01Where Morewell Machines Fit in a PCB / SMT Line
In a typical PCB or mixed SMT/THT assembly line, there are five to six stages where Morewell equipment is used — before the main SMT line, between processes, and after final assembly. These stages are shown in the process flow below, with Morewell-relevant steps highlighted in blue.
Stencil Print
Solder paste on pads
SMA Dispense
Adhesive for bottom-side SMDs
Pick & Place
SMD placement
Reflow Oven
SMD solder joints
Underfill
Under BGA / CSP / Flip-chip
THT Insertion
Through-hole components
Selective Solder
THT joints — no wave risk
Conformal Coat
Board protection
Potting
Enclosure fill (if required)
★ = Steps where Morewell machines are typically deployed in a PCB / SMT assembly line
Not every board needs all five steps. A simple indoor consumer electronics board may only need selective soldering for its THT connectors. An outdoor industrial control board may need selective conformal coating plus potting. An automotive ECU with BGA processors needs underfill, conformal coating, and selective soldering. The right combination depends on your end-product's operating environment and reliability requirements.
This page explains each application clearly — what it does, what fails when it is done wrong, and what results our customers have seen after deploying Morewell automation. We do not cover solder paste printing, pick-and-place, or reflow ovens, because those are not Morewell's area and we believe in being precise about what we can actually help you with.
02Six Process Applications Explained
Below is a plain-language explanation of each PCB and SMT assembly process where Morewell machines are used — including what each process does, what failure looks like when it goes wrong, and how automation addresses it.
① Surface Mount Adhesive (SMA) Dispensing
When a PCB carries SMD components on its bottom side and will be processed through wave soldering, those components must be mechanically held in position during the wave. Surface mount adhesive (SMA) — a small dot of single-component epoxy — is dispensed onto the board before component placement. It cures during reflow and holds the component against the wave's turbulence.
② BGA & CSP Underfill Dispensing
BGA, CSP, and flip-chip packages connect to the PCB through solder balls underneath the package body — there are no visible leads. These hidden solder joints are highly susceptible to fatigue cracking caused by thermal cycling (the package and PCB expand at different rates) and by mechanical drop or vibration. Underfill is a low-viscosity epoxy dispensed along one or two sides of the package after reflow; it wicks underneath by capillary action and, once cured, encapsulates the solder balls and distributes mechanical stress across the entire package base rather than concentrating it at individual solder ball contacts.
③ Selective Conformal Coating
Conformal coating is a thin protective film — typically 25–250 μm thick — applied over a populated PCB to protect it from moisture, condensation, dust, salt spray, and chemical contamination. It is used whenever the product will operate in environments that expose the board to humidity cycling or contaminants: outdoor equipment, automotive electronics, industrial controls, agricultural machinery, marine instruments, and medical devices used outside a clean room. Without conformal coating, exposed PCBs in humid environments develop electrochemical migration between conductors — a gradual process that leads to current leakage, intermittent faults, and eventually board failure.
④ Selective Soldering — THT Components
Most modern PCBs are mixed-technology: the majority of components are SMD, but certain through-hole (THT) components — connectors, large capacitors, relays, transformers, fuse holders, and terminal blocks — are still used because of their mechanical strength or current-carrying requirements. After SMD components are placed and reflowed, THT components are inserted and need to be soldered. Wave soldering the entire board is often not viable because it exposes fine-pitch SMD components on the bottom side to excessive thermal stress. Selective soldering uses a precisely positioned mini-wave nozzle or laser to solder only the specified THT pad locations without heating the rest of the board.
⑤ PCB Assembly Potting & Encapsulation
Some PCB assemblies are potted — the assembled board is placed inside an enclosure which is then filled with a liquid compound that cures to a solid or semi-flexible state. Potting provides the highest level of protection available: total moisture exclusion (superior to conformal coating), vibration and shock isolation, electrical insulation between conductors, and optionally thermal conductivity between components and the enclosure wall. Typical PCB potting applications include outdoor LED driver boards, industrial power supplies, EV charger control modules, and communication equipment deployed in harsh environments where the board will never need to be repaired.
