S100B Desktop Selective Soldering Machine for High-Mix THT

When you run dozens of board variants in small batches, THT soldering is usually the most stubborn bottleneck on the floor.

Hand soldering is slow and operator-dependent. Full-size wave soldering needs dedicated pallets and long changeover. A large in-line selective system is hard to justify at low utilization. The S100B desktop selective soldering machine from Southern Machinery fills exactly that gap: a compact, fixture-less station built for ultra-fast changeover in high-mix, low-volume (HMLV) THT production. This guide gives you a framework to judge the fit before you request a quote.

Why high-mix THT soldering stalls

The pain is rarely the solder joint itself — it is everything around it:

• Hand-solder variance. Joint appearance, wetting and dwell time shift with skill, shift and fatigue; rework on a dense board risks pad damage.
• Fixtures are a hidden tax. Boards with THT on both sides, or with tall and heat-sensitive parts, need carriers, masks or pallets — one tooling set per variant, and a changeover penalty each time.
• Big lines sit idle at low volume. A full in-line selective system pays off at high utilization; for NPI, rework and small batches, it is often oversized.
• Slow changeover kills HMLV throughput. If every batch costs 30–60 minutes of pallet, program and parameter swaps, effective capacity collapses as batch size shrinks.

The Fixture-Less Fit Test

Run this on your current process — no machine required:

1. Count variants per day. How many distinct board models see the soldering station in a typical day?
2. Inventory your tooling. How many pallets, carriers or masks do you own, and how many are single-variant?
3. Time a changeover. From last board off to first good board of the next variant, how many minutes?
4. Tally hand-solder rework. Over the last month, how many THT joints were reworked by hand, and what did pad damage cost?

If the test shows many variants, per-variant tooling and long changeovers, a fixture-less design is the lever — not a bigger machine.

The Vehicle: how the S100B works

Instead of passing the whole board over a full-width wave, selective soldering applies flux only where needed, then moves a small nozzle (or mini-wave) along a programmed path to solder each joint individually. Because the board is held by a programmable motion platform rather than a dedicated carrier, the S100B changes between PCB models by recalling a stored program — no pallet, no fixture, no mechanical changeover.

• Load a PCB, recall the program, run. The next variant is another file, not another tooling set.
• Repeatable joints. The same dwell time, wave height and Z height apply to every joint on every board, removing operator-to-operator variation that drives rework.
• Traceable recipes. Programs, solder temperature, flux and motion paths are stored per PCB — the same logic Southern Machinery documents for its SL-600 mini selective machine, whose PC software stores the full PCB menu (dimensions, flux type, solder type, nozzle, temperatures, motion path and per-site Z heights) in one file.

The S100B is part of a broader selective soldering portfolio — SO-300, SO-300B and SL-600 — so a factory can scale from a desktop station to an in-line process. For reference, the offline single-head SO-300B in the same family is documented at 300 × 250 mm maximum soldering area (customizable) and ±0.1 mm positioning accuracy; the S100B specifics for your joint geometry are confirmed at quotation.

Where it fits on the line

The S100B works as an offline, line-side or engineering station rather than a fixed conveyor position:

1. SMT front end prints, places and reflows the SMD side.
2. THT insertion places through-hole parts (Southern Machinery S3000/S3010A, S4000 and odd-form platforms).
3. Selective soldering joins the inserted THT joints — the full board or only the joints that cannot go through wave.
4. Post-solder inspection, cleaning and lead cutting follow.

For a factory already running wave soldering on high runners, the S100B complements it: volume goes through the wave line, while NPI, rework and low-volume variants use the desktop station. For a factory with no wave line, it can be the primary THT soldering resource during ramp-up.

Make it a recurring test

NPI volume grows and board variants multiply. Re-run the Fixture-Less Fit Test when engineering-change frequency rises or when prototype volume starts crowding your wave line — the threshold where a desktop station pays for itself moves as your mix shifts.

Your next step

Send your board dimensions, component list and batch sizes to jasonwu@smthelp.com or WhatsApp +86 136 0256 2576. The engineering team returns a configuration recommendation and a selective soldering process proposal tailored to your line.

FAQ

What is the S100B used for? A compact, fixture-less selective soldering station for THT components in high-mix, low-volume PCBA — rework, prototypes, small-batch production and boards that cannot be wave soldered.

How is selective soldering different from wave soldering? Wave soldering passes the whole board over a full-width wave (usually with pallets to protect areas). Selective soldering applies flux and solder only to programmed joints via a moving nozzle, leaving the rest of the PCB untouched.

Does the S100B need a fixture per PCB? It is designed as fixture-less with ultra-fast changeover — different models are handled by recalling stored programs rather than changing mechanical tooling. Confirm exact board-size limits with the supplier for your PCBs.

Which components can be selectively soldered? Connectors, relays, transformers, terminal blocks, electrolytic capacitors and other THT parts with defined joint positions; nozzle, alloy and flux are configured to the joint geometry.

How do I get configuration advice? Contact Southern Machinery with your board dimensions, component list and batch sizes. Catalogs are at file.autoinsertion.com and machine photos at ph.smthelp.com.

Jason Wu

Founder & CEO, Southern Machinery (Shenzhen Southern Machinery Sales and Service Co., Ltd.)

Email: jasonwu@smthelp.com / info@smthelp.com

WhatsApp: +86 13602562576

Catalog & manuals: file.autoinsertion.com | Machine photos: ph.smthelp.com

LinkedIn: linkedin.com/in/smtsupplier | YouTube: youtube.com/c/Smthelping