of 1 foot pound. The torqueis not critical, just do not use too much torque. The nylonparts will strip if over torqued. It doesn’t take much torqueto correctly and permanently lock the press rods in place.So, there is no need to overdue it.

Adjust Press Rods for 1/3 travel

Screw in the Press Rods

Locking Nuts

Press Rods







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Mechanically CompleteThe fixture is nowmechanicallycompletely cus-tomized to matchthe board undertest. The extranylon nuts shownhere are not neededsince this fixturewas tapped. Theextra nuts aresupplied for thosewho do not want totap the press plateand instead drilltheir press plateout to 1/4”. Theywill need to putthese nuts bothabove and below

Testing OperationTest the fixture forsmooth operation.Close the pressplate and makesure it latchesproperly and theboard under testslides smoothlydown the guidepins to contact thetest pins.

Opening Fixture

Open the fixture verify the circuit board raises withoutbinding. Verify operation is smooth. View from the sidesto make sure the circuit board remains level as it slides upand down the guide pins.

Complete

Open

Verify Alignment

the test plate to hold the press rods in place.







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Internal PartsI plan to put aribbon cableheader connector,terminal strip,and a combina-tion amplifier,controller, powersupply boardinside thisfixture. Thispicture showscentering andmarking the twoconnectors which will be mounted up inside underneaththe bed of nails plate. Your customizations will differdepending what you need to mount inside your fixture,if anything. The simplest way to make a fixture is towire all the pins to a back panel and then process all thesignals externally. I have a nice driver board that willfully drive this board under test. So in my case, it willmake a much more rugged and user friendly package tomount all of these delicate parts inside the fixture.

Setup For Drilling

Drilling Mounting Holes

Internal Parts Layout

Mounting Internal Parts

Drilling

Mounting Holes

Setup for drilling hardware mounting locations. Thispicture also shows how a fixture could be drilled withoutremoving the press plate.







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Using anelectricscrewdriverand a tappingblock to tapthe two 6-32holes for thetwo 1/2”standoffs.Thesestandoffsprovide amountingmethod forthe terminalblock.

Tapping Holes

CleanClean off drilllocation markswith IsopropylAlcohol.

Remove Bottom PanelRemove bottompanel to accessthe inside of thefixture

Set the Hardware in PlaceTemporarilyset thehardware inplace toprepare forwiring.

Tapping Small Holes

Clean

Remove Bottom Panel

Internal Hardware Mounting Locations







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The Technology of Wire WrappingA wire wrapped connection is made by coiling the wire aroundthe sharp corners of a terminal under mechanical tension. Thismethod of connection was fist developed by Bell TelephoneLaboratories, Western Electric Company.

METAL-TO-METAL CONTACTBy bending the wire around the sharpcorner of the terminal, the oxide layer onboth wire and terminal is crushed orsheared, and a clean, oxide-free metal-to-metal contact is obtained.

HIGH PRESSURE CONTACT

TRIPLE CONNECTION

EASY REMOVALA distinct advantage of wire wrapping is the ease with which awire may be removed from a terminal to correct errors or modifywiring. An unwrap tool is slipped over the terminal, engaging thefirst turn of the connection. Rotating the tool, the connection isremoved in seconds, without damage to the terminal.

TYPES OF WRAPA “Regular” bit wraps the bare wire around the terminal. A“Modified” bit wraps a portion of insulation around the terminalin addition to the barewire. This greatlyincreases the ability towithstand vibration.Modified wrap style is

STRENGTH OF CONNECTIONThe strength of a wire wrapped connection is considerably inexcess of that of a soldered one. It is less easily stripped from theterminal and is less subject to breakage.

GAS TIGHT CONTACT AREASThe contact areas of a wire wrapped connection remain gas tightwhen exposed to temperature changes, corrosive atmospheres,humidity and vibration.

Hints on Making Wrapped Connections

OVER PRESSUREDo not press too hard. Let the tools do the work.Excessive pressure can lead to over wrapping.

STAY WITH ITJust keep the tool on the terminal until thewrap is complete. Early removal can result inspiral and open wraps.

INSERT WIRE CORRECTLYBe sure to anchor the wire by wrapping back throughone of the two side slots. Be sure the stripped end ofthe wire is “pushed-in” all the way.

TOOL PULLINGDo not pull the tool. Let the tool do the lifting.Pulling the tool can lead to spiral wrapping.

USE THE CORRECT TOOLWire Wrapping is a precisiontechnique and the tool must fit thewire gage correctly. The wrongtool just cannot do the job. Improper selection can causeproblems ranging from “Pigtails” to loose wraps.

PROPER WIRE WRAP1. Strip 3/4” of insulation off of

the wire

2. Insert the wire all the way into theside hole of the wire wrap tool.

3. Anchor the wire by wrappingback through one of the two sideslots

4. Insert wire wrap tool over theterminal post of the receptacle.

5. The finished connection shouldlook as shown here.

recommended for a good durable bed of nails test fixture.







