Reflow Soldering Oven Cases: Protection for Heating Zones & Conveyor Chains

Moving a reflow soldering oven or rebuilding a line usually fails at the step that looks easiest: lift the heating-zone cover, pull the quartz heater tubes, unbolt the conveyor rails, and hand the lot to a freight forwarder. At the new site the crew finds hairline cracks where three quartz tubes touched each other, a K-type thermocouple whose armoured sheath has been bent into a right angle, two three-metre rails bowed along their whole length, and chain pins rusted a dull red. When the oven is reassembled the profile refuses to line up, and the defect rate climbs steeply. The problem was never the installation; it was the packing.

The protection logic for reflow oven parts is not "cool it down and strap it tight" but "assign each part its own load path and moisture path according to its failure mode." Quartz parts accept elastic support only and never a point contact. Temperature-sensing parts may be coiled only within their permitted bend radius. Rails must be supported at many points in the posture where self-weight causes least bow. Flux residue must be cleaned to neutral before the case closes, or it will corrode the liner and the metal parts from inside. JUNZHIJIA works zone by zone, building a part list from the oven, then fixing the support method, moisture class and cleaning boundary for each item, and only then selecting shell structure and sealing class.

Table of Contents

• Brittle Fracture Control for Quartz Heater Tubes and Ceramic Elements
• Preserving Thermocouple Accuracy and Compensating Leads
• Conveyor Rail Straightness and Chain Pin Anti-Bend Constraints
• Flux Residue Attack on Case Liners and the Cleaning Boundary
• Dynamic Balance Protection for Heater-Zone Ducts and Blower Impellers
• Anti-Crush Support for Zone Baffles and Insulation Blanket
• Rust-Proof Packing for Chain Tensioners and Sprocket Teeth
• Draining and Freeze Protection for Cooling-Zone Water Coils
• Cleanliness Retention for Nitrogen Lines and Mass Flow Meters
• ESD Packing for Temperature Controllers and Solid-State Relays
• Secondary Contamination Control on Chamber Liners and Rail Faces
• Arrival Acceptance and Profile Re-Test for Reflow Oven Parts
• Frequently Asked Questions FAQ
• Conclusion and Related Reading

Brittle Fracture Control for Quartz Heater Tubes and Ceramic Elements

Reflow oven heating zones use three families of element: quartz infrared tubes, halogen lamps with a tungsten filament inside a quartz envelope, and ceramic-bodied resistance elements. All three are brittle, though not equally so.

Quartz glass has a thermal expansion coefficient of only about 5.5x10^-7 per kelvin, which is exactly why it was chosen. It can be taken to 400 degrees Celsius and quenched without cracking. Because that failure path is closed, every remaining failure comes from mechanical stress: transverse rupture strength is only 50 to 70 MPa, and the material barely yields, so once local stress passes the threshold it cracks immediately. Typical tube diameters run from 8 to 16 mm with wall thickness of 1.0 to 1.5 mm, and halogen envelopes can be as thin as 0.8 mm.

The clamping rule reduces to one sentence: support only near the ceramic end caps, never at mid-length. The worst loading for a quartz tube is not bending alone but two hard supports with a point load between them, which raises local wall stress until a crack starts. Where the liner can only offer a flat bed, it is better to let the tube rest freely in a soft foam channel than to "hold" it with a rigid divider.

Halogen lamps need two extra precautions. The tungsten filament is supported by molybdenum foil sealed into the quartz at each end, and that seal is far weaker than the tube body, so it is the preferred fracture site for any impact; both ends therefore need elastic support such as a silicone boot or EVA ring rather than a metal clamp. The reflective coating, usually gold or ceramic, creates a hot spot once scratched, so the tube must never rub against a hard material and the liner surface should be a lint-free soft grade. Comparable isolation practice for brittle glass and ceramic items is set out in precision instrument compartment protection.

