Pinball Rehab

pinball repair and restoration

Repairing Plated Through-Holes Repairing Plated Through-Holes Hot video

It is not uncommon to find damaged plated through-holes when repairing a pinball circuit board.  There are two techniques commonly used to repair this type of damage: solder stitch or eyelets.  First we'll look at analyzing the damage and then review the repair options.

Analyzing the Damage

Image 1 provides a side view of the plated through-hole. The through-hole is actually one physical part and the board trace a second physical part.  They are electrically connected once the board is wave-soldered.  It is fairly common for the connection to break right at the point where the through-hole is soldered to the board trace.  It is also common to find the traces on the top and bottom still intact, but the metal liner in the hole gone.

We need to perform two connectivity tests in order to determine the exact damage.

Set your DMM on continuity and test each through-hole by putting one lead on the oval pad on the top side of the board and the other on the oval pad on the bottom side of the board.  Do not put the leads into the hole or you'll just touch them together.  This test will check the condition of the through-hole.

Next follow the board trace for each through-hole until it connects to a component and check the continuity between there and the through-hole, or the oval pad.  The trace may continue either on the top or the bottom of the board, so check both sides.  You can also use a probe with a sharp point to gently press through the green coating on the trace and then check continuity.

Image Gallery

Repairing Plated Through-Holes
Repairing Plated Through-Holes
Repairing Plated Through-Holes
Repairing Plated Through-Holes
Repairing Plated Through-Holes
Repairing Plated Through-Holes
Repairing Plated Through-Holes
Repairing Plated Through-Holes
Repairing Plated Through-Holes
Repairing Plated Through-Holes
Repairing Plated Through-Holes
Repairing Plated Through-Holes
Repairing Plated Through-Holes
Repairing Plated Through-Holes

In my case I didn't find anything that I hadn't already identified with a visual check.  Although this is not always the case, so it's best to confirm your observations with a DMM.

In Image 2, about half of the far left through-hole pad is missing and there is no connectivity between the two sides of the board.  In Image 3 the entire pad (fifth hole from the left) is missing in action and again there is no connectivity between the two sides. So now that we've identified what repairs are needed, on to the fun stuff.

Solder Stitch

Twenty years ago this was the most commonly taught method for repairing damaged through-holes.  Today there are better, more professional looking, solutions, but for the sake of thoroughness I will cover this method also.

You will need some 3/4 inch long strands of 16-22 gauge wire (depending on the size of the through-hole).   Clean the hole out using an appropriately sized drill bit (do not use a power drill, do it by hand).  Clean the oval traces (both sides) with a fine grit sandpaper or a fiberglass pen and wipe down with alcohol.  Insert three of four of the wire strands through the hole, fold over on each side and trim.

If earlier we had found any cracks where the oval pad connects to the board trace we would leave our wires slightly longer (on the top or bottom as needed) and then bend them over and solder to the board trace.  Don't forget to scrape off the green solder mask on the trace where you are soldering.

Apply solder to one side and ensure the solder flows through to the other side (do not fill the hole since we still have to install our component).  I usually insert a toothpick in the hole to help align the strands before soldering.  The strands on each side should have a solid connection to the pad (or trace as mentioned above).  At this point you can install your connector, socket or component and complete the soldering.

Eyelet Method

The best way to repair through-hole damage is with eyelets, and this is the method anyone charging for board repair should be using. 

Installing the eyelets requires a staking tool, which clinches down the eyelet, an anvil, which supports the bottom side of the eyelet, and an eyelet press (see Image 4; staking tool on the top-right and anvil on the bottom-right).  The eyelet is placed in the damaged through-hole and then crimped similar to the way a hollow rivet is installed in a ramp flap.

While the eyelets only cost about ten cents, the eyelet press runs about $1,300 and the staking tool and spring-loaded anvil will cost between $90 and $500.  Plus you need a staking tool and anvil for each size eyelet.  Thankfully, there are a couple of cheaper options. 

Best Electronics Soldering Technologies sells a plated through-hole repair kit, which costs about $200.  The kit includes several sizes of setting tools and a basic anvil (non-spring-loaded), which are used with a hammer to clinch the eyelet.  Although you can put together your own kit for a lot less with the following products.

Mouser carries the Keystone line of eyelets and Keystone setting tools.  The most common eyelets you'll need are 1/16" diameter for most IC's, 3/32" for transistors and 1/8" for large connectors.  The best lengths to get are .093" or .125".  I think the .093" is perfect, but some prefer the .125" and then file it down a little bit, and trim the diameter, when needed.

Note: There are other brands of eyelets that have a lower profile on the eyelet flange, which means they don't spread as much.  I will probably give one of the other products a try next time I order some eyelets.

The Keystone 1714 staking tool is used with 1/16" to 3/32" diameter eyelets and the 1715 is used with 1/8" eyelets.  Each costs about ten dollars. 

You can buy a setting tool (staking tool on one side and anvil on the other) and tool base, which holds the anvil, at Circuit Medic.  The setting tool (115-3120) costs $17 and the tool base (115-3122) costs $10.  This is not as good a setting tool as the Mouser options since it does not roll-over the edge of the eyelet, so just use the anvil side of the tool.

So for a grand total of $47 (plus some drill bits and a small hammer) you can do a professional eyelet repair.

Although I don't think the spring-loaded anvil is necessary, you can buy them at the Engineering Lab for $89.  You could also use a cupped tip punch as the anvil, but the setting tool from Circuit Medic works better.

