Soldering SOIC and Wide-Body ICs

Section Overview

You've soldered a few-legged SOT and a small IC (6.4); a wide-body SOIC just has more of the same — two long rows of gull-wing legs. The small-outline integrated circuit (SOIC) is the wide-body gull-wing IC — op-amps, logic, microcontrollers — with eight to twenty-eight or more pins, and it is one of the most hand-solderable ICs there is, because its classic pitch of 1.27 mm is relatively coarse for surface-mount, giving you room between pins. Its narrower-pitch relatives — the shrink small-outline package (SSOP) and the thin shrink small-outline package (TSSOP) — pack the legs closer and are harder, while QFN and BGA remain hot-air-only (6.1). The method is the corner-tack of 6.4, scaled up: find pin 1 (6.4), flux, place the part square so every foot sits on its pad, tack one corner, check alignment and coplanarity (6.4), then tack the diagonally opposite corner to fully lock the part's rotation before you solder the rest. Then solder the two rows one of two ways. Point-by-point: one small concave fillet per pin (5.3) — slower but reliable. Or flood-and-wick: deliberately flow solder along a whole row, bridges and all, then drag desoldering braid down the row to wick away the excess and leave clean individual fillets (5.5) — faster, and the stepping-stone to the true drag soldering of Chapter 7. Both depend on generous flux, and both end the same way: wick any remaining bridge and inspect every pin for a concave fillet and every foot for contact (5.4; 6.7). Find pin 1, tack two diagonal corners, solder the rows, wick the bridges, and check every pin — the wide-body IC made manageable.

Why This Matters

The wide-body SOIC is the workhorse IC package of hand-solderable boards, so this is the section that lets you install and replace the chips that run the circuit. This matters because SOIC is genuinely approachable: its coarse 1.27 mm pitch means the legs are far enough apart that a steady hand, flux, and a fine tip make clean joints without a microscope — so the intimidating-looking multi-pin chip is, in practice, one of the friendlier parts to solder. It matters because the two-corner tack is what tames a long part: one tacked corner can still pivot, but two diagonal corners fix both position and rotation, so the rows of legs stay locked on their pads while you work down them — without it, a long IC creeps and lands with legs off their pads. It matters because flood-and-wick is a genuine time-saver and a skill in its own right: learning that you can intentionally over-apply solder and then wick it clean (5.5) turns a daunting row of pins into two quick passes — and it is the direct precursor to drag soldering (Chapter 7). It matters because bridges are inevitable on close rows and must be cleared, not feared: the habit of flux-and-wick means a bridge is a two-second fix, not a ruined board. It matters because inspection scales with pin count: a 28-pin IC has 28 chances for a cold joint, a lifted leg, or a bridge, so checking every pin and every gap is part of the job (5.4; 6.7). And it matters because these skills transfer directly upward: the two-corner tack, the flood-and-wick, and the per-pin inspection are exactly what you use on finer-pitch SSOP and TSSOP parts and, with hot air, on the packages an iron can't reach (Chapter 8). Master the SOIC and the active heart of almost any hand-solderable board is within reach.

Required Prerequisites

• Soldering SOT and Small IC Packages — Section 6.4 taught the corner-tack, coplanarity check, and one-lead-at-a-time method on small multi-lead parts; this section scales it to longer rows. You should be comfortable finding pin 1, tacking a corner, and making a clean concave fillet (6.4; 6.3; 5.3), and you should have desoldering braid and know how to wick a bridge (5.5), plus a fine tip and plenty of flux (Chapters 4 and 3).

Recommended Consumables

• Flux — generously (Chapter 3) — essential for both point-by-point and flood-and-wick
• Thin flux-cored solder — for metering per-pin joints and flooding a row
• Desoldering braid (5.5) — central to flood-and-wick and to clearing bridges
• Scrap boards with SOIC and wide-body IC parts (SOIC-8 up to SOIC-28, 6.1) — to practice on long rows
• Isopropyl alcohol and a brush — to clean flux and inspect every pin (5.4)
• Eye protection and ventilation — flood-and-wick moves molten solder and hot braid, and uses a lot of flux (Chapter 3)