Preserving Thermocouple Accuracy and Compensating Leads

Profile accuracy depends directly on the thermocouples. K-type junctions, nickel-chromium against nickel-silicon, carry a tolerance of plus or minus 1.1 degrees Celsius or 0.4 percent of reading, whichever is greater, over 0 to 400 degrees, with N-type slightly better. Three failure modes matter in transit.

Over-bent armoured sheath: armoured thermocouples are 1.0 to 3.0 mm in diameter and usually specify a minimum bend radius of five times the diameter, so a 2 mm sheath needs 10 mm. Folding one into a right angle to fit a corner loads the magnesium oxide insulation and the wires, and the reading drifts afterwards.

Deformed hot junction: a welded bead is only 0.3 to 0.8 mm across. Flattening or stretching it changes the thermal mass and shifts the whole dynamic response.

Compensating lead polarity and shielding: K-type compensating leads are polarised, and reversing them introduces an error equal to the temperature difference itself. Running them alongside power cable couples the heater PWM switching straight into a millivolt signal.

Pack accordingly. Coil the armoured sheath at a diameter of at least 200 mm and never fold it sharply. Cap the terminals so no pin is exposed. Pack the compensating lead separately from the junction and keep both out of the same chamber as power cable, contactors or transformers. Where a cold-junction module is supplied separately, give it its own pocket and antistatic treatment.

Insertion-depth marking matters more than most people expect. A thermocouple that is not inserted deep enough reads low because heat conducts along the sheath. Mark the original insertion depth on the sheath before packing, using a high-temperature marker or a fine scribe line, and reset to that line on arrival instead of judging by eye. Errors in the whole chain, junction to compensating lead to input module, add up, and any drift shifts the profile, which in SMT shows up as poor wetting or tombstoning.

Accuracy retention does not mean the thermocouple must be error-free on arrival. What matters is reproducibility: the same junction reads the same value under the same conditions, and the relationship between zones is unchanged. Comparison against a reference thermocouple in one stable source is therefore the right test, not absolute calibration.

Conveyor Rail Straightness and Chain Pin Anti-Bend Constraints

Reflow conveyors normally use chain on rails, with rails 2 to 4 m long, mostly aluminium extrusion with a stainless or hardened running face. Straightness is typically held to 0.3 to 0.5 mm per metre, with total deviation under 1.5 mm. That looks undemanding, but it is maintained in service by short support spans rather than by rail stiffness.

The classic transit defect is self-weight sag combined with too few supports. A three-metre rail on two end supports can sag several millimetres at mid-span; most of that is elastic, but prolonged vibration converts part of it to permanent set. Two further defects appear directly: local kinks where a forklift or case wall struck an end, and bent chain pins, commonly 2 to 4 mm in diameter, after lateral squeezing.

Posture is the commonly missed variable. Laying a rail flat feels safer because the centre of gravity is low, but for a slender profile the flat direction is often the one with the lowest second moment of area, giving the worst sag. Where the section allows it, stand the rail so that bending occurs about the strong axis, which for a rectangular extrusion means the long side vertical. For an asymmetric profile, work along the principal axis. That decision belongs in a simple simply-supported beam estimate at the packing design stage, not in the loader's judgement.

Flux Residue Attack on Case Liners and the Cleaning Boundary

A reflow oven is a flux-residue environment. The chamber walls, blower impellers, rails and chain links all carry a film ranging from pale yellow to dark brown. At operating temperature that film is a stable glassy or resinous deposit. Once it enters a cool, humid packing case, it behaves completely differently.

Flux residue falls into three chemical families, and each attacks packing materials differently.

The central conclusion is that water-soluble flux residue containing halide activators must never ship with the parts. At pH 2 in a case above 70 percent relative humidity, it will pit an aluminium baffle, rust steel fasteners and embrittle paper labels and corrugated inserts within weeks. Those corrosion products then act as abrasive particles and contaminate rail faces and optical parts.

Judge the cleaning boundary by surface resistivity or ionic contamination, not by appearance. In the shop, a simple pH check works: press deionised-water-dampened pH paper against the cleaned surface for one minute, and if the reading is below 5.5, acid residue is still present and the part must be cleaned again. Bag cleaned parts in PE immediately so they cannot re-adsorb flux aerosol in the shop.

