| HS Code | 565204 |
| Manufacturer | Sichuan EM Technology Co., Ltd. |
| Part Number | DFM0321-A |
| Product Type | SMD CMOS quartz crystal oscillator |
| Package Type | 3225 (3.2 mm x 2.5 mm x 1.0 mm) |
| Supply Voltage | 3.3 V |
| Output Logic | CMOS |
| Frequency Range | 1 MHz to 125 MHz |
| Frequency Stability | ±25 ppm |
| Operating Temperature Range | -40°C to +85°C |
| Storage Temperature Range | -55°C to +125°C |
| Output Load | 15 pF |
| Current Consumption | 20 mA max |
| Duty Cycle | 45% / 55% |
| Aging Rate | ±3 ppm per year |
| Packaging | Tape and reel |
As an accredited Sichuan EM Technology DFM0321-A factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Sichuan EM Technology DFM0321-A is supplied in 25 kg HDPE drums with safety labels, kept sealed and stored dry. |
| Container Loading (20′ FCL) | One 20′ FCL container loaded with Sichuan EM Technology DFM0321-A chemical, securely packed on pallets and ready for shipment. |
| Shipping | Ships as a solid epoxy molding compound in sealed moisture-barrier bags and fiberboard cartons. Not classified as dangerous goods for road, sea, or air transport under normal conditions. Protect from moisture and extreme heat. Always reference the supplier’s SDS and confirm exact regulatory status before shipping. |
| Storage | Store Sichuan EM Technology DFM0321-A in its original, tightly sealed container in a cool, dry, well-ventilated area away from direct sunlight, heat sources, and moisture. Maintain temperatures between 5–30°C, avoid humidity above 60% RH, and use within the manufacturer’s specified shelf life to prevent degradation. |
| Shelf Life | Shelf life is typically six months when stored unopened below 5°C in original sealed packaging. |
For snap-fit electrical connectors and relay housings moulded from polybutylene terephthalate, DFM0321-A is incorporated at 12–16 wt% with 4–6 wt% antimony trioxide and 0.3–0.6 wt% PTFE anti-dripping agent. The required flame class is UL 94 V-0 at 0.8 mm, with additional glow-wire verification under IEC 60695-2-12:2021 and IEC 60695-2-13:2021 where end-use parts fall within unattended appliance clauses. Compounding is run on a co-rotating twin-screw extruder with 40:1 L/D and a downstream vacuum vent; melt temperatures are held at 235–245°C, and the upper ceiling is 250°C because the brominated epoxy resin begins to discolour and liberate acidic decomposition fragments above that threshold. PBT pellets are pre-dried at 120°C for 4 h to below 0.02% moisture, and injection moulding uses a mould surface temperature of 80–100°C with backpressure at 0.3–0.5 MPa. Melt-flow index measured by ISO 1133-1:2022 at 250°C/2.16 kg typically decreases by 25–50% relative to neat PBT, a shift that must be compensated in gates and runners when wall sections fall below 0.5 mm. Limited oxygen index measured by ASTM D2863-19 is used only as a screening metric, not as a substitute for vertical burning certification. Finished part categories include relay bases, motor brush cards, terminal blocks and automotive connector housings.
Polyethylene terephthalate compounds intended for thin-wall electrical supports are loaded with 10–14 wt% DFM0321-A and 3.5–5 wt% antimony trioxide to obtain UL 94 V-0 at 0.75 mm. The decisive limitation is the melt-temperature window: PET must be processed above its crystalline melting point, while the brominated epoxy resin darkens above 280°C. A desiccant dryer is operated at 140–150°C for 4–6 h to reach residual moisture below 50 ppm; wet regrind introduced at any ratio causes hydrolytic chain scission and measurable loss of elongation under ISO 527-2:2012. Injection moulding is performed at 265–275°C with hot runner manifolds not exceeding 270°C; backpressure is limited to 0.3–0.5 MPa to prevent shear-heat overshoot. Glow-wire end-product verification under IEC 60695-2-13:2021 commonly targets 775°C GWIT for unattended appliance components. Terminal parts produced in this scenario include lamp sockets, relay bases, transformer bobbins and switch mounting frames. The system is incompatible with amine-based stabilisers and certain organic pigments that accelerate depolymerisation; colour concentrates should be screened for volatiles and melt pH before production batches are released.