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Wire WrappingThesefixtures aretypicallywired usingwire wraptechniques.This isadequate formost applica-tions. In somecases highcurrentapplicationsmay requiresoldering alarger gage wire. In this example all connections will bedone using wire wrapping techniques.This page will quickly review wire wrapping. If you knowhow to wire wrap, you can skip this page.

Wire Wrap Tool

Shown above is the wire wrap tool. You simply strip about1/2” of insulation off of the end of the wire wrap wire andthen stick this wire into the offset hole on the tip of thewire wrap tool

Wrapping a PostNext place the center ofthe tool over a wrap postterminal and turn the tooluntil all the wire iswrapped tightly aroundthe post as shown here.

Connect the other end ofthe wire using the sameprocedure to make thewired connection asshown here.

UnwrapThe opposite side of the wirewrap tool unwraps the wirein case you make a mistake.

Wire Wrapping

Wire Wrap Tool

Wrap

Connection

Unwrap







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Plan and Mark Wire Routes

Planning and marking the planned wire routes with a finepoint marker helps make the job of wire wrapping turn outmuch neater.

Wipe Off Wire Rout Markings

Wire the fixture and then wipe markings off with IsopropylAlcohol.

Assemble Components

Shown above is the connector and terminal strip fullywired and mounted in place.

Full View of FixtureShows a full view ofthe inside of thefixture. The blank areain the back is wherethe controller boardwill be located. A flatcable will connectfrom the headerconnector to thecontroller board. Thecontroller board will becontrolled by RS-232via two 9pin D connec-tors mounted on therear panel of thefixture. The terminalstrip is used for customconfigurations in testing a various versions of the sameboard.

Mark Wire Routes

Wire, and Clean off Marks

Parts Wired and Mounted

Full View







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Adhere Rubber FeetAssemblebottom plateand adhere therubber feetsupplied withthe fixture kit.Use the 4holes in thebottom panelas guides forlocating therubber feet.Prior toadhering therubber feet,wipe off alloils and

CompletedFixtureCompleted bed ofnails test fixture readyfor production testing

Rubber Feet

Bottom View

Front View

Back View

contaminates withIsopropyl alchoholto allow the feet toadhere better.These holes mayalso be used toperminently mountthe fixture to atable top or astand.







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Other Internal Examples

Simple Test Fixture Wired to Rear Panel Connector

Complex

Heat Sinking Power Load Resistors

Perpendicular Board Mounting Saves Space

Internal Power Supply







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Supply List Finger Sensitive DrillThis handy attachment can convert your largedrilling, milling, and jig boring machine intoa slow-speed, finger-sensitive drill. Thisextra-sensitive adapter helps prevent rapiddrill dulling and breaking as well as drill“walking” and deflection. Fingertip controlallows you to feel the correct drilling pres-sure. Driller has a ball-bearing drill feedthat’s spring loaded. It automatically retractswhen the gripping ring is released. Driller has a #0JacobsT taper; hardened and ground ½” dia. shank (whichfits into a drill chuck or collet); and ¾” travel length.

Finger Drill #30 J0 Albrecht Keyless Chuck 0-1/8” (0-3 mm)Test Electronics..........TE-2823A1-3100A45

Self-Reversing Tapping ToolMove from forward tapping toreverse smoothly and quietly.Designed for manually-operateddrilling and milling machines,these attachments have a rollingball that provides a friction freetransition. Attachments reverse at1.75 times the forward speed for increasedproductivity. They’re self feeding to ensure gauge-perfectthreading. Torque-control clutch stops tap when it bottomsto prevent breakage.Cushioned drive eliminates cross threading and allows tapto pick up the lead of a previously tapped thread. Taps notincluded. Flexible collets are made of synthetic rubberbonded to hardened steel jaw inserts.

Tapping Tool 33 JT ....0-1/4” (1.6- 6.3mm)Test Electronics ...........TE-8317A65

Adjustable tools for mounting sockets at varying setheights. Available in inch or millimeter increments.TI-100 are for setting size 0.100” rated receptaclesTI-075 are for setting size 0.075” rated receptaclesTI-050 are for setting size 0.050” rated receptaclesThe “M” suffix designates millimeter dial increments.Test Electronics ...........TI-100Test Electronics ...........TI-075Test Electronics ...........TI-050

TE100 or TE100MTE075 or TE100MTE050 or TE100M

Wire Wrap WireKynar® Insulated Wire for WireWrapping is made with solid silver-plated, copper conductor, extrudedkynar (polyvinylidene fluoride)insulation. Extremely tough, high cut-through resistance. Self-extinguishing, will not support combustion. Excellent ultravioletand weathering resistance. UL rated at 105°C. Maximumtemperature rating: 135°. AWG 30. Nominal thickness: 0.005.Nominal OD: 0.02.Test Electronics ...........TE-4391430AWG