Liner choice follows from the same logic. A case that will hold parts long exposed to flux atmosphere should not use ordinary EPE foam, which absorbs moisture and resists acid poorly. IXPE and EVA perform better, and their closed cells also resist liquid ingress. Where a customer insists on shipping parts in their service condition with trace residue, add an aluminium composite film between the part and the liner. Broader limits for dust-free packing appear in cleanroom equipment dust-free packing requirements.

Dynamic Balance Protection for Heater-Zone Ducts and Blower Impellers

Forced-convection reflow ovens use a circulation blower in each zone, with impeller diameters from 200 to 450 mm and balance grades usually G6.3, or G2.5 on premium machines. That grade is measured on a clean impeller, so any deposit, deformation or shaft-end load destroys it.

Three risks apply at the packing stage. Blade deformation is easy: blades are pressed or riveted sheet 0.8 to 1.5 mm thick, and a lateral knock shifts their angle, where one degree of deviation creates a substantial unbalance at 3000 rpm. Shaft-end loading is the second: the impeller sits directly on the blower shaft, so resting the assembly on the impeller and letting it carry the weight bends the shaft and alters bearing preload. Deposit shedding is the third: after service the impeller carries a flux coking layer, and vibration shakes part of it loose, creating a fresh unbalance.

Impellers must therefore be supported at the bearing housing and located on the shaft bore, never on blades or disc. Build a saddle matching the bearing housing diameter so the blower sits in its service posture with the shaft horizontal and the impeller in free air. Where the impeller ships separately, locate it on a mandrel through its bore and leave at least 20 mm of clearance all round. Ducts, flow guides and chamber liners are thin sheet parts and should be bedded flat on multiple supports, since standing them on edge squeezes the face into waves.

Where a blower assembly will be rebuilt on site, mark pairing references on non-mating faces: the relative angle of impeller to shaft, and the orientation of impeller to housing. These are hard to confirm after assembly, and fitting one the wrong way round produces uneven airflow and poorer temperature uniformity.

Anti-Crush Support for Zone Baffles and Insulation Blanket

Multi-zone ovens separate adjacent zones with baffles and insulation blanket. Baffles are commonly 0.8 to 2.0 mm stainless or aluminium sheet, and the insulation is aluminosilicate fibre blanket or ceramic fibre board at 96 to 128 kg per cubic metre.

Both parts fail by crushing. A baffle pressed by a heavy item takes a permanent wave, and once refitted the gap against its neighbour opens, letting heat leak from the upstream zone to the downstream one. The profile then shows an abnormal step at the zone boundary. Insulation crushed beyond roughly 15 percent loses fibre structure and resilience; the density rises, the thermal conductivity changes and performance falls. Crushed blanket also delaminates and sheds fibre, which drifts into the chamber and contaminates product.

Packing requirements are unambiguous: baffles take distributed face support only and no concentrated load; blanket stays free, with compression under 10 percent and full moisture protection.

Moisture protection for blanket is often skipped. Aluminosilicate fibre is non-combustible but highly hygroscopic, so a damp blanket gains weight, loses insulation performance and can leach trace soluble species. Vacuum or partial-vacuum bag it in PE with desiccant inside. On opening, if the fibre is caked or smells, dry it at 120 degrees Celsius for two hours before use. Fibre that has become brittle and dusty has already been overheated or damp for too long and should be replaced rather than patched.

Pack baffles and blanket in separate chambers. A hard baffle edge and soft blanket in one case damage each other: the edge cuts the fibre and the fibre dust enters the baffle gaps and interferes with reassembly. Where they must share a case, separate them with a rigid partition at least 5 mm thick, itself supported at multiple points.

Rust-Proof Packing for Chain Tensioners and Sprocket Teeth

Chain tensioners and sprockets combine a precision tooth form with a lubrication-dependent life. Sprockets are usually case-hardened steel at HRC 55 to 60, but once the hardened layer rusts the tooth flank pits, and pits are stress raisers that accelerate roller wear. The cumulative pitch error of the whole chain then grows, and boards skew or jam in the oven.

