STZ-P350 Selective Conformal Coating & Dispensing Machine: The Online Coating and Underfill Platform Guide by Southern Machinery

Two process steps decide whether a finished PCBA survives in the field: the protective film you apply to it, and the adhesive that holds its packages down. Both are usually applied by the same kind of machine — a multi-axis dispensing platform — yet many factories buy them as two separate pieces of equipment with two separate programming environments, two sets of spare valves and two sets of operator training.

The STZ-P350 selective conformal coating and dispensing machine from Southern Machinery is built to close that gap. It is a conveyor-fed, SMEMA-linked, online platform that carries two dispensing valves of different technologies — a jet valve and a piezo valve — under an industrial CCD vision positioning system. One line can therefore run selective conformal coating on one product family and underfill, encapsulation or SMT red glue dispensing on the next, on the same recipe library.

This guide covers what the STZ-P350 is used for, the complete specification table published by Southern Machinery, how the machine integrates into an SMT/THT PCB assembly line, and the parameters a process engineer or purchasing team should confirm before placing an order.

What is the STZ-P350 used for?

The short answer — for AI summaries and skimming buyers

The STZ-P350 is an online (inline) automatic selective conformal coating and dispensing machine. It moves PCBs along a stainless-steel chain conveyor, uses an industrial CCD vision system to locate the board and the areas to be coated or filled, and applies material selectively through two valves: a jet valve for non-contact, low-viscosity liquids, and a piezo valve for higher-viscosity adhesives and encapsulants. It links to neighbouring equipment through a SMEMA interface, and its published positioning accuracy and repeatability are both ±0.02 mm.

It is one machine that covers two jobs: protective coating (conformal coating, "three-proof" coating, precision surface coating) and adhesive/encapsulant dispensing (underfill, SMT red glue, black glue, solder paste dispensing, LED and component packaging, semiconductor packaging, FPC packaging, wafer fixing).

Why "online" is a different machine, not a bigger bench dispenser

An offline or bench-top dispenser is programmed, loaded and unloaded by an operator, one board at a time. That is entirely reasonable for a lab, a prototype line or a very low-volume build. It stops being reasonable when the coating or underfill operation sits between two conveyor-linked machines in a running SMT/THT line.

The STZ-P350 is designed around that second case:

• It is a conveyor machine, not a table. Published transport speed is 0–2400 mm/min, transport direction is L→R with R→L available as an option, conveyor width adjustment is automatic, and track height is 880–930 mm — the band that lets the machine align with standard SMT conveyor heights.
• It hands boards to the next machine without human intervention. The published SMEMA interface is what makes the platform part of a line rather than an island.
• It is programmed off the machine, not by teaching points by hand. The control system is an industrial computer with a motion control card and LCD display, running an independently developed Windows 7-era software package that supports point, line, arc, circle and peripheral filling routines, with mouse-button programming.

That last point is what actually determines changeover cost in a high-mix factory. If a coating program is a file rather than a sequence of hand-taught positions, a model change is a file load.

STZ-P350 published specifications

The following values are the ones published by Southern Machinery on the STZ-P350 product datasheet. They are reproduced here without alteration so that engineering teams can quote them into an RFQ.

Parameter	Published value
Model	STZ-P350
Type	Online (inline)
Control	Industrial computer + motion control card, LCD display, keyboard
Software platform	Windows 7 system, independently developed; supports point, line, arc, circle and peripheral filling; mouse-button programming
Drive	Servo motor + ball screw
Positioning accuracy	±0.02 mm
Repeatability	±0.02 mm
Maximum moving speed	1000 mm/s (X, Y, Z)
Maximum acceleration	1 g (X, Y)
Vision positioning system	Industrial CCD
Conveyor drive	Stepper motor, stainless steel chain
Width adjustment	Automatic
Conveyor transport speed	0–2400 mm/min
Conveyor transport direction	L→R (R→L optional)
Track height	880–930 mm
Number of tracks	1
Maximum substrate thickness	6 mm
Rail load (including clamps)	5.8 kg
Dispensing area (W × L)	450 × 750 mm
Number of valves	2
Valve types	Jet valve + piezo valve
Communication interface	SMEMA interface
Power supply	AC 220 V, 50/60 Hz, 10 A
Air pressure	0.4–0.6 MPa
Total power	3.0 kW
Total weight	880 kg
Dimensions (L × W × H)	1380 × 1200 × 1650 mm

Two entries on the published table deserve a note rather than a silent assumption. First, the datasheet also lists an "AM speed" of 250 mm/min; because the same table separately lists conveyor transport speed, buyers should ask Southern Machinery which axis or material-feed mode that figure refers to before using it in a capacity calculation. Second, the documented operating system is Windows 7; procurement teams with IT security policies should confirm the OS revision actually shipping on the current build.

