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DVD-97CC TranscriptDVD-97CCPlated Through Hole RepairBelow is a copy of the narration for DVD-97CC. The contents forthis script were developed by a review group of industry experts andwere based on the best available knowledge at the time ofdevelopment. The narration may be helpful for translation andtechnical reference.Copyright © IPC – Association Connecting Electronics Industries. All Rights Reserved.The subject of this program is the replacement of a lifted (or missing) supported through holeland with no inner layer connections.A supported through hole is one in which the hole is plated or coated with a metal lining aroundthe inside of the drilled hole wall or barrel. Supported through hole lands sit at the top or bottomof these metal plated holes. The plating extends through the hole to the lands at the top andbottom, forming one continuous metal mass. The lands and the plating are connected in twoways.The first way the lands and the plating are connected is mechanically. This means that there is aphysical connection between the lands and the plating. The physical bond is strong enough towithstand the normal wear and tear of electronic products. The second way they are connected iselectrically. The lands and plating are parts of the same circuit.Anytime a land is torn away from the plating, the mechanical and electrical connections betweenthe land and the plating is damaged and should be restored. The method for restoring theseconnections, is to replace the old plating with a device called an eyelet. If you can see that theplating at the top, bottom or inside the hole is cracked or chipped, the original plating should beremoved and a replacement eyelet inserted. One exception to this rule is when a corner of a landis lifted and the plating inside the hole is undamaged. Assuming that the land can be reused, thelifted portion can be rebonded to the board surface using the dry film rebonding technique welearned earlier in this repair series.The eyelet insertion procedure can be used on single sided, double sided and multi-layer boards.However, unless you have special training, you should not use the eyelet insertion procedure oncertain types of plated through holes. As you know, multi-layer boards have two types of platedthrough holes: those with internal electrical connections and those with external electricalconnections or surface conductors only.1

DVD-97CC TranscriptAn inner layer connection is one where the connection to the plated through hole is made insideor below the surface of the board. Eyelet insertion on a plated through hole with internalelectrical connections is a complex procedure and is not described in this tape. We will onlycover the eyelet insertion procedure for plated through holes with external surface conductors.Let’s began the repair process with an analysis of the damage. When analyzing plated throughhole damage on multi layer boards, first check for inner layer electrical connections. The mostreliable method for discovering if there is an inner layer connection is to review the engineeringschematics (sometimes called the artwork) for that particular multi-layer board.Next, look for board damage and repair it if necessary. If the land is partially lifted, check to seeif the plating around the inside of the land is cracked, chipped or separated from the land. If theplating has been damaged, proceed with an eyelet replacement. Now, let’s begin the actual repairwork.We’ll start by cleaning the repair area. Then remove any contamination or solder masking ifnecessary and clean the area once again. Next we’ll select a replacement eyelet. Most eyeletscome from the manufacturer with a flat surface on one end, called a flange. We will call thisprefabricated flange the “factory flange. A technician makes the second “non-factory” flange byflaring and flattening the material that sticks through the other side of the hole after the eyelet hasbeen inserted.The selection of the replacement eyelet requires some simple math. To do the math you have tomake several measurements. We’ll explain what these measurements are right now. Allmeasurements can be made in the metric system of measure (centimeters, millimeters etc.) or inthe English system of measure (inches, feet etc.) For the purposes of this program we will use theEnglish system.The first measurement that must be made is the overall thickness of the board. Board thickness ismeasured in thousandths of an inch or “mils.” If a board is measured at 62 thousandths of an inchthick, you may hear the term, “the board is 62 mils thick.”Next, we’ll look at the Inside Diameter or ID of the replacement eyelet. The eyelet diametershould always be between three thousandths and twenty thousandths of an inch greater than thediameter of the component lead that will go through the eyelet. In other words the inside diameterof the eyelet must be bigger than the component lead but not too much bigger.Another critical measure is the Length Under the Flange, also called the LUF. This is the totallength of the eyelet minus the thickness of the factory flange. This length should be between 25and 35 thousandths longer than the thickness of the board. The protruding portion will beflattened or swaged to form the flange on that side of the board. In other words the inserted eyeletneeds to stick out of the board enough to create a flange.FD is Flange Diameter, or the width of the factory flange. The eyelet’s factory flange diametershould be slightly smaller than the land it sits on to provide for an acceptable solder fillet.Acceptable solder fillets are described in IPC’s publication A-610, Acceptability Of ElectronicAssemblies. This specific information can be found in the section on soldering.2