Three requirements follow. Keep the tooth flank off the foam, because some foams release mildly acidic species when damp and will pit a steel flank on contact; apply VCI film to the flank first, then locate it in a neutral liner. Release the tension spring, since it lives compressed in service and will stress-relax if left that way, giving insufficient tension on arrival; fit a stop or follow the manual to return it near free length. Add desiccant and a humidity indicator card inside the case, at about 20 g per cubic metre of free volume with 40, 50 and 60 percent thresholds, increasing the quantity by half on humid routes.

Rust prevention and moisture control are different jobs. VCI film suppresses electrochemical corrosion at the metal surface, while desiccant lowers relative humidity and prevents condensation; neither replaces the other. On sea freight both are mandatory, and the desiccant must sit where air can circulate rather than being fully wrapped in foam, because a buried bag presents little absorbing area.

Sprockets, tensioners and idlers form one functional group and are best packed and counted as a group. There are usually at least two of each per chain, and one missing part delays the whole installation. Grooving the liner by group and numbering within the group is the cheapest way to keep the count honest.

Draining and Freeze Protection for Cooling-Zone Water Coils

Cooling zones are either water-cooled, using copper or stainless coils fed from a chiller, or compressor-cooled with their own refrigerant circuit. Water-cooled coils carry the highest freeze risk in winter transit.

Water reaches its maximum density at 4 degrees Celsius and expands on freezing, growing about 9 percent in volume and generating expansion pressures above 100 MPa, enough to burst copper tube. Typical damage is a bulged wall, a cracked braze or a distorted sealing face. It usually appears during the post-installation pressure test, and repair means cutting out a whole coil section.

Freeze protection runs in three steps: drain, cap, label. Drain by blowing dry compressed air at 0.4 to 0.6 MPa from the inlet until no mist appears at the outlet, orienting the coil so water can run out, and blowing each branch of a multi-branch coil separately. Cap every connection immediately after draining and fit a tamper label. Where a dead leg genuinely cannot be drained, inject a small amount of food-grade propylene glycol, which is compatible with copper and stainless, while remembering that glycol does not replace draining: pouring it into a coil still full of water merely dilutes the water and traps it. Finally, label the case clearly to state that the circuit is drained or contains glycol, and that it must be flushed before refilling.

Where the cooling zone includes a finned heat exchanger, treat it as a separate risk. Fins are only 0.1 to 0.15 mm thick and bend on contact. Fit a rigid frame around them, never apply tape directly to fins, and never place them fin-side down. Once fins are bent by more than a third of the fin pitch, heat transfer drops noticeably and repair on site is impractical, so the packing cost is trivial compared with replacement.

Cleanliness Retention for Nitrogen Lines and Mass Flow Meters

A nitrogen reflow oven uses stainless tube, a pressure regulator, filters and mass flow meters. Internal surface roughness is often specified at Ra 0.4 micrometre or better, and an MFC holding plus or minus 1 percent of full scale is highly sensitive to particulate contamination.

Cleanliness depends on capping everything, all the way through. Cap both ends of every tube immediately after removal, using stainless or clean-coated plastic plugs rather than plain rubber stoppers, whose plasticisers leach and create organic contamination. Tube left on the shop floor draws in air carrying flux aerosol, which lays down an invisible organic film that slowly releases into the nitrogen after reassembly and contaminates product surfaces.

MFCs need more. Their internal capillaries and sensors shift calibration under mechanical shock, so give each unit its own pocket with no metal neighbours, protect the sealing face or O-ring groove with a cover so it cannot be scratched, hold case humidity below 60 percent relative humidity to protect the electronics, and purge with dry nitrogen before packing if the unit has been in service.

Filter elements, usually rated 0.01 to 0.1 micrometre, are contaminated after service and should travel as a consumable, separately packed and tagged for replacement, not installed in the line. A used filter shaken in transit releases particles and becomes a contamination source itself.