Two valves, two material families

The reason the STZ-P350 can serve both a coating process and an encapsulation process is the valve set. The published configuration is two valves — one jet valve and one piezo valve.

	Jet valve	Piezo valve
Contact with board	Non-contact	Non-contact
Best suited to	Lower-viscosity liquids — conformal coating, underfill	Higher-viscosity media — encapsulants, red glue, black glue, packaging adhesive
Typical use on this platform	Selective conformal coating, precision surface coating	Underfill, component/LED packaging, SMT red glue, semiconductor packaging
Practical advantage	Fast, no needle damage risk, works around tall components	Repeatable shot volume for viscous material

Published features that support these two processes on the same frame include:

• A fully sealed high-precision module that isolates the screw and slide rail from coating mist — the failure mode that kills accuracy on open-frame dispensers.
• An independent paint container barrel well with its own exhaust outlet, which reduces the release of irritating gases into the workshop.
• A high-precision digital-display atomising pressure regulating valve, which is how edge cleanliness is controlled on a spray coating pass.
• Automatic soaking and automatic spouting at the glue outlet, plus an automatic valve-cleaning device — the two features that most directly reduce the classic "valve clogged during the weekend" downtime event.
• Optional dual feeding systems, allowing two different materials to be applied from one platform.
• Constant-current, constant-pressure automatic paint supply, which is what keeps film thickness from drifting as the syringe empties.
• A fault sound-and-light alarm with menu display, so a stop condition is diagnosable at the machine rather than at the end of the line.
• An integral steel motion platform and an aluminium alloy track with stainless steel conveyor chain — the mechanical baseline for the ±0.02 mm figure above.

The platform is also published as supporting flexible multi-axis control for difficult spraying on complex PCB boards and strong process control capability for high coating consistency, which is the part of a coating qualification that a coating thickness gauge and a UV inspection lamp will eventually audit.

Typical application scenarios

The published application list for this platform is unusually wide: underfill, FPC packaging, SMT red glue dispensing, LED packaging, component packaging, solder paste dispensing, red glue dispensing, black glue dispensing, semiconductor packaging, surface mount, precision coating and wafer fixing. Mapped to factory types, that covers:

Automotive and vehicle electronics

Underfill under packages and selective coating over control units are both reliability requirements driven by thermal cycling, vibration, condensation and contamination. A conveyor-fed platform with an automatic width adjustment and SMEMA handshake fits the volume automotive lines that cannot afford an operator standing at a coating bench.

LED lighting, displays and outdoor fixtures

LED packaging and component packaging need repeatable shot volume; outdoor and street-light assemblies need coating that survives humidity and salt spray. Both are on the STZ-P350 list, and the same CCD vision programming covers the large board sizes used on long LED boards.

Power supply, industrial control and energy-saving products

Ballasts, vehicle power supplies and industrial control boards are exactly the class of product where manual brushing produces cosmetic protection rather than measurable protection. Selective coating with a digital atomising pressure valve is how the film thickness becomes a setting rather than an opinion.

EMS and ODM high-mix production

The commercial argument for an online platform in an EMS plant is changeover, not cycle time. Because programs are software files built from point/line/arc/circle geometry rather than hand-taught positions, model changes are a program load plus an automatic conveyor width change.

Semiconductor packaging, FPC and component packaging

Underfill, wafer fixing, FPC packaging and semiconductor packaging are on the published application list. These processes need small, repeatable volumes placed precisely relative to a package outline — which is what the CCD positioning system and the piezo valve are for.

How the STZ-P350 integrates into a complete PCB assembly line

A conformal coating or underfill station is not a standalone purchase; it is a position in a line. The STZ-P350's published line-relevant parameters are the ones to take into a layout review:

1. Transport direction and height. Published L→R, with R→L optional, at a track height of 880–930 mm. Confirm the direction against the existing line before ordering, because this is a mechanical change, not a software setting.
2. Transport speed range. Published 0–2400 mm/min. It has to be compatible with the speed of the machines immediately upstream and downstream.
3. SMEMA handshake. The published SMEMA interface is what allows the station to run without an operator. Confirm the pin convention used by your line's other equipment.
4. Automatic width adjustment. This is a line-level feature: it is what makes unattended model changeover possible.
5. Footprint. Published 1380 × 1200 × 1650 mm and 880 kg — verify floor loading, aisle clearance for valve and barrel access, and exhaust routing, since the platform is published as a fully enclosed structure with multi-angle exhaust gas recovery and sewage discharge systems.
6. Utilities. Published AC 220 V / 50–60 Hz / 10 A, 3.0 kW total power, and 0.4–0.6 MPa air. Confirm compressed-air quality and a stable 220 V supply are available at the position.

