Annular Ring and Through-Hole Pad Repair

Section Overview

The pads repaired so far sat flat on the surface; this advanced section takes on the through-hole pad, which is really two connected features and so has two things that can fail. A through-hole pad has an annular ring — the ring of surface copper around a drilled hole, on one or both faces of the board — joined through the board by a barrel — the thin plated-copper wall lining the hole that carries the connection from one side to the other (§2.2). A component lead passes through the hole and solders to the ring, and the barrel ties the two faces together. Either part can be damaged. The ring can tear or break — pulled off with a stubborn component or over-stressed — and is repaired much as any pad, by rebuilding it from copper and reconnecting it to its trace (§6.2). The barrel is the harder case: its plating can crack or be destroyed, as when a seized lead is drilled out, breaking the connection through the board. When the barrel is gone, the connection is restored mechanically: an eyelet — a small hollow metal rivet — is fitted into the hole and set by swaging — flaring its ends against the ring on each side to bridge the two faces and grip the board, standing in for the lost plating. A simpler alternative, where it suffices, is a wire passed through the hole and soldered to the ring on both sides, joining the faces directly (§5.4). Deep or full barrel re-plating belongs to via repair (Chapter 7). This section walks the anatomy, the failure modes, rebuilding a ring, restoring the through-connection by eyelet or wire, and fitting the lead and verifying both sides. Learn the ring and the barrel, and the through-hole pad — the most structured pad on the board — becomes repairable.

Why This Matters

A through-hole pad carries a connection through the board as well as on its surface, so repairing one means restoring both the ring and, when it is damaged, the connection through the hole — and getting either wrong leaves the joint half-made. This matters because the ring and the barrel are separate failures: a torn ring and a destroyed barrel need different repairs, so recognizing which has failed — or that both have — is the first step (§2.2). This matters because the through-connection is easy to overlook: a rebuilt ring that looks perfect on top can still be open through the board if its barrel is gone, so the connection between the faces must be checked and, if broken, deliberately restored (§5.6). It matters because the barrel joined two sides and often an inner layer: losing it can break a net that a surface repair alone cannot reach, which is why an eyelet or a through-wire is needed to rejoin the faces. It matters because a component lead must still fit and hold: the repair has to leave a hole the lead passes through and a ring it can solder to on both sides, so the repair serves the part, not just the copper. And it matters because some barrel damage is beyond a hand eyelet: deep plating loss inside a multi-layer board is via-repair territory, and knowing that boundary keeps you from a repair that cannot hold (Chapter 7; §4.5). Repair the ring and the barrel both, and a through-hole pad is whole again on both faces and through the board.

Required Prerequisites

• Rebuilding a Destroyed Pad — Section 6.2 taught rebuilding a pad from fresh copper, which is exactly how a broken annular ring is restored.
• Via Types: Through-Hole, Blind, Buried, Micro — Section 2.2 covered plated holes and how a barrel connects the layers, the anatomy this repair works on. The wire link (§5.4) is also used for the through-connection. This is an advanced hands-on hot-work repair section — read the Safety Notes before starting.

Recommended Consumables

• Repair eyelets or via rivets in the hole sizes you meet, and a setting tool — the parts and means to restore a through-connection (§2.2)
• Copper foil or a pad-repair kit, and high-temperature adhesive — to rebuild a broken annular ring (§6.2)
• Flux, fine solder, and fine magnet wire — to solder both faces and to make a through-wire connection (§5.4)
• A solder mask pen and isopropyl alcohol — to clean and reseal the finished repair (§6.2)
• Scrap through-hole boards with damaged rings and holes — to practise on; do NOT practise on any device you intend to use, sell, or return

Recommended Practice Hardware

• A temperature-controlled soldering iron with a fine tip — to solder the ring on both faces at controlled heat (§5.3)
• A small reamer or drill matched to the hole — to clean a hole out to sound copper or to take an eyelet
• An eyelet setting (swaging) tool — to flare and set a repair eyelet squarely
• A magnifier or loupe and a bright light — to inspect the ring, the hole, and both faces
• A multimeter with continuity and a low-ohms range — to verify the connection ring-to-ring and to each trace (§5.6)
• Good ventilation — to keep solder and flux fumes out of your breathing air