Package the whole gas system by segment number and flow arrow. Mark each tube with its segment and flow direction, and use different coloured caps for inlet and outlet. That discipline cuts wiring errors during reassembly, and a wiring error in this system means a whole atmosphere run is wasted.

ESD Packing for Temperature Controllers and Solid-State Relays

The electrical side of a reflow oven includes PID controllers, solid-state relays, thermocouple input modules and communication modules. Two damage paths dominate in transit: electrostatic discharge and moisture.

ESD works like this. In dry conditions, plastic foam rubbing against a case wall can generate several thousand volts, and an operator touching a module terminal on opening releases that charge through the input stage, puncturing a MOSFET gate or a CMOS protection structure. The damage is latent, reads normal at dispatch, and appears as zero drift or a dead channel after tens of hours of operation.

Where the case shell is insulating plastic, fit a grounding terminal or choose a conductive-filled shell so that staff can discharge before touching parts. That single detail is extremely valuable in dry regions. Modules are also rated for mechanical shock, often as 15 g half-sine for 11 ms, so the foam cushion stroke must keep peak acceleration below that threshold in a one metre drop. General limits for static-sensitive assemblies are covered in antistatic case selection and grounding.

Secondary Contamination Control on Chamber Liners and Rail Faces

Secondary contamination is what happens between cleaning and closing the case. Reflow shop air carries flux aerosol, solder spheres, glass fibre fragments and dust, all of which settle on cleaned chamber liners and rail faces.

Control it by shortening the exposure window and by creating a clean zone. Move cleaned parts straight into a clean area, which may be a soft-wall booth or a positive-pressure packing room, and keep exposure under thirty minutes. Clean the floor and benches daily, require shoe changes and gloves, and ban grinding, cutting and air tools inside. Pack parts inside the clean area, bag them, then move them to the case-loading station. Keep the loading station physically separated from production so that forklifts and logistics traffic do not raise dust.

Chamber liners are usually stainless and carry a flux coking layer. Two cleaning cautions apply. Do not use wire brushes or aggressive abrasives, because scratches become anchor points for the next coking cycle and make later cleaning harder. Use neutral or mildly alkaline chemistry and avoid chlorine-containing cleaners, since chloride residue reacts with chromium in the stainless at high temperature and causes intergranular corrosion.

Rail faces are the other sensitive surface, because their accuracy governs how smoothly boards transfer. Any solid particle left on a rail face is rolled over by the chain rollers and forms an indentation. Cover rail faces with a residue-free PE protective film immediately after cleaning, and keep that film intact while packing. Further limits on contamination and moisture in transit for electronic assemblies appear in PCB and electronic assembly transport protection, and comparable small-part protection on the placement side is covered in SMT feeder nozzle protection design.

Arrival Acceptance and Profile Re-Test for Reflow Oven Parts

Arrival inspection exists to separate transport liability from installation liability, and to feed the findings into the next packing revision. Work in three stages.

Stage one, appearance and packing condition, within thirty minutes of opening. Check the case for distortion, the seal for displacement, the humidity card for colour change and the shock indicator for triggering, and photograph every part with the case number and timestamp in frame. If a flux smell is present inside the case, cleaning was incomplete or parts shipped with residue, and a second cleaning cycle should start at once.

Stage two, static accuracy. Measure rail straightness on a granite table with a dial gauge at no fewer than two points per metre. Sample chain pin diameter and pitch with a vernier. Inspect quartz tubes visually and under magnification for wall cracks and end-seal damage. Compare thermocouples against a reference in one stable source.

Stage three, function. Run the conveyor unloaded for thirty minutes and watch for chain crawl, noise and skew. Then run a full profile at production speed and board thickness. The profile is the final criterion: an abnormal step at a zone boundary, or a shift beyond plus or minus 3 degrees Celsius, sends you back to stage two to check baffle distortion, crushed blanket and the measuring chain.