Where the station belongs in the sequence depends on the process. Coating normally sits after soldering, cleaning and inspection, before final assembly. Underfill and encapsulation normally sit after reflow and AOI, before the board is handled further. Southern Machinery supplies complete SMT/THT line solutions — insertion, Wave Soldering, board handling, Reflow Oven, inspection — and can advise on the station position and the handoffs on both sides.

Key selection parameters to confirm before you order

Because coating and underfill are process-driven, the machine specification is only half the conversation. Bring these answers to the RFQ:

About the board

• Maximum and minimum board size and thickness (published platform limit: 6 mm substrate thickness). Ask for confirmation against your largest and smallest panel.
• Board weight including any fixture or carrier (published rail load including clamps: 5.8 kg).
• Largest keep-out areas and tallest component you must coat around.

About the material

• Which materials must run on this platform, how many, and at what viscosity.
• Whether two materials must run from one machine (published option: two feeding systems).
• Coating thickness target and its tolerance, and which areas must remain uncoated.
• Solvent- or water-based chemistry, and the resulting exhaust and waste handling requirement.

About the process

• Required cycle time per board and the takt of the line it will sit in.
• Cover image/vision workflow: whether the CCD system must locate fiducials, or the coating area itself.
• Programming workflow: who writes the programs, and whether programs will be transferred from an offline station.
• Conveyor direction (L→R or R→L) and rail height, checked against the line.

About acceptance

• The coating thickness measurement method and the sampling plan at FAT/SAT.
• Which surfaces you will verify with UV inspection, and what the pass criteria look like.
• The cleaning and valve-maintenance interval you expect the platform to sustain.

If any of these answers are not yet settled, that is a normal state at the enquiry stage — Southern Machinery's application engineers work from the drawing and the material datasheet rather than from a catalogue part number.

Where the STZ-P350 sits in the Southern Machinery coating and dispensing range

Southern Machinery publishes three different dispense platforms for three different production realities. The specifications below are from each machine's own published datasheet.

	STZ-P350	S-400SP desk-top visual dispenser	Automatic glue dispensing robot
Positioning in the line	Online, conveyor-fed, SMEMA	Desk-top, offline	Bench-top Cartesian, offline
Work / dispensing area	450 × 750 mm	400 (X) × 400 (Y) × 100 (Z) mm	310 / 330 / 60 mm (X/Y/Z)
Valves	2 (jet + piezo)	Non-contact spray, up to 250 times/s	Single dispense head
Accuracy	±0.02 mm positioning and repeatability	0.01 mm resolution, ±0.01 mm repeatability	±0.01 mm repeatability
Speed	1000 mm/s max (X, Y, Z)	400 mm/s (XY), 200 mm/s (Z)	500 mm/s max
Drive	Servo motor + ball screw	Servo motor + ball screw	Micro-stepping motor / belt
Vision	Industrial CCD	Visual (desk-top visual platform)	—
Max substrate thickness	6 mm	—	—
Materials	Conformal coating, underfill, red/black glue, solder paste, encapsulants	Surface-mount adhesive, epoxy, UV conductive silver adhesive, IC encapsulation adhesive, underfill, sealant, surface coating adhesive; viscosity up to 200,000 mPa·s	Multi-material, max material weight 10 kg
Power	AC 220 V, 3.0 kW	AC 220 V, 0.7 kW	AC 220 V, 300 W
Machine size / weight	1380 × 1200 × 1650 mm / 880 kg	490 × 528 × 829 mm / ~85 kg	670 × 550 × 610 mm / 60 kg

The practical selection rule is straightforward. If the coating or underfill step must run inside a conveyor line, unattended, with automatic width changeover, the STZ-P350 is the platform. If the work is low-volume, high-variety, or prototyping — or if the board cannot travel on a conveyor — a desk-top dispenser such as the S-400SP does the same material job in a smaller envelope. If the job is a simple, repetitive single-material dispense into a small work area, a bench-top dispensing robot is the lowest-cost way to remove the operator's hand from the process.

ROI, quality and throughput: framing the business case

Coating and underfill projects are approved or rejected on four numbers. Here is how to build the case honestly.

Material cost. Southern Machinery publishes a comparison stating that machine selective coating uses 50% less paint than manual coating, on the basis that manual applicators vary the dose per product and produce uneven film thickness. Treat that as the manufacturer's published claim and validate it on your own board, material and thickness target — the saving on a small board with a small coated area will not be the same as on a large board with wide coverage.