Real-World Applications

Through-hole pad repair is the skill that saves boards where a lead has torn a ring or destroyed a plated hole, common on older and heavily-reworked equipment. A technician who lifts an annular ring pulling a seized resistor rebuilds the ring from copper and reconnects it to its trace (§6.2). Someone who has drilled out a stubborn lead and destroyed the barrel fits an eyelet and sets it by swaging to restore the connection through the board. A repairer on a double-sided board with a lost plated hole passes a wire through the hole and solders it to the ring on both faces, rejoining the sides (§5.4). A technician facing deep barrel damage inside a multi-layer board recognizes it as via-repair work and does not force an eyelet that cannot reach the inner connection (Chapter 7). And a repairer finishing a through-hole repair checks continuity ring-to-ring and to both traces before refitting the component (§5.6). The failures this skill prevents: leaving a rebuilt ring open through the board, forcing an eyelet where deep re-plating is needed, and returning a through-hole joint sound on one face but broken on the other.

Common Challenges

• Missing the broken barrel. A perfect-looking ring can still be open through the board — check continuity face-to-face and restore the barrel with an eyelet or wire if it is gone (§5.6).
• Forcing an eyelet where re-plating is needed. Deep barrel loss in a multi-layer board is via-repair work — do not trust an eyelet that cannot reach an inner-layer connection (Chapter 7).
• A skewed or loose eyelet. A badly-set eyelet grips or contacts poorly — ream the hole clean and set it squarely by swaging.

Safety Notes

Risk Level: Medium. This repair adds reaming or drilling and eyelet-setting to the usual soldering, so mechanical hazards join the hot-work ones.

Professional Tips Before Starting

• Test through the board first. Check continuity face-to-face before you start, so you know whether the barrel is intact or must be restored — the through-connection is the part most often missed (§5.6).
• Match the eyelet to the hole. Ream the hole clean and size the eyelet to it before setting — a rivet that is loose or forced will not contact well.
• Keep the lead in mind. Leave a hole the component lead still passes through and a ring it can solder to on both faces — the repair has to take the part (§2.2).

Repairing the Ring and the Hole

Recap and Frame

The last two sections repaired surface pads; this one adds the dimension a through-hole pad has that a surface pad does not — a connection through the board (§6.1; §6.2). The frame to hold is that a through-hole pad is two features in one: an annular ring of surface copper around the hole, on one or both faces, and a barrel of plated copper lining the hole that joins those faces (and often inner layers) together (§2.2). A component lead runs through the hole, solders to the ring on each side, and relies on the barrel to tie the faces electrically. Because there are two features, there are two repairs, and a full fix may need both. If only the ring is damaged, you rebuild it as a pad and reconnect its trace — familiar work (§6.2). If the barrel is destroyed, you must restore the connection through the hole by other means, because the plating that carried it is gone. Two methods do that: an eyelet set by swaging, which puts a metal rivet through the hole to bridge and grip both faces, and a wire through the hole soldered to both rings, which joins them directly (§5.4). The one thing you cannot do by hand is re-plate a barrel deep inside a multi-layer board — that is via repair (Chapter 7). So this section walks the anatomy, how each part fails, rebuilding the ring, restoring the through-connection, and fitting the lead and verifying both faces. Hold the frame — ring and barrel, two features and two repairs — and the through-hole pad stops being intimidating.

Anatomy: The Ring, the Barrel, and the Hole

Repairing a through-hole pad starts with seeing its three parts clearly, because each plays a different role and fails in a different way. The annular ring is the surface copper: the ring-shaped pad around the drilled hole, present on the top face, the bottom face, or both, to which the component lead solders and to which the trace connects (§2.3). The barrel is the through-connection: a thin tube of plated copper lining the wall of the hole, formed when the board was made, that carries current from the ring on one face to the ring on the other — and, on a multi-layer board, to the inner layers the hole passes (§2.2). The hole itself is the space the component lead passes through and that the barrel lines. Together they make a plated-through hole: lead through hole, soldered to ring, tied face-to-face by barrel. Seeing the three parts tells you what a given damage has cost. A torn ring loses the surface pad and its trace connection but may leave the barrel intact. A destroyed barrel loses the through-connection but may leave both rings whole. And losing both — a ring pulled off and the barrel drilled out with it — needs the ring rebuilt and the through-connection restored together. A backlight and a meter help you read them: look at both faces for the rings, and measure face-to-face through the hole to test the barrel (§5.6). Know the ring, the barrel, and the hole, and any through-hole damage resolves into which parts must be repaired.

