BC Stringer
SML-S60 BC High-Speed Stringer — Built for Dense, High-Busbar, Thin Cells
A dedicated BC stringer. The three things a general-purpose stringer handles badly — cells packed nearly edge to edge, high busbar counts, and cells getting thinner every quarter — are the three it was designed around.
Not a TOPCon machine padded out to look like it does BC.
≥4800
pcs/h half-cell
≤±0.05
mm positioning
3BB–20BB
busbars · 25BB-ready
110–200
µm cell thickness
Half or third cells in → finished strings out
Where it sits
Where This Machine Sits
Before you review one parameter, place the machine. The SML-S60 owns a single station — stringing — in the middle of the module line. Everything this page covers happens inside that one station.
The machine reads two interfaces, not the whole line. In-feed: it takes half or third cells from scribing. Out-feed: it hands strings straight to a layup machine, or runs standalone.
Confirm the in-feed early
The machine expects cells already separated at scribing. If your upstream still snaps cells mechanically, the seam between the two stations is where integration risk sits — not inside the stringer. Docking to a layup machine on the out-feed needs that machine's height and dimensions supplied up front.
Who it's for
Who This Machine Is For
A dedicated BC machine is not a universal one. This split isn't about which machine is better — it's about which cell geometry each was built to hold, so you read the right spec sheet the first time.
Built for this machine
- BC cells, 166–210 mm — half or third cells, on the BC route.
- Both pitch gears — negative −1 to −0.5 mm for dense layouts a regular stringer can't shift into, plus positive 1–5 mm for standard spacing.
- High and rising busbar counts — 3BB–20BB today, 25BB-ready headroom.
- Thin cells — down to 110 μm, with the chipping boundary stated honestly below.
Not this machine — where to go
- PERC / TOPCon positive-pitch stringing — that route runs on the SML-S40, which has no negative pitch.
- Lower throughput or entry budget — the SML-S15 is the entry stringer.
Negative pitch is the capability line that separates a BC machine from a positive-pitch one, and the geometry behind it belongs to a page of its own. See the BC module line page → To weigh all three stringers side by side, see the tabber stringer machine page →
Full spec
Full Specification
This is the table your process team reads line by line — nothing hidden, nothing cherry-picked, and the boundaries marked where a number stops holding. The reasons behind the numbers live in the sections that follow; this one is the checklist.
One boundary is on the table on purpose: chipping rate holds at ≤0.25% on A-grade cells at 120 μm and above — go thinner and it rises. If you cut on the thin edge, that row is the one to check against your route.
| Parameter | Value |
|---|---|
| Cell | |
| Applicable cell | BC, 166–210 mm, half / third cell |
| Busbar count | 3BB–20BB, 25BB-ready |
| Cell thickness | 110–200 μm |
| Throughput | |
| Capacity | half-cell ≥4800 pcs/h |
| Utilization | ≥95% |
| Chipping rate | ≤0.25% (A-grade)Holds at ≥120 μm; rises on ultra-thin cells. |
| Precision | |
| Positioning accuracy | ≤±0.05 mm; angle ≤±0.04° |
| Robot repeatability | 0.01 mm (four-axis) |
| String length | 540–1400 mm |
| String straightness | ±0.5 mm |
| Cell pitch | negative −1 to −0.5 mm; positive 1–5 mm |
| Pitch accuracy | ±0.3 mm |
| Seam exposure | ≤±0.3 mm |
| Welding | |
| Method | infrared; blue-film down, tooling presses ribbon; flux by ribbon dip |
| Temperature control | ±7.5 °C (host high/low limits, over-limit alarm) |
| Weld pull force | ≥0.5 N (0.6 mm flat ribbon) |
| String defect rate | ≤3% |
| Overlap-return rate | ≤15% |
| Feeding | |
| Ribbon feeding | 20 feed motors, upgradable to 25 busbars |
| Ribbon spool | max 12 kg; bore 16/20 mm, OD ≤180 mm, width ≤160 mm; leaded / lead-free |
| Magazine capacity | 200 small cells |
| Detection | |
| Defect detection | missing corner, chipping, cracks, print skew and offset (host-definable) |
| Inline inspection | string appearance + string EL — optional |
Ribbon feeding module
200-cell magazine
Upgrade path
Step Up Busbars Without Changing the Machine
Of everything on the table above, busbar count is the spec most likely to move under you within a year — the BC route keeps stepping toward higher numbers, and the roadmap you sign this year is rarely the one you run next.
Get it wrong and the cost is not small. If a machine is locked to today's busbar count, a step up means a new machine — re-commissioning, re-qualifying, and a stop on the line while you swap it. A single spec you couldn't upgrade drags your whole capacity plan back to the drawing board.
So the feeding module is built to move. Twenty feed motors cover 3–20 busbars, each selectable at the host so you run only what the string needs. Stepping up to 25 busbars is a tooling change, not a new machine — the frame, the transport and the robot all stay.
So a busbar-count change is a changeover, not a rebuild. The count you actually run is set at the host within the 3–20 range; the matching guide tooling for that layout is swapped in, and that tooling is a separately billed item. What none of it touches is the machine you commissioned.
The evidence is checkable before you order. The head is 25BB-ready, and the ribbon spool takes these three — hold your current spool against them and you'll know on the spot whether your ribbon runs on it.
≤12 kg
Spool weight
16 / 20 mm
Bore
≤180 mm
Outer diameter
If your current spool sits outside those limits, that's a consumable to align before commissioning, not a machine limit — the feed takes both leaded and lead-free ribbon either way. What a full changeover involves end to end has a page of its own. See the cell compatibility and changeover page →
Solder strength
Where Solder Strength Is Won
Whether a joint holds is decided upstream of the weld itself — in the flux and the temperature. Stabilize those two at the source and you stop manufacturing weak joints, which is cheaper than catching them after the fact.