Wire Wrap ToolLow cost hand wire-wrapping, stripping, unwrapping tool forAWG 30 on standard .025” (0.63mm) square test pin postTest Electronics ...........TE-73365WWT

Receptacle Insertion Tools

Test Pin KitsQty 10 test pins and receptacles per kit.Part number specifies head style and size

Test Electronics ...........TP100-_ _ - _ _ _0451

04

51100075050head style

size center to center







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OEM ContactsDavid R. Lay, President, Chairman and CEODavid has been Chairman, President and Chief ExecutiveOfficer of Test Electronics, Inc. since October 1997. Priorto October 1997, he served as the President of the TestFixture Group since September 1990. From October[1986] until September 1990, Mr. Lay was Vice President,Finance and Chief Financial Officer of Test Electronics.

Mike Haskins, Sr. VP/Distribution UnitMike has been Senior Vice President, Distribution Unit ofTest Electronics, Inc. since September 2000 and VicePresident, Distribution from October 1997 until Septem-ber 2000. Prior to October 1997, Mr. Haskins served asVice President, Distribution of the Test Fixture Groupsince March 1993. He joined the Test Fixture Group in

Joe Fritz, Sr. VP/Test Fixture GroupJoe has been Senior Vice President, Test FixtureGroup ofTest Electronics, Inc. since September 2000. FromOctober 1997 until September 2000, he served as VicePresident and General Manager of the OEM business unitof Test Electronics, Inc. Prior to October 1997, Mr. Fritzserved as Vice President and General Manager of the

Dr. Luan A Hinkle, Sr. VP/Test Equipment GroupLuan has been Senior Vice President, Equipment Groupof Test Electronics, Inc. since September 2000. FromOctober 1997 until September 2000, she served as VicePresident and General Manger of the Industrial andScientific Test Equipment business unit of Test Electron-ics, Inc. Prior to October 1997, Dr. Hinkle served as VicePresident and General Manager of the Industrial and

Dr. Edward A. Armstrong Director ofEngineering /Test Fixture GroupEdward has been Director of Engineering, TestFixture Group of Test Electronics, Inc. since1986. Prior to 1986 Dr. Strohm was VPEngineering at Test Point 1 Fixture designgroup. Prior to that, he served on the faculties

OEM business unit for the Test FixtureGroup since January 1996. Hejoined the Test Fixture Group in July 1988 as Manufacturing Manager.

March 1992 as Vice President for European Distribution.

Matt P. Strohm, Sr. Design Engineer /Test FixtureGroupMatt has been Senior Design Engineer, Test FixtureGroup of Test Electronics, Inc. since August 1993.Prior to August 1993 he was VP Engineering at TestEng Inc. since 1986. Prior to 1986 Mr. Strohm was atest fixture design engineer at Genrad Inc.

Scientific Equipment business unit of the Test Equipment Group sinceApril 1995. She joined the Test Equipment Group in 1986 and advancedfrom fixture technician through a number of management positions to hercurrent position.

Charles V. Chandler, Sr. VP/Assembly EquipmentGroup Charles has been Senior Vice President, Assem-bly Equipment Group of Test Electronics, Inc. sinceSeptember 2000. From October 1997 until September2000, he served as Vice President and General Managerof the OEM business unit of Test Electronics, Inc. Prior toOctober 1997, Mr. Chandler served as Vice President andGeneral Manager of the OEM business unit for the Test

Brian Clevenger, Technical Writer /Test FixtureGroupBrian has been a Technical Writer, Test FixtureGroup of Test Electronics, Inc. since October 1997.Prior to October 1997, Brian served as GraphicArtist-Illustrator Test Fixture Group since March1993. He joined the Test Fixture Group in March1992 as an assistant publications technician.

Rodney Drumming, Machinist/Test Fixture GroupRodney has been a Machinist, Test Fixture Groupof Test Electronics, Inc. since 1993. Prior to1993, Rodney served as a machinist at SeagateTechnology Inc. Where he fabricated IR reflowpallets for flex circuit board assembly.

Martin Herrera, Machinist/Test Fixture GroupMartin has been a Machinist, Test Fixture Group ofTest Electronics, Inc. since September 1995. MartinJoined Test Electronics in 1991 as an entry levelmachinist. Prior to that he was an assistantmachinist at Walkins Johnson Inc.

About the Authors

Rudy Hoffman, Machine Shop SupervisorJourneyman Machinist /Test Fixture Group.Rudy has been a Machinist, Test Fixture Group ofTest Electronics, Inc. since 1990. Prior to 1990,Rudy served as a Journeyman Machinist at WalkinsJohnson Inc. Where he fabricated precision waferhandling equipment.

Fixture Group since January 1996. He joined the Test Fixture Group inJuly 1988 as Manufacturing Manager.

of Stanford University, Stanford Linear Accelerator Laboratories, HarvardUniversity and the Massachusetts Institute of Technology.

Email: [email protected]



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