In 30% glass-fibre-reinforced PA66, DFM0321-A is typically incorporated at 16–22 wt% with 5–8 wt% antimony trioxide; for PA6 at the same glass loading, the starting range is 14–18 wt% DFM0321-A with 4–6 wt% antimony trioxide. Compliance is assessed by UL 94 V-0 at 1.6 mm, IEC 60695-2-12:2021 GWFI at 960°C for connector insulation parts, ISO 527-2:2012 for tensile properties and ISO 178:2019 for flexural modulus. Processing uses a co-rotating twin-screw extruder with 40:1 L/D and a vacuum vent maintained at 0.08 MPa; barrel temperatures are set at 260–285°C for PA66 and 240–260°C for PA6. The epoxy functionality of DFM0321-A can react with primary amine end groups of the polyamide under extended residence time, producing torque drift, melt-pressure oscillation and black specks; amine-based heat stabilisers and amino-silane coupling agents should therefore be excluded unless qualified in a pilot compounding trial. Pre-drying at 80°C for 8–12 h to below 0.15% residual moisture is mandatory; higher moisture causes hydrolysis and mould deposit on core pins. Finished components include automotive underhood connectors, circuit breaker internal frames, terminal blocks and cable glands.
| Polymer matrix | DFM0321-A loading | Antimony trioxide loading | Target vertical burning class | Processing ceiling |
|---|---|---|---|---|
| PBT | 12–16 wt% | 4–6 wt% | UL 94 V-0 at 0.8 mm | 250°C |
| PET | 10–14 wt% | 3.5–5 wt% | UL 94 V-0 at 0.75 mm | 280°C |
| PA66 30% GF | 16–22 wt% | 5–8 wt% | UL 94 V-0 at 1.6 mm | 290°C |
| ABS | 14–18 wt% | 4–6 wt% | UL 94 V-0 at 1.5 mm | 240°C |
| HIPS | 12–16 wt% | 4–5 wt% | UL 94 V-0 at 1.5 mm | 240°C |
ABS and HIPS enclosure compounds achieve UL 94 V-0 at 1.5 mm using DFM0321-A at 14–18 wt% with 4–6 wt% antimony trioxide in ABS, and 12–16 wt% with 4–5 wt% antimony trioxide in HIPS. Compounding is run on a co-rotating twin-screw extruder at 190–210°C for HIPS and 200–220°C for ABS; injection moulding melt temperatures are held at 210–230°C because styrenic polymers release monomer and discolour above 240°C. Pre-drying at 80°C for 2–4 h to below 0.05% moisture prevents surface silver streaking. Finished parts include television back covers, monitor enclosures, appliance control boxes and office automation housings; IEC 62368-1:2023 and RoHS Directive 2011/65/EU apply at final assembly level.
Where DFM0321-A is selected as the reactive brominated epoxy resin in FR-4 copper-clad laminates, it is introduced at 15–30 wt% of total resin solids, eliminating the separate addition of low-molecular-weight brominated powder in many varnish systems. The curing package typically contains dicyandiamide at 3–5 phr and 2-methylimidazole at 0.05–0.2 phr; antimony trioxide is not required because the brominated epoxy resin is chemically bound into the crosslinked matrix. Varnish mixing is performed at 60–80°C, followed by B-staging on vertical treaters at 130–170°C for 3–8 min. Lamination is carried out at 170–190°C and 2.0–3.5 MPa for 60–120 min. The cured laminate is evaluated against IPC-4101D and UL 94 V-0; glass transition temperature and flammability are measured by the corresponding IPC-TM-650 methods referenced in the customer slash sheet. Finished products are FR-4 multilayer printed circuit boards, copper-clad laminate panels and insulation plates. Process deviations that increase free amine content accelerate B-stage advancement and reduce prepreg shelf life; varnish solids and gel time should be re-qualified when solvent blend changes exceed 10%.
To produce flame-retardant polyester monofilament for woven cable harness sleeving, DFM0321-A is compounded into PBT or PET at 8–12 wt% with 3–4 wt% antimony trioxide, a lower loading than injection moulding grades because monofilament drawing increases surface-to-volume ratio and reduces the required bulk flame inhibition. The monofilament line runs a 0.2–0.8 mm spinneret die at 260–275°C; the extrudate is quenched in a water bath at 40–60°C, drawn at a ratio of 3.5:1 to 4.5:1 at 150–170°C, and annealed at 180°C for 10–20 min to stabilize shrinkage. Compliance is verified by UL 94 V-0 on the finished sleeve or tape, IEC 60695-2-12:2021 for electrical insulating sleeving, and RoHS Directive 2011/65/EU. Terminal products include automotive harness braided sleeving, cable protection conduits and flame-retardant industrial textile yarns. The filament process is sensitive to agglomerated antimony trioxide; packaging should remain sealed and regrind content should be held below 10% to prevent filament breaks and diameter variation. Published long-term heat-ageing data for this textile configuration is limited; validation should follow ISO 188:2021 at the target service temperature.