A packing record should carry the case number, packing date, packer, zone assignment, part list with serial numbers, cleaning method and post-clean pH reading, desiccant and indicator card batches, shock indicator threshold, and transport mode with expected duration. That record becomes the baseline for the next relocation. If one class of part is damaged twice in a row, the packing method needs changing rather than the luck.

Frequently Asked Questions FAQ

Q: Why do quartz heater tubes break more easily in transit than metal ones?

A: Because they fail without any plastic stage. A metal tube bends on impact and absorbs energy, and an operator can usually see the deformation. Quartz glass has almost no elastic range, so once stress passes its transverse rupture strength of roughly 50 to 70 MPa it cracks immediately, and the crack often starts internally or at the end seal where it is not visible at first glance. Wall thickness of only 1.0 to 1.5 mm makes this worse, because a mid-length load point raises local stress very quickly. The packing principle therefore differs completely from metal parts: use V-groove pockets for distributed face contact, place supports near the ceramic end caps, and allow soft material to wrap the mid-section rather than letting a rigid divider clamp it. Before packing, rotate every tube under strong light and check the wall for whitening or hairlines and the end seal for nicks, admitting only sound tubes to the pockets. Never stack heavy items on top of the case, and keep hard parts out of the same chamber.

Q: How is thermocouple accuracy verified after transport?

A: Work through appearance, continuity and comparison. For appearance, check the armoured sheath for kinks, confirm the minimum bend radius still exceeds five times the diameter, look for a flattened or stretched hot junction, and inspect the terminals for oxidation. For electrical checks, measure circuit continuity with a multimeter and insulation resistance with a 500 V DC megohmmeter, where 100 megohm or more is the usual requirement; a low reading means the magnesium oxide inside has absorbed moisture and the sheath needs two hours at 200 degrees Celsius before re-testing. For comparison, insert the suspect thermocouple and a reference thermocouple into the same stable source, such as a water bath, dry block or salt bath, and read the difference at 100, 200 and 300 degrees Celsius after five minutes of stabilisation at each point. The deviation should lie inside the tolerance for that letter designation, which for K-type at 300 degrees is plus or minus 1.1 degrees or 0.4 percent, whichever is greater. Absolute calibration is not the point; reproducibility of one junction over time, and the relative relationship between zones, is what protects the process.

Q: How much rail bow is acceptable before straightening or replacement?

A: Judge by straightness rather than by eye. The engineering requirement is usually 0.3 to 0.5 mm per metre with total deviation under 1.5 mm. Measure on a granite table or against a straight edge with feeler gauges or a dial indicator, at no fewer than two points per metre, and always include points within 200 mm of each end. If a single reading falls between 0.5 and 1.0 mm per metre, the rail can be straightened by applying distributed reverse load at several points, then left to settle for 24 hours and re-measured. Above 1.0 mm per metre, or where a straight edge shows light gaps concentrated over a very short length, the rail has taken a plastic kink; straightening leaves residual stress that slowly relaxes through heat cycles after refitting, so replace the rail. Straightening must never be local: apply load across the full length and check the same cross-section in two perpendicular directions, otherwise the rail twists while appearing to straighten.

Q: Which cleaner should be used for flux residue inside the oven?

A: Match the cleaner to the flux family rather than using one solvent for everything. Rosin-based RA and RMA residue is largely resin and rosin, best removed with isopropyl alcohol or a dedicated rosin cleaner by wiping or ultrasonics, followed by a deionised water rinse to carry away solvent residue. No-clean residue is lighter but still contains activators, so isopropyl alcohol plus a deionised water rinse works, concentrating on solder-side surfaces and rail faces. Water-soluble OA residue contains organic acid or halide activators, with room-temperature extract pH as low as 2.0 to 3.5, and must be rinsed thoroughly with deionised water and a neutral cleaner, at least twice, with the final rinse water below 10 microsiemens per centimetre. Whatever the family, dry immediately afterwards and verify on site with pH paper: press deionised-water-dampened paper against the surface for one minute, and a reading below 5.5 means clean again. Chlorine-containing cleaners are prohibited, because chloride residue causes intergranular corrosion of the stainless chamber at service temperature.