Recommended Practice Hardware

• A fine soldering tip — a small conical, bent, or short chisel tip (Chapter 4) — fine for point-by-point; a small chisel also suits flood-and-wick
• Fine anti-magnetic tweezers — to place and hold the part (6.4)
• A magnifier — loupe, visor, or bench magnifier lamp (Volume 2, Chapter 9) — to place, check coplanarity, and inspect every pin
• A board holder or vise — to steady the board while you work down a row
• An ESD-safe surface — ICs are static-sensitive

Real-World Applications

Soldering wide-body ICs is the everyday work of installing and replacing the chips that make a board do its job. A technician replacing a failed op-amp in an SOIC-8 finds pin 1, tacks two diagonal corners, and solders the two short rows point-by-point in under a minute. Someone installing a 20-pin microcontroller tacks opposite corners to lock it, then flood-and-wicks each long row — flowing solder down the row and dragging braid to leave clean fillets (5.5) — finishing far faster than one pin at a time. A repairer who kept getting crept, crooked ICs learns the two-corner tack: lock both corners first and the part cannot walk. Someone whose row came out full of bridges discovers that flux and a pass of braid clear them all in seconds — the bridges were expected, not a disaster. And a builder working a dense board develops a rhythm on the ICs: pin 1, corners, rows, wick, inspect — the same sequence on every chip. The failures this skill prevents: the IC soldered crooked or a pin off, the lifted leg that never connects, the bridge left as a short, and the cold joint hidden in a long row. Nearly every hand-solderable IC on a board goes down by this two-corner, row-by-row method — and it is the foundation the finer-pitch and hot-air work builds on (Chapters 7-8).

Common Challenges

• The IC creeps or rotates while I solder the rows. One corner tack still lets it pivot — tack two diagonal corners to lock rotation before soldering any row (6.4).
• My rows come out full of bridges. That's expected with flood-and-wick, and easy with point-by-point too — flux generously and drag desoldering braid down the row to wick the excess (5.5); use less solder if you're going point-by-point.
• One pin in the middle of a row isn't connected. That leg may not be coplanar (lifted off its pad) (6.4) or the joint is cold — check every foot is down, and reflow any dull joint with flux.

Safety Notes

Risk Level: Low. This is hot work, and flood-and-wick in particular moves a lot of molten solder and uses hot braid, so eye protection and ventilation matter.

Professional Tips Before Starting

• Lock rotation with two diagonal corners. One corner tack holds position but lets the part pivot — tack the diagonally opposite corner too, and the long IC cannot creep or rotate while you solder the rows (6.4).
• Don't fear bridges — flux and wick them. Whether you go point-by-point or flood-and-wick, a bridge is a two-second fix: add flux and drag desoldering braid down the row (5.5); fear of bridges leads to starved joints instead.
• Inspect every single pin. A long row has many chances for a cold joint, a lifted leg, or a bridge — check each pin for a concave fillet and each foot for contact, and sweep every gap (5.4; 6.7).

Soldering Wide-Body ICs — SOIC, Two-Corner Tack, and Flood-and-Wick

From Small ICs to Wide-Body SOIC

A wide-body IC is just a small multi-lead part with more legs, arranged in two longer rows — and that length is the only thing that changes the method. A SOT or small IC has a handful of legs (6.4); a wide-body SOIC has two rows of gull-wing legs down its long sides, from eight pins up to twenty-eight or more. The core routine is unchanged: find pin 1, place square, tack, verify, and solder each leg into a concave fillet (6.4; 5.3). What length adds is the need to lock the part more firmly and to work systematically down long rows. A single corner tack held a small part, but a long IC tacked at just one corner can still pivot around that point and drift out of line as you work — so you tack two diagonal corners to fix both ends. And a long row of legs invites bridges and demands that you check every pin, not just glance at a few. So think of the wide-body IC as the small-IC method plus two disciplines: a two-corner tack to lock a longer part, and a row-at-a-time approach — point-by-point or flood-and-wick — to solder and clean many legs efficiently.