DVD-97CC TranscriptThe next measurement is called the Outside Diameter of the eyelet, or OD. The hole that theeyelet goes into can be between 1 and 5 thousandths larger than the eyelet’s outside diameter. Thehole should be big enough to allow the eyelet to be inserted without force, but small enough sothat the eyelet fits snugly: Not too tight, not too loose.Let’s review an example to show how a typical eyelet is selected. The first step is to measure thethickness of the board using a dial caliper or micrometer. Place the board between the jaws of thecaliper or the measuring faces of the micrometer and move the ends together until they lightlytouch either side of the board. Then check the reading. For the sake of our example, let’s say thatwe have measured a board, and it’s 62 thousandths, or 62 mils thick.Next, lets find the flange diameter measurement. To get this measurement locate one of the otherundamaged holes that the through hole component used. This is sometimes called a “sister” or“companion” hole. We’ll measure the diameter of the land above the companion hole. Thepreferred diameter of the factory flange on your replacement eyelet should be slightly smallerthan the companion hole’s land. It can’t be any smaller than the hole in the board or the eyeletwould fall out. It also can’t be so large that it interferes with the minimum spacing requirementsof nearby circuitry. For our example, the companion hole’s land measured 95 thousandths indiameter.Now we need to find the inside diameter of the replacement eyelet. As mentioned earlier, acorrect amount of space between the component lead and the eyelet wall is within the range of 3to 20 thousandths. The eyelet ID has to be large enough to leave space between the componentlead and the inside wall of the eyelet. This space will allow solder to wick up through the eyeletall the way to the top of the hole. However, if the space between the side of the lead and theinside wall of the eyelet is excessive, the molten solder won’t stay up in the barrel. It may justflow back out, or cause pits, voids or insufficient solder coverage.The typical method for a technician to measure the ID of the eyelet is to use a set of pin gauges tomeasure the inside diameter of a companion hole’s barrel. We know that the inside diameter ofour eyelet must be very close to, or the same size as, the inside diameter of the companion hole.Remember that the leads of the replacement component that will go in both holes are the samesize. So for the sake of our example lets say that the ID of the companion hole is fortythousandths.The next measurement we need to find is the OD or “outside diameter” of the eyelet. To find thismeasurement you must know the diameter of the hole that the replacement eyelet will fit into.The diameter of the hole will be the same size as the diameter of the drill bit or the ball mill youuse to ream out the hole. Remember that in order for the component lead to fit into the repairedhole, we must grind all of the damaged plating out of the hole. So we’ll select a ball mill or drillbit that is just slightly larger than the measurement of the companion hole’s diameter.3

DVD-97CC TranscriptThis slightly oversize mill or drill bit will grind out any remaining debris in the damaged hole.However, the bit or mill should not be so large that it digs into the board material behind theplating. The diameter size of a drill bit is stamped on the shank or the part that is inserted into thechuck of the drill motor, or on the drill bit holder. It’s always a good idea to double check thediameter of the bit or mill with your calipers. Ball mills come in sizes from #1 to #8. Eachnumber corresponds to a diameter size. For instance a #1 ball mill is 31 thousandths in diameter.A #5 is 63 thousandths.The outside diameter of the replacement eyelet must be 1 to 5 thousandths smaller than thereamed out hole. This will allow the eyelet to be inserted without force but not rattle aroundinside the hole. For this example, let’s say that we’ll use a #5 ball mill. A #5 ball mill is 63thousandths in diameter. To find this outside diameter of the eyelet range, we’ll take.063 andsubtract .001 and get 62 thousandths. Then take .063 and subtract .005 and get 58 thousandths.The range for the outside diameter of the replacement eyelet is between 62 and 58 thousandths ofan inch.Let’s continue with our example for selecting a replacement eyelet. The next measurement tomake is the length under the flange or LUF. The LUF needs to be 25 to 35 thousandths greaterthan the thickness of the board. This will give us enough extra material to make a proper secondflange. Remember that the board thickness was 62 mils or 62 thousandths. First , add .062 to .025to get 87 thousandths. Then add .062 to .035 to get ninety seven thousandths. We’ll select areplacement eyelet that is between eighty seven and ninety seven thousandths long under theflange.Now let’s look at a manufacturer’s eyelet chart to find our eyelet for this example. On themanufacturer’s eyelet chart, look under the LUF column to find an eyelet that is between eightyseven and ninety seven thousandths of an inch. Under the OD column, we’ll look for a numberthat falls within the range of sixty two to fifty eight thousandths, and select that particular eyelet.We’ll need to make sure that the ID of the replacement eyelet is the same or very close to thesame as the one you measured on the companion hole. In this case forty thousandths. Finally,let’s be sure to check that the replacement eyelet has a flange diameter that is small enough toavoid violating the spacing requirements of the surrounding circuitry. The diameter should beslightly smaller than a replacement land. In this example the flange diameter should be aboutninety thousandths.Occasionally the hole that needs to be repaired may be designated as the number one hole for apolarized component. Typically the land around number one holes are square or rectangular. Ourreplacement flange will need to have a shape that matches the shape of the original land. Tomodify the round shape of the factory flange, place the eyelet on a hard metal surface and hold itin place, or place it in a jewelers anvil. Then, using a knife blade or chisel, trim the edge of it tocreate the shape of the number one hole.Now we’re almost ready to insert the eyelet we selected into the hole we have cleaned out. Butbefore we do, we need to prepare the lands and any attached conductor material that the eyeletflanges will sit on. First replace all lands and conductors that are missing or badly damaged.4

