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1.5 Common Defects & Corrections

Most soldering defects stem not from mystery but from a handful of predictable missteps in preparation, heat, or exit. Bridges, icicles, and skips all trace back to flux coverage, top-side activation, wave balance, or nozzle control—and each has a small, reliable correction. By treating symptoms with the lightest adjustment and confirming results on a single panel, the process stays both stable and teachable.

1.5.1 Triage first (don’t turn five knobs)

  1. Prep check (always first): flux coverage/dose and top-side temp at wave entry (1.2).
  2. Mechanics: pallet seals/clearances, finger cleanliness/angle (1.4.4), nozzle Z/height (1.3.6).
  3. Process knob: change one—speed/dwell, fountain height, chip↔main balance—then recheck on one panel.



1.5.2 Quick map (symptom → likely cause → smallest fix)

Symptom

Likely cause(s)

First fix (fastest that sticks)

Bridging (between pins/rows)

Flooded flux film; cold entry; chip wave too low/short; parallel long rows; fountain too tall

Trim flux dose; add/extend chip wave dwell +0.3 s; raise top-side 5–10 °C; lower fountain 0.2–0.5 mm; rotate layout vs wave or add thief (13.1/13.4)

Bridging at row end

Lazy exit; no tail

Add end-dwell 0.3–0.5 s then quick kick-out; program a thief tail past last pad; sharpen pallet exit edge

Icicles / spears

Over-dwell with cool exit; low pot; long lead protrusion

Faster exit; +5 °C pot; trim dwell −0.2 s; enforce 0.5–1.5 mm protrusion (12.1)

Skips / non-wet / de-wet

Oxide/aged finish; flux starved; short contact; thermals to planes

Add light extra spray pass; slow belt (longer contact); 4-spoke thermals in next rev; try N₂ on wave

Poor top-side barrel fill

Inadequate preheat/flux in holes; drag too fast; hungry copper/planes

Raise top-side temp 5–10 °C; second light pass; reduce speed 2–3 mm/s or +0.3 s spot-dwell; bump pot +5 °C if still short

Solder balls / spitting

Wet solvent at entry; fountain turbulence; dirty fingers

Dry earlier (same total heat, smoother ramp); lower fountain 0.5–1.0 mm; clean/degunk fingers & rails

Blowholes / voids in barrels

Moist PCB; flux boils in hole; mask dams gas

Bake boards; gentler, longer preheat; relieve mask annulus 0.10–0.15 mm (13.1)

Dull/grainy joints

Cold joint; over-baked flux

+5 °C pot or +0.2 s main dwell; even preheat (no burnt zones); consider N₂

SMT splash / contamination

Overspray; fountain too tall; masking gaps

Tighten spray window; lower fountain; improve pallet seal and add clip-on fences

Selective: random non-fill

Z too high (no engulf); path outruns cup

Touch-off Z-zero; slow to 5–8 mm/s on that segment; add quick-wet + targeted slow second pass

Selective: persistent bridges in 2.00 mm rows

Cup overfills trench; end dwell missing

Smaller non-wettable nozzle; add end-dwell + kick; 5–10° approach angle



1.5.3 Root causes you can design out (next spin)

  • Holes too tight / thin annular rings → undersized barrels never fill. Fix: lead Ø +0.20–0.45 mm (by thickness/copper), annular ≥0.25–0.30 mm, teardrops (1.1).
  • No thermal reliefs to planes → cold joints. Fix: 4 spokes, 0.25–0.40 mm (1.1).
  • Rows parallel to wave → long solder dams. Fix: rotate or add robber pads/pallet thieves (1.1, 1.4).
  • SMT crowding miniwave → splash/bridges. Fix: 3–4 mm keepout or pallet masking (1.1, 1.3).
  • Leads too long → icicles. Fix: plan protrusion 0.5–1.5 mm after solder (1.1).



1.5.4 Knob guide (change the right thing)

  • Looks flooded / bridges early? → Flux & preheat first, then chip wave height/dwell.
  • Looks starved / no top-fill? → Conveyor speed & dwell, then pot +5 °C.
  • Exit looks stringy? → End-dwell + quick lift, small air/N₂ knife; don’t just raise temperature.
  • Selective only on a few pins failing? → Local pass (spot dwell) and smaller nozzle, not global changes.



1.5.5 Mini playbooks (by defect)

A) Bridging (fine rows)

  1. Verify UV flux carpet and top-side in band (1.2).
  2. Raise chip 0.2–0.5 mm or +0.3 s dwell; keep main calm.
  3. Add end-dwell + kick; if still there → lower main 0.2 mm and add thief.
  4. Next rev: robber pad or pallet tail.

B) Poor top-side fill

  1. +5–10 °C top-side via preheat; slow belt or +0.3 s spot-dwell.
  2. Second light pass (drag or selective).
  3. If still low → +5 °C pot; check hole clearance/thermals for next spin.

C) Icicles on tabs/posts

  1. Faster exit; small knife.
  2. +5 °C pot; shorten dwell; confirm lead protrusion.
  3. For huge tabs: mini-dip or local spot dwell, not whole-board heat.



1.5.6 Selective vs wave: what’s different

  • Selective fixes are local: nozzle Ø, Z touch-off, path speed/dwell, fountain height. Prefer two-stage passes (quick wet → slow finish).
  • Wave fixes are global: chip↔main balance, conveyor angle, peel/knife. Don’t try to make main wave do chip’s job.



1.5.7 “Do not” list (saves days)

  • Don’t raise pot temp to fix flux/preheat mistakes—spatter and oxidation follow.
  • Don’t widen AOI limits for bridges; fix chip wave / exit.
  • Don’t drown boards in flux; dry, even films beat puddles.
  • Don’t tweak three settings at once—you lose the cause.
  • Don’t accept “random non-fill” until you’ve checked hole size vs lead.



1.5.8 Tiny DOE when you’re stuck (3× panels)

  • Factor A: Speed (−2 mm/s / nominal / +2 mm/s)
  • Factor B: Fountain (−0.3 mm / nominal / +0.3 mm)
  • Factor C: End-dwell (0 / +0.3 s)
    Measure bridges/row, top-fill %, icicles. Keep the combo that improves the Pareto with the smallest heat.



1.5.9 Inspect what proves the fix

  • Top-side barrel photos on the worst header (same pads each run).
  • Count bridges per row, icicle length, skip rate on 3 panels before/after.
  • Save settings in recipe comments (what you changed and why).



1.5.10 Pocket checklists

Before first article

  • Flux pattern even; dose logged; no overspray
  • Top-side temp at entry in band (per flux family)
  • Chip and main heights set; angle 6–8°; finger path clean
  • Selective: Z-zero taught; nozzle Ø sized to pad +1–2 mm

If bridging

  • Add/extend chip; lower main a touch; end-dwell + kick
  • Thief tail or pallet insert; re-photo same row

If non-fill / skips

  • Slow belt or +0.3 s spot dwell; raise top-side 5–10 °C
  • Second light pass; check hole/thermal design for next rev

If icicles

  • Faster exit; light knife; +5 °C pot only if needed
  • Verify lead protrusion; shorten dwell on tabs



The path to fewer defects is disciplined troubleshooting: verify flux and preheat first, change one knob at a time, and log what works. This approach eliminates recurring issues, strengthens recipes, and ensures that quality is sustained instead of rediscovered.


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