The SOIC Package and Its Forgiving Pitch

The single most encouraging fact about wide-body ICs is that the classic SOIC is one of the easiest ICs to hand-solder, because of its pitch. The small-outline integrated circuit is a wide-body gull-wing IC package (6.1) holding op-amps, logic, sensors, and microcontrollers, in common sizes from SOIC-8 to SOIC-28. Its classic lead pitch is 1.27 mm — which is coarse by surface-mount standards — so the legs sit comparatively far apart, leaving room to place solder on one pin without immediately bridging to the next. That generous spacing is why SOIC forgives a slightly-too-large tip or a little extra solder in a way a fine-pitch part never would. Its narrower relatives tighten that up: the shrink small-outline package (SSOP) squeezes the pitch smaller, and the thin shrink small-outline package (TSSOP) is thinner still and finer-pitch — both hand-solderable but less forgiving, demanding more flux, a finer tip, and often the flood-and-wick approach. Beyond those, the no-lead QFN and ball-grid BGA cannot be hand-soldered at all and need hot air (6.1; Chapter 8). So when you meet a wide-body gull-wing IC, check the pitch: a 1.27 mm SOIC is a friendly job, while an SSOP or TSSOP is the same method executed finer.

Two-Corner Tack and Placement

Locking a long part takes two tacks, not one, and placing it right comes first. Find pin 1 using the pin-1 indicator and match it to the board's silkscreen (6.4) — on a multi-pin IC, orientation must be right or every pin is wrong. Flux the pads, and place the part square with tweezers so every leg foot sits on its own pad, aligned down both rows (6.4). Now tack one corner: reheat a pre-tinned corner pad or add a touch of solder to that corner leg, anchoring the part. Check the alignment and coplanarity (6.4): is pin 1 right, is the part square, is every foot on its pad? If it's slightly off, reheat that one corner and nudge it true — with one corner tacked, the part still pivots. Once it's aligned, tack the diagonally opposite corner: this second tack fixes the rotation, so the part is now locked in both position and angle and cannot creep while you solder the rows. Two diagonal corners, not two adjacent ones — diagonal corners pin down the whole rectangle. With the part locked and verified, you're ready to solder the rows: placement checked, pin 1 confirmed, every foot down, both corners tacked.

Soldering the Rows — Point-by-Point and Flood-and-Wick

With the part locked, there are two good ways to solder the rows, and both rely on flux. The first is point-by-point: solder each leg individually — touch the iron to the pad and the gull-wing foot, feed a little thin solder, and let it flow into a small concave fillet (5.3) — working down the row one pin at a time. It is slower but very reliable and the best way to learn. The second is flood-and-wick: you deliberately flow solder along a whole row at once — running the iron and solder down the legs and accepting that adjacent pins bridge together — and then you drag a piece of desoldering braid down the row, which wicks up the excess solder and lifts the bridges, leaving a clean concave fillet on each pin (5.5). It sounds backwards to make bridges on purpose, but it is fast and effective: the flux and braid do the separating. Flood-and-wick needs generous flux to work cleanly, and it is the direct precursor to true drag soldering, where a shaped tip carrying a bead of solder draws down the row and leaves clean joints in one pass (Chapter 7). Either method finishes the rows: point-by-point for control and learning, flood-and-wick for speed — and both end with a bridge check.

Thermal Mass and Heat

A wide-body IC has more body and metal than a chip, so its thermal mass shapes how you deliver heat. Thermal mass is the amount of heat a part and its pads can absorb — a bigger IC, wider pads, and ground-plane connections all soak up more heat, so a joint that is slow to reach temperature is usually a heat-delivery problem, not a reason to linger (the diagnostic from 5.3). The answer is the same as always but matters more here: an adequately hot tip, a clean tinned tip carrying a little solder to bridge the heat in, and generous flux so the joint wets quickly — so each joint reaches temperature and flows in a second or two rather than needing a long, part-cooking dwell. The good news is that SOIC's coarse pitch and modest size keep this easy: the joints are not large and the legs are well spaced, so a normal fine-tip setup handles them without trouble. Watch the component, though: ICs are heat-sensitive, so heat efficiently and don't dwell — and for a very large or ground-plane-connected part, gentle preheating (hot air, Chapter 8) helps the joints reach temperature without cooking the chip. Deliver heat well and briefly, and thermal mass is a non-issue on a SOIC.