DVD-97CC TranscriptThen, tin the lands if they are not pre-tinned. If you do have to tin a land be sure that the coatingof solder is very thin. Be sure to remove any excess solder. We don’t want the flange to sit abovethe board on a thick layer of solder. If excess solder lifts the flange up off the surface of theboard, the length of the eyelet that extends out through the other side of the hole would bereduced. We would have a hard time creating the second flange because we wouldn’t haveenough eyelet material to work with. Now, after the tinning, let’s clean away any solder fluxresidue before the eyelet is inserted.The next step is to insert the eyelet. Whether the factory flange is on the component ortermination side of the board will depends upon the situation. The eyelet is typically inserted upfrom the bottom or termination side of the board. In other words, the factory flange is usually onthe bottom of the board, with the other end of the eyelet on the component side. But, if thereplacement eyelet needs to be the number one hole, as mentioned earlier, you have to nip theedges of the flange to form a square shape. In this case the factory flange would be on thecomponent side rather than on the termination side of the board. If you have inserted the eyeletinto the termination side of the hole, it may want to slip out. A piece of heat resistant tape willhold the eyelet in the hole while you work with it.Next, we’ll flatten or “swage” the portion of the eyelet that extends through the board. The eyeletcan be either partially swaged which is called a “funnel set” or it can be fully swaged which iscalled a “flat set.” Most technicians in the field swage the second flange by hand. Severalmanufacturers make the necessary hand tools, but they all have similar parts and work in thesame manner. Each manufacturer provides an upper setting tool and a lower support tool.You will probably have to suspend the board in a board holder above the lower support tool.Place the factory flange on the flat surface of the lower support tool. Then, place the cone shapedtip of the upper setting tool into the unformed end of the eyelet. Now, push down firmly on theupper setting tool. For a funnel set flange, the cone shape of the end of the upper tool is machinedto create the proper funnel angle.If you want to make a flat set flange, tilt the handle slightly as you push down and began to rotatearound the eyelet to increase the width of the funnel shape. Start with small rotations and getlarger as you continue to widen the funnel. Stop when the funnel shape is approximately on a45% angle with the surface of the board. The angle must start at the surface of the board. Now,reverse the tip in the handle of the upper setting tool. Then press the eyelet flange flat. Adescription of acceptable flange settings can be found in the IPC - A - 610 publication in sections2.3.1 - 2.3.2.After the eyelet has been swaged, we’ll need to solder the top flange to the land. The solder mustform a filet or joint that extends completely around the flange for 360 degrees. This solderingprocess can also be accomplished during the installation of the replacement component. Thismight be better, since it would eliminate one heating cycle in the repair process. Excessive heatbreaks down the land’s bonding material and can damage the laminate material. If you do solderthe flange to the land at this stage, be sure to clean away the solder flux with the appropriatecleaning solvent.5

DVD-97CC TranscriptAs mentioned before, some companies allow the factory flange of a replacement eyelet to be usedas a replacement land. If the original land was connected to a surface conductor, that conductoror its replacement must be re-connected to the eyelet flange that is now being used as a land.Before you insert the eyelet, lap solder a replacement piece of foil jumper onto the originalconductor, at a point where the original conductor is still firmly bonded to the board. Then, runthe new conductor material to the hole and let it extend down into the hole slightly. Then cleanthe conductor. Now, insert the eyelet into the hole allowing the factory flange to pin the foiljumper in place. Next, we’ll solder the replacement conductor to the eyelet flange and clean thearea thoroughly.Then, overbond the replacement conductor and cure the overbond epoxy according to the epoxymanufacturers instructions. Be sure to keep the overbond epoxy off the land and out of thethrough hole.The last step is to evaluate your work. First, lets check that the land and its conductor have securephysical bonds to the board. Make sure that the land or flange diameter does not violate minimumconductor spacing requirements.6