⑥ Glob Top & Dam-and-Fill Encapsulation
Glob top is a targeted encapsulation process used to protect bare semiconductor die and wire bonds that are mounted directly on a PCB without a standard IC package — a process called chip-on-board (COB). A dam material is first dispensed around the target area to create a retaining wall. A lower-viscosity fill material is then dispensed inside the dam to encapsulate the die and wire bonds completely. This is used in RFID tags, smart card modules, compact wearables, small medical sensors, and cost-optimized power electronics where standard packaging adds too much height or cost.
03PCB Assembly Process → Challenge → Morewell Machine
The table below maps each relevant PCB and SMT assembly process step to its core challenge and the Morewell machine that addresses it:
| Process Step | Line Position | Core Process Challenge | Morewell Machine |
|---|---|---|---|
| Surface Mount Adhesive (SMA) | Before wave soldering | Consistent dot volume; fast cycle time on sparse board layouts; no pad contamination | Dispensing Jet or needle valve |
| BGA / CSP Underfill | After reflow | Void-free wicking under package; viscosity control; heated dispense for fast capillary flow | Dispensing Heated needle valve dispenser |
| Selective Conformal Coating | Post-reflow / post-assembly | Selective coverage only; skip connectors & test points; 25–250 μm film; no masking | Dispensing Flat-jet or needle selective coating |
| THT Selective Soldering | After THT insertion | IPC Class 2/3 joint quality without wave thermal damage to adjacent SMDs | Soldering Automatic Soldering Machine |
| Thermal Interface Material (TIM) | Before heat sink mount | Full coverage; controlled thickness; abrasion-resistant valve for particle-filled TIM paste | Dispensing High-pressure piston dispenser |
| PCB Assembly Potting | Post-assembly / box-build | Void-free enclosure fill; consistent 2K mix ratio; no underfill or overfill | Potting Automatic Glue Potting Machine (2K) |
| Glob Top / Dam & Fill | Post-assembly (COB) | Dam height consistency; fill containment; no wire bond damage from pressure | Dispensing 2-step program: dam then fill |
04Technical Considerations for PCB Assembly
Material Types and Valve Selection
PCB assembly dispensing covers one of the widest viscosity ranges of any manufacturing industry — from ultra-low-viscosity underfill materials that rely on capillary action (under 5,000 cps) to thick dam materials and TIM pastes exceeding 200,000 cps. Using the wrong valve type for a material is the single most common cause of dispensing process problems in PCB assembly. Here are the main material categories and their key dispensing considerations:
Surface Mount Adhesive (SMA)
Applied as small dots (0.5–5 mg) under bottom-side SMDs. Needs consistent dot height for proper component seating. Thixotropic behavior means the material shear-thins under dispensing pressure and recovers quickly — good for sharp dot definition. Jet valve preferred for high-speed, sparse-layout boards.
Underfill Epoxy
Low-viscosity, heat-curable epoxy designed for capillary wicking under BGA/CSP packages. Highly temperature-sensitive — viscosity drops significantly when heated to 40–55°C, improving wicking speed dramatically. Heating the valve body is not optional for large or dense BGA packages — it is required for reliable void-free fill.
Conformal Coating
Four main types: acrylic (easiest to rework, most common), silicone (widest operating temperature range, -65°C to +200°C), polyurethane (best abrasion and chemical resistance), epoxy (hardest, best moisture and chemical barrier, not reworkable). Flat-jet nozzle for area coating; needle valve for fine edge work near exclusion zones.
Glob Top Dam Material
High-viscosity thixotropic epoxy dispensed as a retaining dam around bare die or sensitive wire-bonded areas. Must maintain sharp, near-vertical sidewalls without slumping before the fill material is applied. Requires a screw valve or positive-displacement valve; time/pressure valves do not provide enough control over this material class.