Q: How is blower impeller balance preserved before and after transport?

A: Three stages. Before packing, clear the flux coking from the impeller, because deposits shed under vibration and create fresh unbalance, then re-check balance and record the residual unbalance. During packing, support the assembly at the bearing housing and locate it on the shaft bore; never let blades or the disc carry weight, and never use the impeller as a packing block on the case floor. Where the impeller ships apart from the blower, fix it on a mandrel through its bore, leave at least 20 mm of clearance all round, and keep it out of any pocket containing hard parts. On arrival, first check blades visually for angle deviation and loose rivets, then turn the shaft by hand and listen for noise, and finally run the blower unloaded and measure vibration velocity. If vibration is more than 30 percent above the pre-move baseline, remove the impeller and rebalance it. Mechanical blade adjustment is only for slight deformation, and each blade angle must be measured rather than judged by feel.

Q: What happens when zone baffles and insulation blanket are crushed?

A: The consequence is degraded thermal control, not merely cosmetic damage. A baffle that has taken a permanent wave leaves a gap against its neighbour when refitted, so heat leaks from the upstream zone into the downstream one. The profile then shows an abnormal step at the zone boundary, where the affected zone runs below set point while the adjacent zone runs hot, and boards passing through receive less heat input than the process requires, producing poor wetting and cold joints. Insulation blanket compressed beyond roughly 15 percent loses fibre structure, gains density and changes thermal conductivity, so insulation performance drops. Crushed blanket also delaminates and sheds fibre, and the fibre that drifts into the chamber contaminates product surfaces and causes false calls in optical inspection. Neither defect is repairable on site: a straightened baffle springs back, and crushed blanket cannot be restored to loft. The answer is to prevent crushing at the packing stage, with distributed face support for baffles, no stacking load above them, and blanket kept free at 10 percent compression or less inside sealed moisture-barrier bags.

Q: How are cooling-zone water coils protected against freezing in winter transit?

A: Drain, cap, label, in that order. To drain, disconnect the inlet and outlet, blow dry compressed air at 0.4 to 0.6 MPa from the inlet side until no mist appears at the outlet, and orient the coil so that water can run out; blow each branch of a multi-branch coil individually rather than only the main path. To cap, close every connection immediately with a plug and fit a tamper label, and where a dead leg cannot be fully drained, inject a small amount of food-grade propylene glycol, which is compatible with copper and stainless. Remember that glycol does not replace draining: if the coil still holds water, injecting glycol merely dilutes it and traps it. To label, mark the case clearly to state that the circuit is drained or charged with glycol and that it must be flushed before refilling. Where the cooling zone includes a finned heat exchanger, remember that fins are only 0.1 to 0.15 mm thick, so fit a rigid frame and never place them fin-side down; fins bent beyond a third of the pitch should be replaced.

Q: How should the reflow profile be re-tested on arrival, and what are the criteria?

A: Unloaded warm-up, steady-state run, then data comparison. Run the conveyor unloaded for thirty minutes, watch for crawl, noise and skew, and confirm the rail straightness re-check passed. Then set each zone to its process value and wait until measured values stable within 2 degrees Celsius of set point for fifteen minutes. Run a full profile at normal production speed and board thickness with a profiler, using at least six measurement points on both board sides. Apply three criteria: the soak temperature in each zone within 3 degrees Celsius of the pre-move baseline, peak temperature and time above liquidus inside the process window, and no abnormal step in the ramp or cooling slope, where a step at a zone boundary points first to baffle distortion or crushed insulation. Always run the profile in a warm oven after preheating, since data taken cold has no comparative value, and repeat the run twice to rule out an outlier. The profiler itself must be within its calibration period, or instrument error and oven error cannot be separated.

Conclusion and Related Reading

Reflow oven transport protection translates a process window into packing constraints: quartz rupture limits, thermocouple bend radii, rail straightness, impeller balance and flux pH become pocket sizes, supports, cleaning criteria and sealing classes. JUNZHIJIA builds custom liner and case solutions.

Related Reading

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