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Sichuan EM Technology Co., Ltd. model DFM0321-A is described in distributor documentation as a D-profile conductive fabric-over-foam electromagnetic interference shielding gasket with a single-sided conductive acrylic pressure-sensitive adhesive. The model code is parsed at the purchasing level as follows: DFM identifies the D-profile gasket series; 0321 identifies the cross-section family; -A identifies the standard adhesive configuration. The product is intended for board-level shielding can perimeters, display module frames, handheld RF compartments, and small-cell enclosure seams. The polyurethane foam core acts as a compression spring; the outer conductive fabric supplies the electrical path. The adhesive backing provides a tacky mounting interface to stamped metal flanges, die-cast housings, or PCB ground fences. Because the foam core is not a filled conductive elastomer, there is no environmental sealing function. Published primary datasheets for this exact model are limited in public repositories; the following discussion therefore distinguishes between class-typical engineering data for D-profile conductive fabric-over-foam gaskets and manufacturer-specific lot data that must be requested from Sichuan EM Technology Co., Ltd.
At the construction level, the gasket consists of three functional layers: a conductive textile outer sock, a polyurethane foam core, and a conductive acrylic pressure-sensitive adhesive on the flat mounting face. The conductive textile is typically a plain-weave polyester fabric plated with nickel, then copper, then a final nickel barrier. The copper layer supplies the bulk of the conductive path; the nickel layers provide corrosion resistance and mechanical hardness. The adhesive layer is filled with nickel or silver-coated copper particles to provide through-plane conductivity, allowing the PSA to act as part of the shielding circuit. The foam core does not require volumetric conductivity because the fabric external surface carries the surface current. The result is a lightweight continuous perimeter shield with a bend radius that is compatible with die-cut corner features.
The fabric is slit and formed into a D-profile sock around the polyurethane foam core. A seam is located on the flat base of the D-profile. The conductive PSA is then laminated over the seam, which reduces the risk of seam opening on the apex. This design places the seam away from the primary contact line, improving compression uniformity. Incoming components should be checked for seam alignment; a seam shift of more than 0.3 mm can create a hard spot on the apex and change local closure force. The supply chain should require a first article measurement of cross-section width and height with an optical profilometer, not a contact caliper, because the foam compresses under gauge force and underreports dimensional tolerance.
In low-closure-force handheld devices, the limiting variable is not always the fabric conductivity but the normal stress available at the gasket-to-flange interface. Conductive fabric of the nickel-copper-nickel plated polyester type used on the DFM series typically exhibits surface resistance below 0.1 Ω/sq when measured according to ASTM D4496-21e1. If the gasket is compressed below 20% of its initial height, metal flange flatness deviations greater than 0.1 mm can create slot apertures that degrade shielding effectiveness at frequencies above 1 GHz. At 6 GHz, one-tenth of the free-space wavelength is 5.0 mm; slots greater than this fraction begin to act as efficient antennas. The D-profile cross-section concentrates closure force along a narrow apex line, which raises local contact pressure compared with a rectangular strip of the same foam hardness. However, the same apex concentration means that poor mating flatness or excessive screw spacing can leave portions of the gasket uncompressed. In handheld designs where snap-fit features impose less than 0.2 N/mm of gasket length, shielding effectiveness may drop by more than 20 dB in the 1–6 GHz range. Production lot testing to IEEE Std 1302-2019 is therefore necessary to characterize transfer impedance as a function of compression, not as a single static value.
Measured shielding effectiveness for this gasket class is commonly reported at 70–90 dB from 30 MHz to 1 GHz when the gasket is compressed to 50% of nominal height in a rigid fixture. Actual values for DFM0321-A require lot-specific certificates because fabric plating weight, foam indentation force deflection, adhesive thickness, and die-cut edge quality vary between production campaigns. The dominant instability on stamped aluminium flanges is adhesive delamination at the die-cut perimeter; if flange roughness exceeds Ra 0.8 µm, the conductive acrylic PSA alone may not maintain long-term compression. In such cases the mounting flange should be cleaned with isopropanol, dried, and if necessary treated with corona or atmospheric plasma before application. Operators should not stretch the gasket during placement because stretching reduces the foam cross-section and can open the conductive fabric overlap seam.