Flux by ribbon dip
The ribbon is fluxed by immersion, so every ribbon carries flux into the joint evenly — not by a spray that can run dry or uneven.
Infrared welding
The cell runs blue-film side down and tooling presses the ribbon flat to the pad, so the joint forms under controlled contact instead of a floating ribbon.
Temperature held to ±7.5 °C
The host sets high and low limits and alarms on any excursion, so a drifting profile is caught as it drifts, not at inspection.
A weak joint made here isn't free to fix later — it's reworked at the string, or found at EL after it has already traveled downstream. The over-limit alarm is what turns a slow thermal drift into a caught event.
Flux dip
Infrared
The numbers
The Three Numbers Behind the Yield
These are the numbers your rated capacity is signed against. No reading required — glance and you know the class.
≥0.5 N
Weld pull force, 0.6 mm flat ribbon
≤3%
String defect rate
≤15%
Overlap-return rate
Pull force is measured per busbar line, with at most one point below 0.5 N allowed on any line — a floor, not an average that hides a weak joint.
Alignment & reject
How the Robot Holds Alignment and Rejects Bad Cells
The four-axis robot does two jobs, and both matter more on a BC cell than on a regular one: it rejects NG cells before they reach the string, and it micro-aligns every cell so each busbar lands on its ribbon. BC cells sit densely, with far less geometric tolerance than a conventional layout — the robot is what closes that margin.
- 1
It rejects NG cells
Onboard defect detection reads each cell for missing corners, chipping, cracks, and print skew or offset, all host-definable, and pulls the bad ones out. One defective cell welded into a string takes the whole string down — catching it at the pick is the cheapest place the stringer can.
- 2
You tune what counts as a reject
Because those categories are host-definable, you tighten it for a fragile thin cell or set it to your print-quality tolerance — rather than living with a fixed factory threshold. A rejected cell is pulled before placement.
- 3
It micro-aligns every cell
Robot repeatability is 0.01 mm and comprehensive positioning holds ≤±0.05 mm with angle ≤±0.04°. That precision is what keeps seam exposure inside ≤±0.3 mm, cell after cell.
Why seam and pitch consistency decides the module's EL result is argued in full on the home page — see seam and pitch consistency → This section is the machine doing it, not the case for why it matters.
Inline EL
Inline EL Is Optional — Read the Trade-off
String appearance inspection and string EL inspection for cold solder and hidden cracks are optional equipment, not standard. Both configurations are legitimate; which one fits depends on where you want to catch a defect.
With inline ELOptional
- Cold solder and hidden cracks are screened at the string, right as it leaves the machine.
- The defect is caught before it can ride forward into layup.
Without inline EL
- The weld process and the pull-force floor carry the load.
- The ≥0.5 N criterion and the ≤3% defect rate are what you lean on to keep bad joints out.
It's offered rather than fixed because lines differ: some already run a standalone EL station downstream, while others want cold solder and hidden cracks caught the moment they're made. A defect that slips past here stays invisible until EL — which is why the choice is worth making deliberately.
Tell us your line's downstream inspection and we'll adviseRuns continuously
Built to Run Continuously
A stringer earns its throughput only if it doesn't stall on loading or handoff — on a line rated by capacity, an unplanned stop at either quietly eats the number you signed for.
-
200-cell magazine
Feeds the machine long enough that reloading doesn't break the takt.
-
Cycling weld tooling
Tooling presses each ribbon and cycles back, so welding runs without a manual reset.
-
String outfeed
Hands strings to a layup machine, or runs standalone. Docking-height detail lives on the SML-A6 layup page.
Your floor
Measure Your Floor First
Start with the weight — it is where the SML-S60 asks the most of your building: at 7000 kg it is the heaviest machine on this line, against the S40's 4500 kg and the S15's 3000 kg, so the constraint is getting a frame this heavy craned in and set on a slab rated to carry it.
| Item | SML-S60 |
|---|---|
| Footprint | 8050×2800×2500 mm |
| Weight | 7000 kg |
| Power | avg 30 kW, peak 45 kW |
Other stringers
Not BC? Two Other Stringers
Both other stringers carry the same 3BB–20BB busbars this machine does, so stepping off the SML-S60 doesn't cost you busbar range — it costs you a route, and one capability in particular. The S60 is the only one of the three that lays negative pitch; the moment you leave it, that gear is gone, because both machines below run positive pitch only.
SML-S40 — Multi-Busbar Stringer
Same busbar range, TOPCon/PERC route, positive pitch only — no negative-pitch overlap layout. Where you go when the design doesn't pack cells edge to edge.
CompareSML-S15 — Entry Stringer
The entry-tier TOPCon/PERC machine, also positive pitch only, for lower throughput or a smaller starting budget.
CompareFor the full side-by-side of all three stringers, see the tabber stringer machine page →
After you buy
After You Buy
The pull-force line on the acceptance table hides a tolerance most buyers read as an absolute.
Read the one-point tolerance in the pull-force test
The SML-S60 is signed off at ≥0.5 N, but the criterion allows one point per busbar to fall below 0.5 N — a single low reading does not fail the weld. Miss that clause and you either reject a sound line or hold it to a floor the agreement never set; carry the tolerance into your acceptance run exactly as written, and ≥0.5 N is judged the way the machine was built to be judged.
See how acceptance is runGet a proposal
Get Your Configuration Proposal
Send the cell spec, get a proposal back — the low-effort next step, before any commitment.
Reply within 24 hours · by email.