How Through-Hole Pads Fail

Through-hole pads fail at the ring, at the barrel, or at both, and each has its own causes worth recognizing before you repair. The ring fails much as any pad. It tears or lifts when a component is pried, yanked, or desoldered carelessly — a lead that will not release can peel its ring off the board — and it can crack from over-stress or corrode away (§6.1). A ring is a surface feature, so its damage is visible, and it is repaired as a pad. The barrel fails less visibly and often more seriously. Its commonest destroyer is drilling out a seized lead: when a component lead is soldered so stubbornly it will not desolder, drilling it free can tear out the thin plating with it, leaving a bare hole and no through-connection. Heat and corrosion take barrels too: repeated reworking can crack the plating, and moisture can corrode it through. The barrel's failure hides because the rings can look perfect while the connection between them is open, which is why a face-to-face continuity check is essential (§5.6). A special case is the inner-layer barrel: on a multi-layer board the barrel also connects inner layers, so destroying it can break a connection that no surface repair reaches, pushing the job toward via repair (Chapter 7; §2.5). Reading the failure — ring, barrel, or both, and how deep — tells you the repair: a rebuilt ring for surface damage, an eyelet or wire for a lost barrel, and via repair for deep inner-layer plating loss. Diagnose which part failed, and the right repair follows.

Repairing a Broken Annular Ring

A broken or torn annular ring is repaired as a pad, because that is what it is — a ring of surface copper around a hole — so the pad-repair skills carry straight over (§6.2). Assess and clear first: judge whether the ring is merely lifted (re-adhere it) or torn and lost (rebuild it), and clear any destroyed copper and cratered laminate back to sound board around the hole (§6.1). Rebuild the ring from copper: cut a ring or pad from copper foil to fit around the hole, or use a pre-formed ring from a pad-repair kit sized to the pad, leaving the hole open for the lead (§6.2). Bond it down with a high-temperature adhesive, pressed flat and fully cured, keeping the hole clear and the solderable face clean (§6.2). Reconnect it to its trace: join the rebuilt ring to the trace it served with a short solder bridge or a fine wire link, exactly as for a surface pad (§5.4). Mind the hole through it all: the ring must keep a clear hole the component lead passes through, so do not let copper or adhesive block it, and ream it gently clear if it does. And remember the other face: if the pad is double-sided, the ring on each face may need its own attention, and the two are tied by the barrel — or, if the barrel is gone, by the through-connection you will restore next. A ring rebuilt from copper, bonded, reconnected to its trace, and left with a clear hole is a repaired annular ring — ready for its through-connection and its lead. Rebuild the ring as a pad, and half the through-hole repair is done.

Restoring the Through-Hole Connection

When the barrel is destroyed, the connection through the board is gone and must be remade, and two hand methods do it: an eyelet, or a wire through the hole. The eyelet is the purpose-made repair. An eyelet — a small hollow metal rivet, also sold as a via rivet — is chosen to fit the hole, slipped through it, and set by swaging: a setting tool flares its ends outward against the ring on each face, so the rivet grips the board mechanically and contacts both rings electrically, standing in for the lost plating (§2.2). Ream the hole to clean copper and to the eyelet's size first, set the eyelet squarely so it seats flat on both faces, and then solder each flared end to its ring, which both secures it and completes the electrical joint. The wire-through-hole method is the simpler alternative. Where an eyelet is not to hand or the hole is awkward, a short length of wire is passed through the hole and soldered to the ring on both faces, joining the two sides directly, much like a tiny two-sided wire link (§5.4). It restores the surface-to-surface connection well, though unlike an eyelet or plating it does not line the whole barrel, so it suits double-sided boards more than deep multi-layer ones. Know the boundary: neither method re-plates a barrel deep inside a multi-layer board or restores a broken inner-layer connection — that is via repair, and forcing an eyelet to do it leaves an unreliable joint (Chapter 7). Choose the eyelet for a clean, durable through-connection and the wire where it suffices, and the barrel's job is done again. Restore the through-connection deliberately, and the pad conducts from face to face once more.