Potting Compound (1K or 2K)
Encapsulates complete PCB assemblies in a housing. 2K formulations require controlled A:B mix ratio — an off-ratio mix produces under-cured (soft, sticky) or over-hardened (brittle) material that fails under thermal cycling. Bottom-up fill prevents void entrapment by letting air escape ahead of the rising compound front.
Thermal Interface Material (TIM)
Applied between power components (CPUs, MOSFETs, power ICs) and heat sinks. Contains thermally conductive but abrasive filler particles — alumina, boron nitride, or silver. Standard needle and rotary valves wear rapidly with TIM. Requires high-pressure piston technology with stainless-steel or ceramic-lined wetted surfaces.
Selective Conformal Coating: Dispensing vs. Spray — An Honest Comparison
This is one of the most frequent questions we receive from PCB assembly manufacturers evaluating their coating process. Here is a straightforward breakdown:
The honest conclusion: for boards with three or more exclusion zones (a connector, a test point, a heat sink contact area), selective dispensing almost always delivers lower total cost per board than masking — once production reaches roughly 80–120 boards per day. Below that volume, the equipment investment may not be justified and selective spray with manual masking can be a practical bridge solution.
Selective Soldering: When It Is and Is Not the Right Choice
- Selective soldering is the right choice when your board has mixed SMT/THT construction, wave soldering would thermally stress fine-pitch SMD components on the wave-exposed side, and the number of THT joints exceeds what hand soldering can produce consistently — typically more than 6–8 joints per board at volumes above 100+ boards per day.
- Wave soldering remains more economical for primarily-THT boards with no sensitive SMD components on the bottom side, or for very high volume simple boards where the thermal exposure is acceptable.
- Hand soldering is appropriate for prototypes, very low volumes (under 50 boards per week), and boards with one or two THT joints that are not economical to set up in a selective solder program.
- Selective soldering adds the most value for boards where IPC-A-610 Class 3 solder joint quality is required and hand-solder consistency cannot reliably meet defect rate targets in production — automotive ECU, industrial safety controls, medical electronics.
IPC Standards Supported
Note: IPC certification is the manufacturer's responsibility. Morewell machines provide the process control, parameter logging, and repeatability that IPC and customer qualification audits call for.
SMA Jet Rate: 200 Hz
High-frequency jetting for surface mount adhesive — fast cycle time even on sparse layouts with widely spaced component positions
Positioning: ±0.1 mm
Gantry repeat accuracy — sufficient for SMA dots, underfill beads, glob top dam work, and conformal coating edge definition
Solder Temp: ±2°C
Selective soldering nozzle temperature control; N₂ blanket option for oxide-free joints; lead-free and Sn/Pb both supported
Coating: 25–250 μm
Conformal coating thickness range from light moisture protection to heavy build-up films for severe environment applications
Potting Mix: ±1%
2K A:B ratio accuracy for PCB encapsulation — ensures rated cure hardness and prevents under-cure or brittleness failures
100% Logged Per Board
All process parameters logged per board serial number as standard — supports IPC, IATF 16949, and customer traceability requirements
05Real-World Application Results
The following four examples are from actual Morewell customer deployments in PCB and SMT assembly. All company names are withheld under confidentiality agreements; all production figures are verified.
Mixed SMT/THT Industrial PLC Board — Selective Conformal Coating
An EMS company assembling industrial PLC control boards was applying acrylic conformal coating by manual spray gun. Each board had six multi-pin connectors, two screw terminal blocks, and four functional test points that required masking before every spray cycle. Masking and de-masking took an average of 4.5 minutes per board. Approximately 9% of boards per batch had coating bleed onto at least one connector pin — requiring solvent removal and re-spray before passing inspection. The customer's end-use specification required IPC-CC-830 compliance and a minimum dry film thickness of 50 μm across all coated areas.
A selective conformal coating dispensing machine was programmed with the board layout, defining coating zones and all exclusion areas (connectors, terminal blocks, test points). The machine applies acrylic coating in a single-pass flat-jet dispense at 80 mm/sec — no masking required. Center target film thickness: 75 μm. UV lamp verification is performed on the first board of each production batch. Parameter records are exported to the customer's MES by job number for IPC-CC-830 compliance documentation.