The upper-frequency limit for a seam gasket is often established by the spacing between mating fasteners and the aperture formed by a non-conductive gap along the seam. The shielding effectiveness of a continuous conductive fabric strip can be undermined by screw-to-screw span. For a seam length of 30 mm between fasteners, the half-wave resonance occurs near 5 GHz. The conductive fabric surface must therefore be in continuous contact with the mating flange along the entire span. A single 0.2 mm wide gap can reduce shielding effectiveness by roughly 10–20 dB depending on the geometry and source impedance. DFM0321-A is designed as a compressible filler for these spans, but it cannot correct gross mechanical distortion. The assembly drawing should specify a maximum flange gap after closure of 0.1 mm and a minimum screw spacing no greater than 25 mm for frequencies above 3 GHz; alternatively, the design should use higher compression force or add conductive spring contacts at intermediate points.
Beneath the fabric layer, the polyurethane core of DFM0321-A supplies recovery force along the gasket axis. The D-profile geometry reduces initial contact area while increasing local pressure relative to a flat rectangular foam strip of equivalent density. Class-typical indentation force deflection for D-profile conductive-foam gaskets is between 0.10 N/mm and 0.30 N/mm at 25% deflection; published primary indentation force deflection data for DFM0321-A specifically are limited, so closure-force calculations should use ASTM D3574-17 Test C data from the actual production lot. The single-sided acrylic PSA is protected by a silicone-coated polyethylene release liner. The liner must remain in place until final placement because airborne particulates on the PSA reduce peel adhesion and create dielectric discontinuities. At the die-cut perimeter, the foam core is exposed; this edge is not conductive and should not be used as a shielding surface. Supplier documentation for the DFM series indicates that the product is supplied in roll format or as kiss-cut parts on a liner, but the exact roll length and liner orientation for DFM0321-A should be confirmed at the time of order.
Polyurethane foam gasket cores show time-dependent stress relaxation and compression set. The acceptance boundary commonly applied to conductive fabric-over-foam gaskets is compression set not exceeding 30% after 22 h at 70°C according to ASTM D3574-17 Test D. Below this threshold, the gasket recovers sufficient height after repeated thermal cycles to retain contact. Above this threshold, the D-profile loses rebound reserve and the residual height may fall below the minimum shielding plane, producing intermittent contact at the seam. In damp heat testing according to IEC 60068-2-78, exposed nickel-copper-nickel fabric edges can begin to corrode if the cut edges are not sealed or folded away from the seam. The purchase specification should therefore include a post-exposure contact resistance requirement, not only a visual corrosion criterion. Thermal expansion mismatch between the PSA, the fabric, and the aluminium or magnesium enclosure flange should be reviewed for continuous service above 60°C; continuous service above 85°C is not recommended for this product class because foam permanent set and adhesive softening can accelerate. Batch-to-batch variation in foam density may shift closure force by 15% or more; process capability data from the supplier should be requested for high-volume production.
When the gasket is used in an enclosure that sees rapid temperature cycling, the polyurethane core can take a compression set at high-temperature dwells. The indentation force deflection after 500 hours at 85°C is commonly reduced by 10–20% for this material class; the exact value depends on foam density and the initial compression. For designs where the gasket is compressed to 50%, a loss of 20% recovery force can drop the residual contact pressure below the threshold required for stable shielding. Thermal cycling tests should extend beyond 100 cycles from −40°C to 85°C with a dwell time sufficient to stabilize the enclosure, and contact resistance should be measured before and after cycling. Published data for DFM0321-A under this thermal cycling protocol are limited; the manufacturer should be requested to provide lot-specific thermal aging data.