Fitting the Lead and Verifying Both Sides

A through-hole repair is finished only when the component lead fits and the connection is verified on both faces and through the board — more checks than a surface pad because there is more to a through-hole pad (§5.6). Fit the lead first: confirm the component lead still passes through the hole and seats, reaming gently if an eyelet or solder has narrowed it, then solder the lead to the ring on each face it reaches, making a sound joint on both sides (§5.3). Verify the through-connection: measure continuity ring-to-ring through the hole, confirming the barrel — whether restored by eyelet or wire — actually carries the connection from face to face, near the resistance of a known-good joint (§5.6). Verify each ring to its trace: confirm each face's ring connects to the trace it should, so the pad is joined into the circuit on every layer it serves (§5.4). Check for shorts: confirm the eyelet or wire touches only its own rings and not a neighbour. Verify mechanically: the eyelet should be tight and the rings bonded, so nudge the lead and the rings gently — nothing should shift (§6.2). Then protect it: reseal the rings and bare copper on both faces with a solder mask pen (§6.2). A through-hole pad that carries continuity ring-to-ring and to each trace, holds the lead firmly, and is sealed on both faces is a finished repair; one open through the board, or on one face, is not — restore what is missing and re-verify (§4.5). Verify both faces and through the hole, and the through-hole pad is whole in every direction it must connect.

Common Mistakes

• Fixing the ring but not the barrel. A rebuilt ring can still be open through the board — check face-to-face continuity and restore the barrel with an eyelet or wire (§5.6).
• Blocking the hole. Copper, adhesive, or solder can close the hole the lead needs — keep the hole clear and ream it gently if it narrows.
• Forcing an eyelet on deep damage. An eyelet cannot re-plate an inner-layer barrel — treat deep barrel loss as via repair (Chapter 7).
• Setting an eyelet crooked. A skewed eyelet contacts and grips poorly — ream clean and set it squarely by swaging.
• Verifying only one face. A joint sound on top can be open underneath — verify the ring, the trace, and the through-connection on both sides (§5.6).

Troubleshooting Guidance

Through-hole pad problems come down to a ring, a barrel, or a lead that is not right. If a rebuilt ring is open to its trace: the trace connection is missing — bridge it with solder or a wire (§5.4). If the rings are fine but open face-to-face: the barrel is gone — restore it with an eyelet set by swaging or a wire through the hole (§5.6). If an eyelet contacts poorly: it is loose or skewed — ream the hole and reset it squarely. If the lead will not pass through: the hole is narrowed by solder or an eyelet — ream it gently to size. If the connection is open on an inner layer: the damage is beyond a hand eyelet — it is via repair (Chapter 7). If a face-to-face short appears: the eyelet or wire is bridging a neighbour — clear and insulate it (§5.4). If the ring lifts while soldering: you are overheating — work cooler and faster and heat-sink (§4.3). If you cannot restore or verify the through-connection: the board may be beyond hand repair — refer or replace (§4.5). The throughline: rebuild the ring, restore the barrel by eyelet or wire, fit the lead, and verify both faces and through the hole.

Verification & Testing Methods

Confirm the repair on both faces and through the board before trusting it:

• [ ] I rebuilt any broken annular ring from copper and reconnected it to its trace, keeping the hole clear (§6.2).
• [ ] I restored a lost through-connection with an eyelet set by swaging, or a wire through the hole, so the barrel's job is done (§5.4).
• [ ] I verified continuity ring-to-ring through the hole and each ring to its trace, near a known-good value (§5.6).
• [ ] I fitted and soldered the component lead on both faces and confirmed no short to a neighbour (§5.3).
• [ ] I tested the eyelet and rings mechanically with a gentle nudge and resealed both faces with a solder mask pen.

Then try the practice exercises below — hands-on repair practice on scrap boards; scenarios differ from the quiz.