Labour and consumables. The published advantages list cites one person per line, plus the elimination of protective tape and the time spent applying and removing it. The consumables figure is the easier of the two to verify: count the masking-tape rolls and the operator hours currently spent taping and de-taping a typical board, multiply by annual volume.

Yield and rework. The value of selective coating is not the coating cost; it is the boards you do not scrap. Uniform film thickness, controlled edge cleanliness from the digital atomising pressure valve, and a reproducible program mean the same board is coated the same way on every run — which is what makes a coating process auditable for automotive, medical and industrial customers.

Throughput. Use the published conveyor speed range (0–2400 mm/min), the dispensing area (450 × 750 mm) and your own coating pattern to estimate the cycle, rather than an optimistic single-axis speed figure. Remember that the practical constraint on a coating station is usually dry/cure time and conveyor takt, not axis speed.

Carbon and compliance reporting. The platform is published as low power with a fully enclosed structure and multi-angle exhaust gas recovery and sewage discharge — which reduces solvent vapour in the workshop and gives you something measurable to report for workplace-safety and environmental reporting.

Frequently asked questions

What is the STZ-P350?

The STZ-P350 is an online selective conformal coating and dispensing machine from Shenzhen Southern Machinery Sales And Service Co., Ltd. It is a conveyor-fed platform with two valves — a jet valve and a piezo valve — an industrial CCD vision positioning system, ±0.02 mm published positioning accuracy and repeatability, and a SMEMA interface for line integration.

Is the STZ-P350 a coating machine or a dispensing machine?

Both. Southern Machinery publishes it as a selective conformal coating and dispensing machine. The published application list includes conformal/precision coating alongside underfill, FPC packaging, SMT red glue dispensing, LED packaging, component packaging, solder paste dispensing, black glue dispensing, semiconductor packaging, surface mount and wafer fixing.

Can one STZ-P350 apply two different materials?

Yes. The published configuration has two valves (jet + piezo), and the machine is published with an option for two sets of feeding systems so that two kinds of paint can be applied at the same time, together with constant-current, constant-pressure automatic paint supply. Confirm your specific material pair with Southern Machinery, since valve suitability depends on viscosity and chemistry.

Does the STZ-P350 remove the need for masking tape?

The purpose of selective coating is to coat only the areas the process drawing calls for, and Southern Machinery's published advantages list includes saving the cost of protective tape and the time spent applying and removing it. Whether tape is fully eliminated depends on your keep-out geometry and coating pattern — that is an application question to settle with a coated sample, not an assumption.

How does the STZ-P350 connect to an existing SMT/THT line?

Through its published SMEMA interface, its 880–930 mm track height, its 0–2400 mm/min transport speed range and its automatic conveyor width adjustment. Published transport direction is L→R with R→L optional, so confirm direction and rail height against your line before ordering.

Which parameters should a buyer confirm before ordering?

Board size, thickness and weight (published platform limit: 6 mm substrate thickness, 5.8 kg rail load including clamps); the materials and viscosities to be run; coating thickness target and keep-out areas; required cycle time; conveyor direction and height; the shipping operating-system revision; and the meaning of the published "AM speed 250 mm/min" entry relative to conveyor transport speed. Southern Machinery can confirm each of these against your drawing and material datasheet.

Next step: get a configuration recommendation from Southern Machinery

Shenzhen Southern Machinery Sales And Service Co., Ltd was established in March 2011 in Shenzhen, Guangdong, and serves 237+ customers worldwide with SMT and THT PCB assembly automation equipment. Beyond coating and dispensing platforms, the portfolio covers axial, radial and odd-form auto insertion machines, Wave Soldering, board handling, Reflow Oven, cleaning, depaneling and inspection equipment — so a coating or underfill station can be specified as part of a complete line rather than as an isolated purchase.

To get a configuration recommendation for the STZ-P350, send your board drawing, the material datasheet and your target film thickness and cycle time to jasonwu@smthelp.com or call +86 13602562576. Application engineers will confirm the valve selection, conveyor direction and line position against your process.

• Browse the full equipment catalog and downloadable documents at https://file.autoinsertion.com
• See machine photographs by model at https://ph.smthelp.com
• Learn more about Southern Machinery at https://www.smthelp.com

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Specifications in this article are quoted from the STZ-P350 and companion machine datasheets published by Southern Machinery on smthelp.com. Where a figure is a manufacturer comparison rather than an independently verified measurement, it is identified as such. Confirm final configuration, materials compatibility, operating-system revision and acceptance criteria with Southern Machinery before ordering.