Rather than use a hammer you could mount the staking tool and anvil in a drill or bench press.  It doesn't take a lot of pressure so even the drill press works fine.

Eyelet Selection Criteria

  • The eyelet inside diameter should be a .075 - .500 mm (.003"-.020") greater than the component lead diameter.
  • The length of the eyelet barrel should be .630 - .890 mm (.025" - 035") greater than the thickness of the circuit board.
  • The eyelet flange diameter should be small enough to prevent interference with adjacent lands or circuits.
  • The clearance hole drilled through the circuit board should allow the eyelet to be inserted without force but should not exceed .125 mm (.005") greater than the eyelet outside diameter.

Eyelet Example 1

In Image 5 you can see damage done to multiple through-holes by someone who clearly should not have been soldering.  We'll start by fixing the circled through-hole using the eyelet method.  In addition the trace going to the right has been lifted and the trace going to the left is barely hanging on.

First decide which eyelet you will be using and then use a drill bit of the same size to clean out any remaining barrel on the damaged through-hole.  Do this by hand rather than with a power drill.

Image 6 shows the front of the board and Image 7 the back after cleaning the hole with a 1/16" drill bit (use the appropriate sized bit based on the through-hole size).  Part of the through-hole was still attached on the back side and fell off after cleaning the hole.  This will often happen if there are no traces going to one side of the through-hole.

Be careful not to lift or damage any existing traces.  When cleaning out the hole work from the side where the traces are in order to minimize the chance of damage.

Before installing the eyelet remove the solder mask from any traces you will be overlapping and lightly tin the trace (remove any excess using solder wick).  In Image 8 you can see the eyelet in place.  Always place the flange end of the eyelet on the backside of the board (the side without components).

Note: I was focused on taking pictures, instead of thinking, and put the eyelet in backwards (the flange is on the component side).  See Example 2 for the correct installation.

Make sure the flange on the eyelet doesn't interfere with other traces, through-holes or pads.  Be aware it will expand when you set it. 

If you're doing two or more through-holes right next to each other the flanges will most likely end up touching.  In this case, I file two flat sides on the flange, turning the circle into an oval, before installing the eyelet.  Easiest method is to insert the non-flange end of the eyelet in a straight, round solder pick and then hold the flange in place with your fingernail while running it across a file.

I epoxied the left trace, which is now pressed under the eyelet.  The right trace was still short of reaching the eyelet so a jumper will be necessary.

All I had on hand at the moment was a .125" eyelet and as you can see in Image 9 it's a little long.  You want about 1/32-1/16" extending beyond the beyond the board.  I used a file to remove about half of the part that was extending beyond the board.  If the flange is too long you risk interfering with other traces when you roll it over.

Always use a very small hammer when cinching the eyelet to prevent damaging the board.  It does not take much pressure to clinch the eyelet and you are less likely to split the eyelet if you use multiple light taps.

Place the side of the eyelet with the flange on the anvil.  Before using the staking tool you can use a center punch to start rolling the edge of the eyelet (this helps prevent splitting the eyelet as we roll the flange).  Take the punch and place it in the non-flanged side of the eyelet while holding it at slightly more than a 45 degree angle from the board.  Then rotate the punch around the edge of the eyelet which will begin to fold it over and prevent cracking as we proceed.

Now while holding the board on the anvil, put the staking tool in place and give it a few light taps.  With the setup I previously described I find it works best to do about 6 taps on one side and then reverse the setup and do about 6 more taps.

When you're done make sure the eyelet is tight against the board and won't rotate.  Check for continuity between the eyelet and the trace.  If the eyelet is not cinched properly you will have problems.  Give it a few more taps if that's the case.

Inspect for any areas where either side of the eyelet may have spread and is touching another eyelet, pad or trace.  If necessary you can trim the eyelet with an X-acto knife or Dremel tool with a cut-off blade.  Just be careful not to damage any other traces  (this is why I usually trim the flange in advance when working in tight spaces).

In Image 10 you can see the finished product.  Sorry about the blurry picture.

At this point you need to solder any traces to the eyelet or solder the eyelet to any remaining portion of the pad.  In my case just the left trace needed solder, since I will be adding a jumper to the right trace before installing the socket.

Make sure not to get any solder in the eyelet hole.  If you get too much solder on the joint just use some solder wick to remove the excess.

Normally I'm not a big fan of sockets, but that same chip could fail in the future.  If that happens and we've installed eyelets and jumpered traces the repair will be a lot more difficult the second time.  So consider installing a socket as paying it forward.

The video at the end of the article shows a fairly similar approach to installing eyelets.

Eyelet Example 2

In Image 11 the eyelets have already been set for pins 10, 16, 17 and 18 and the holes drilled for pins 10-14 (pin one is at the bottom right and then count counter-clockwise).  Several jumpers will also be required since the breaks in the trace are too far away for the eyelet to cover them.

You can see one jumper already partially in place for pin 10.  It will be inserted into the through-hole before installing the socket.  I will also be installing jumpers on pins 11 and 13. 

In Image 12 the rest of the eyelets and jumpers are installed.

In Image 13 you can see the bottom of the board with the eyelets installed.  Note that a couple of the eyelets that I did not file before installation are touching and will have to be cleaned up with an X-Acto or Dremel with a cut-off wheel.  While this problem is more prevalent on the flange side of the eyelet, it can also happen on the component side.

If you are having trouble with the eyelets touching on the component side, just slightly file down the length of the eyelet after installation and before setting.

In Image 14 the socket and IC have been installed.  Once cleaned up and a green protective coating applied over the bare traces, the repair will hardly be noticeable.