Practice Exercises

1. Read the anatomy (5 minutes, reasoning). On a scrap through-hole board, identify the annular ring on each face, the hole, and, with the meter, test whether the barrel still carries the connection face-to-face (§5.6).
2. Rebuild a ring (7 minutes, hands-on). Rebuild a torn annular ring from copper foil or a kit around the hole, bond it, keep the hole clear, and reconnect it to its trace (§6.2).
3. Set an eyelet (8 minutes, hands-on). Ream a hole with a lost barrel to size, fit an eyelet, set it by swaging, and solder each end to its ring.
4. Verify both sides (5 minutes, hands-on). Fit a lead, measure continuity ring-to-ring and to each trace, and nudge to confirm the eyelet and rings hold (§5.6).

These core ideas — the ring, barrel, and hole, how each fails, rebuilding a ring, restoring the through-connection by eyelet or wire, and verifying both faces — are tested in the Chapter Quiz at the end of this chapter, where a score of 80% is required to continue.

Key Takeaways

• A through-hole pad is two features: an annular ring of surface copper on one or both faces, and a barrel of plated copper through the hole joining them — either can fail and a full repair may need both (§2.2).
• A broken annular ring is rebuilt as a pad — cut from copper, bonded, and reconnected to its trace — while keeping the hole clear for the lead (§6.2).
• A destroyed barrel is restored with an eyelet (a hollow rivet) set by swaging to grip and bridge both faces, or a wire through the hole soldered to both rings (§5.4).
• Deep barrel or inner-layer plating loss is not a hand-eyelet job but via repair, and forcing an eyelet there leaves an unreliable joint (Chapter 7; §4.5).
• Verify a through-hole repair on both faces and through the board: continuity ring-to-ring and each ring to its trace near a known-good value, the lead fitting and held, and no short (§5.6).

Skills Learned

• You can now identify the annular ring, barrel, and hole of a through-hole pad.
• You can now recognize ring and barrel failures on a through-hole pad.
• You can now rebuild a broken annular ring from copper.
• You can now restore a through-hole connection with an eyelet set by swaging.
• You can now restore a connection with a wire through the hole where suitable.
• You can now fit the lead and verify the repair on both sides of the board.

Glossary Additions

• barrel — the thin tube of plated copper lining the wall of a drilled hole in a board, formed when the board is made, that carries the electrical connection from the pad or annular ring on one face through to the ring on the other, and on a multi-layer board to the inner layers the hole passes. The barrel is what makes a plated-through hole a connection rather than just a hole, and when its plating cracks, corrodes, or is torn out — often by drilling out a seized lead — the through-connection is lost even if the surface rings remain whole. A destroyed barrel is restored by hand with an eyelet or a wire through the hole, while deep or inner-layer barrel loss is the province of via repair.
• eyelet — a small hollow metal rivet fitted into a drilled hole and set in place to restore the through-board connection of a plated hole whose barrel has been destroyed; it is also sold as a via rivet. Chosen to match the hole, the eyelet is slipped through and set by swaging, which flares its ends against the annular ring on each face so it grips the board mechanically and contacts both rings electrically, standing in for the lost plating; its flared ends are then soldered to the rings. An eyelet restores a surface-to-surface (and, in a two-layer board, complete) through-connection, but it cannot re-plate a barrel deep inside a multi-layer board, which is via-repair work.
• swaging — the process of setting an eyelet or via rivet by flaring or spreading its ends outward against the surface on each side, using a setting tool that presses and rolls the rim over, so the rivet is locked mechanically into the hole and pressed into firm contact with the pad or annular ring on each face. Swaging is what turns a loose rivet in a hole into a secure, conducting through-connection, and setting the eyelet squarely by swaging — on a hole reamed clean and to size — is essential, because a skewed or under-set eyelet grips and contacts poorly.

Suggested Next Sections

Must read next:

• SMD and Fine-Pitch Pad Repair — Section 6.4 turns to the smallest and most demanding pads: the fine-pitch surface-mount and BGA lands where pads are tiny, close-packed, and unforgiving, and where the repair skills of this chapter meet their most exacting test.

Recommended:

• Rebuilding a Destroyed Pad — rebuilding a pad from fresh copper, which is how a broken annular ring is restored.
• Via Types: Through-Hole, Blind, Buried, Micro — plated holes and how a barrel connects the layers, the anatomy this repair works on.