Bridges, Cleanup, and Inspection

The row is not done when the last pin is soldered — it's done when you've cleared every bridge and inspected every pin. Bridges are the expected fault on close rows — a solder bridge spans two adjacent legs (5.4) — and with flood-and-wick you make them deliberately, so clearing them is routine: add flux and drag desoldering braid along the bridged pins (5.5), and the excess lifts away leaving separate fillets. After the rows are soldered and wicked, inspect systematically (5.4; 6.7): look at every pin for a small, smooth concave fillet climbing from the pad onto the gull-wing foot; sweep every gap between legs for a remaining bridge, tilting the board under magnification; and confirm coplanarity — that no leg is lifted off its pad (6.4). Reflow any cold or starved joint with flux, wick any bridge you find, and true and reflow any lifted leg. On a long IC this per-pin discipline matters: one missed bridge is a short and one lifted leg is an open, and either can be lost among many good joints if you don't check each one. Clean flux residue and look again — a wide-body IC is done when every pin shows a good fillet, every gap is clear, and every foot is down.

Common Mistakes

• Tacking only one corner of a long IC. It can still pivot and creep — tack two diagonal corners to lock both position and rotation before soldering (6.4).
• Fearing bridges into starved joints. Bridges are a routine, two-second fix — flux and wick them with braid (5.5); don't under-solder to avoid them.
• Not finding pin 1 first. A multi-pin IC soldered rotated is wrong on every pin (6.4) — match the pin-1 indicator to the silkscreen before tacking.
• Lingering on a slow joint. A big IC's thermal mass means a slow joint is a heat-delivery problem — hotter tip, more flux, a heat bridge, not a longer dwell (5.3).
• Inspecting only a few pins. A long row hides a cold joint, a bridge, or a lifted leg — check every single pin and gap (5.4; 6.7).

Troubleshooting Guidance

Wide-body IC problems trace back to placement, heat, bridges, or an unchecked pin. If the IC creeps or rotates: you tacked only one corner — tack two diagonal corners first (6.4). If the part is rotated or a pin off: you skipped the pin-1 check — desolder and reinstall correctly (5.5), matching the pin-1 indicator. If a row is full of bridges: expected — flux and drag braid down it (5.5); if going point-by-point, use less solder. If a middle pin has no connection: a lifted (non-coplanar) leg or a cold joint (6.4; 5.4) — check every foot is down, true any lifted leg, and reflow with flux. If a joint is slow to flow: the part's thermal mass is winning — hotter tip, more flux, a heat bridge, not a longer dwell (5.3). If a joint is dull or grainy: cold or disturbed (5.4) — reflow with flux and hold still. If bridges keep reappearing after wicking: not enough flux, or too much solder went on — add flux, use fresh braid, and meter less solder. The throughline: lock two corners, deliver heat well, expect and wick bridges, and inspect every pin — and a wide-body IC goes down cleanly.

Verification & Testing Methods

Use this as a wide-body IC check:

• [ ] I find pin 1 and place the part square so every leg foot sits on its pad.
• [ ] I tack two diagonal corners to lock the part's position and rotation before soldering the rows.
• [ ] I solder each row point-by-point into concave fillets, or use flood-and-wick — flowing solder down the row then dragging braid to leave clean fillets (5.5).
• [ ] I flux generously and deliver heat efficiently so joints wet quickly despite the part's thermal mass.
• [ ] I wick away every bridge with braid and confirm no leg is lifted (coplanarity, 6.4).
• [ ] I inspect every pin for a small concave fillet and sweep every gap before calling the part done (5.4; 6.7).

Then try the practice exercises below — wide-body IC soldering practice; scenarios differ from the quiz.

Practice Exercises

1. Solder an SOIC-8 point-by-point (8 minutes, applied). On scrap, find pin 1, tack two diagonal corners, and solder both short rows one pin at a time into small fillets. Inspect every pin (5.4).
2. Flood-and-wick a long row (10 minutes, applied). On a larger SOIC, flood one row with solder (bridges and all), then drag fluxed desoldering braid down it to leave clean fillets (5.5). Compare the speed to point-by-point.
3. Lock with two corners (5 minutes, applied). Tack only one corner and feel how the part still pivots; then tack the diagonal corner and confirm it's locked. Describe the difference.
4. Inspect a whole IC (6 minutes, reasoning). Describe how you would inspect every pin of a 20-pin SOIC for cold joints, bridges, and lifted legs, and how you'd fix each.