Smart Speaker Main Board — BGA Underfill Dispensing After Reflow
A PCBA manufacturer producing main boards for a smart speaker brand was experiencing a 1.8% field return rate related to BGA joint cracking at 12–18 months — a thermal cycling fatigue failure confirmed by cross-section analysis. The 12×12 mm BGA package had no underfill applied. A pilot run using manual syringe application showed incomplete fillet formation on three of the four package sides, indicating the underfill was not wicking fully under the package before gelation.
A heated needle valve dispensing machine was deployed to apply underfill in an L-shaped pattern on two adjacent sides of the BGA package. The valve body is heated to 45°C, reducing material viscosity from approximately 12,000 cps (room temperature) to approximately 4,000 cps — significantly improving wicking speed under the 576-ball array. A downstream cure oven (110°C / 30 min) completes the process. Void inspection by cross-section sampling is performed at 1 board per 200 production units.
ECU Power Board — Selective Soldering of 8 THT Connectors
An automotive electronics PCBA manufacturer was producing engine control unit (ECU) power boards with eight through-hole connectors per board alongside a dense SMD layout that included fine-pitch IC packages at 0.5 mm pitch. Wave soldering was ruled out due to thermal risk to SMD components. The customer's solder quality requirement was IPC-A-610 Class 3. Hand soldering was producing a 3.2% defect rate — predominantly cold joints and pin-to-pin bridges — generating significant scrap at the end-of-line AOI station. Average hand-soldering time: 68 seconds per board.
A selective automatic soldering machine with a nitrogen-blanketed mini-wave nozzle was programmed with the eight connector pad coordinates. Solder temperature: 255°C ±2°C (SAC305 lead-free). Dwell time: 3.2 seconds per connector. The nitrogen blanket prevents oxide formation and produces consistently bright, well-formed fillets meeting IPC Class 3 visual criteria. All solder parameters are logged per board serial number for the customer's IATF 16949 traceability file.
IP67 LED Driver Board — 2K Polyurethane Potting in Aluminum Housing
A manufacturer of outdoor LED driver boards was potting completed PCB assemblies inside aluminum housings using a two-component polyurethane compound. The drivers must pass IP67 water ingress testing and survive 100 thermal cycles between -30°C and 85°C (per customer specification). Manual potting was producing a 7% void rate at the base of the housing (detected by post-cure visual inspection through the vent hole) and a 4% underfill rate where compound did not reach the required height — both causing failures at IP67 and thermal cycle testing.
A 2K automatic glue potting machine with bottom-up fill nozzle and dynamic mixing head was deployed. Material fills from the lowest point in the housing upward, displacing air ahead of the rising compound front. A:B ratio metered at ±0.8% by volume. Post-fill height sensor gate checks every unit before advancing to cure — units outside the ±2 mm height window are flagged automatically. Cure schedule: 60°C / 90 minutes in a batch oven.
06Line Integration & Process Traceability
PCB assembly lines serving automotive, industrial, or medical markets require per-board process traceability and full MES integration. Morewell machines support this as standard:
SMEMA-Compatible Inline Conveyor
Standard SMEMA machine-to-machine interface — integrates directly into your existing in-line conveyor system without custom boards or separate handling stations
Per-Board Process Records
Dispense volume, coating path completion flag, solder temperature and dwell time, NG/OK result — logged per board serial number, exported as CSV, XML, or via REST API
Barcode & DMC Code Reading
Integrated barcode or Data Matrix Code scanner links all process data to the individual board traveller — supports customer-required genealogy records for IPC, automotive, and medical traceability
Real-Time NG Interlock
Any out-of-specification event (missed coating zone, solder temperature alarm, dispense short) stops the board at the station and prevents advancement — zero defective boards released downstream silently
SPC & Cpk Data Output
Process data streams support SPC software for Cpk monitoring on critical parameters — supports IPC, IATF 16949, and AS9100 process capability reporting requirements