These core ideas — scaling the corner-tack to wide-body ICs, SOIC's forgiving pitch, the two-corner tack, point-by-point and flood-and-wick, and per-pin inspection — are tested in the Chapter Quiz at the end of this chapter, where a score of 80% is required to continue.

Key Takeaways

• A wide-body IC is the small-IC method scaled up: find pin 1, place square, tack two diagonal corners to lock a longer part, solder the rows, wick bridges, and inspect every pin (6.4).
• The small-outline integrated circuit (SOIC) is one of the most hand-solderable ICs because its classic 1.27 mm pitch is coarse and forgiving; its finer-pitch relatives the shrink small-outline package (SSOP) and thin shrink small-outline package (TSSOP) are the same method executed finer (6.1).
• Tacking two diagonal corners locks both position and rotation — one corner alone still lets a long part pivot and creep off its pads.
• Solder the rows point-by-point (one concave fillet per pin, reliable) or with flood-and-wick (flow solder along the row, then drag braid to leave clean fillets) (5.5) — both need generous flux, and flood-and-wick is the precursor to drag soldering (Chapter 7).
• A long row hides faults, so clear every bridge with braid (5.5) and inspect every pin for a concave fillet and every foot for contact (coplanarity, 6.4; inspection, 5.4/6.7) before calling the IC done.

Skills Learned

• You can now hand-solder a wide-body SOIC using the two-corner-tack method.
• You can now explain why SOIC's coarse pitch is forgiving.
• You can now tack two diagonal corners to lock a part before soldering.
• You can now solder a row point-by-point or with flood-and-wick.
• You can now clear bridges and inspect every pin for a good fillet.

Glossary Additions

• small-outline integrated circuit — a wide-body surface-mount integrated-circuit package with two rows of gull-wing leads down its long sides, abbreviated SOIC and made in common sizes from SOIC-8 to SOIC-28 or larger; its classic lead pitch of 1.27 mm is relatively coarse for surface-mount, which leaves comfortable space between pins and makes the SOIC one of the most forgiving integrated circuits to hand-solder. SOICs hold op-amps, logic, sensors, and microcontrollers, and are soldered by tacking two diagonal corners and then soldering the rows.
• shrink small-outline package — a surface-mount integrated-circuit package similar to the SOIC but with a smaller, finer lead pitch, abbreviated SSOP, which packs more pins into a given length at the cost of being harder to hand-solder; an SSOP is still gull-wing and hand-solderable, but its closer legs demand more flux, a finer tip, and often the flood-and-wick method to control bridges. It sits between the coarse SOIC and the finer TSSOP in difficulty.
• thin shrink small-outline package — a thin, fine-pitch surface-mount integrated-circuit package with two rows of gull-wing leads, abbreviated TSSOP, that is both lower-profile and finer-pitch than an SSOP; it is hand-solderable but among the more demanding gull-wing packages, needing generous flux, a fine tip, magnification, and usually the flood-and-wick approach to keep the closely-spaced legs from bridging. Like the SOIC and SSOP, its leads are visible and reachable, unlike a no-lead or ball-grid package.
• flood-and-wick — a hand-soldering method for a row of closely-spaced IC leads in which solder is deliberately flowed along the whole row, deliberately bridging adjacent pins, and then desoldering braid is dragged down the row to wick away the excess solder and lift the bridges, leaving a clean concave fillet on each pin; it depends on generous flux to work cleanly and is faster than soldering pin by pin. Flood-and-wick is the practical precursor to true drag soldering, in which a shaped tip carrying a bead of solder draws down the row in one pass.

Suggested Next Sections

Must read next:

• SMD Desoldering — Wick and Iron — you can now solder surface-mount parts from chips to wide-body ICs; the next section teaches the removal side: how to take SMD parts off cleanly with desoldering braid and an iron, so you can replace failed components and fix the faults you find — the surface-mount counterpart to the through-hole desoldering of 5.5.

Recommended:

• Soldering SOT and Small IC Packages — the corner-tack, coplanarity, and one-lead method this section scales up.
• SMD Component Overview — Sizes and Packages — the packages and pitch that decide which ICs a hand iron can solder.