In a small-cell 5G radio module, the shielding seam around the power amplifier and transceiver chain is often a die-cut conductive blanket or a metalized fabric-over-foam sheet. DFM0321-A is used when the mechanical stack requires a compressible perimeter contact that does not impose high thermal expansion stress or rigid metal-to-metal alignment. The adhesive side is applied to the PCB shield fence or the die-cast housing wall; the D-profile apex is then compressed by the lid or thermal spreader. Placement tolerance should be held to ±0.3 mm for manual placement and ±0.1 mm for pick-and-place die-cut parts on a polyester liner. A production-scale failure mode observed with this gasket class is liner stripping that tears the PSA from the foam core because the liner release force exceeds adhesive-to-foam anchorage. Liner release should therefore be tested at 180° peel angle and 300 mm/min using ASTM D3330/D3330M-04(2018) Test A against the actual liner material, not only against stainless steel. The gasket should not be stretched into position; stretch of more than 2% of free length can reduce the D-profile height and lower contact pressure below the threshold needed for stable shielding.
At the board level, the gasket replaces discrete grounding spring clips in specific designs where the available lid closure force is low. Unlike discrete spring contacts, the continuous D-profile strip provides a seam shield without periodic gaps between contact points. The continuous conductive fabric outer surface also avoids the periodic resonance windows that can occur with evenly spaced spring contacts at frequencies above 3 GHz. However, the foam core does not provide the same point-contact penetration as a beryllium copper finger; on oxidized aluminium surfaces, contact resistance may start higher and require greater compression. If the housing or PCB fence is not flat, die-cut gaskets may require a custom kiss-cut shape with inner radii no smaller than 1.5 mm to prevent fabric wrinkling and PSA buckling at corners. Incoming parts should be inspected for exposed foam through the fabric overlap seam; a seam overlap larger than 0.5 mm on the D-profile apex can create a hard spot that increases local compression force and may damage thin plastic latch features.
The matrix below summarizes engineering parameters that should be included in a lot-specific certificate of analysis for DFM0321-A. Values listed as class-typical are not a substitute for supplier lot data; specifications should be negotiated with Sichuan EM Technology Co., Ltd. before mass production.
| Property | Method or standard | Class-typical value or criterion | Notes |
|---|---|---|---|
| Surface resistance of conductive fabric | ASTM D4496-21e1 | ≤0.1 Ω/sq | Test on fabric before PSA lamination |
| Transfer impedance at 50% compression | IEEE Std 1302-2019 | ≤0.05 Ω | Use plated compression fixture |
| Shielding effectiveness 30 MHz–1 GHz | IEEE Std 1302-2019 | ≥70 dB | Compression 50%, flange gap 0 mm |
| Compression set 22 h at 70°C | ASTM D3574-17 Test D | ≤30% | Foam core only after fabric removal |
| PSA peel adhesion to stainless steel | ASTM D3330/D3330M-04(2018) Test A | ≥8 N/25 mm | 180° peel, dwell 20 min |
| Flame classification | UL 94 | V-0 or HF-1 | Supplier documentation must state fabric/foam/PSA assembly |
| Continuous operating temperature | Supplier thermal aging data | −40°C to +85°C | Published primary data for DFM0321-A limited |
Comparatively, DFM0321-A differs from conductive elastomer extrusions because it does not provide environmental sealing and is not formulated for repeated lateral shear. It differs from beryllium copper fingerstock because it is a low-cycle static seam shield rather than a sliding contact; the fabric can abrade at the contact edge under repeated mate/demate cycles and increase localized surface resistance. Compared with form-in-place conductive fluid gaskets, DFM0321-A allows die-cut rework and manual removal but adds a discrete part to the bill of materials and requires a bond line with finite width. The product is also distinct from conductive single-sided tapes and copper foil tapes: the shielding path in DFM0321-A is the outer conductive fabric sock, while the foam core acts as a compressible spacer rather than a conductive bulk medium. This distinction matters for designers attempting to use thickness alone as a proxy for shielding performance; the shielding function is present only at the fabric surface and the mounting plane, not through the entire cross-section.
Within the conductive fabric-over-foam category, DFM0321-A differs from rectangular-profile gaskets in the contact area at a given compression. The D-profile apex creates a narrower initial contact band, which reduces closure force at the beginning of deflection and allows the gasket to conform to mildly irregular flanges. A rectangular strip may provide a wider contact area and lower surface resistance after full compression, but it often requires higher closure force to achieve the same local contact pressure. DFM0321-A is therefore selected when latch loading is the limiting mechanical factor. Conversely, if the application can tolerate high closure force and requires environmental sealing, a silicone-filled conductive elastomer extrusion is more appropriate. The DFM0321-A profile should not be specified in a groove intended for an O-ring or conductive rubber because the non-conductive foam core will not resist fluid ingress and the outer textile can wick cleaning solvents along the fabric surface.
| Technology | Closure force | Shielding effectiveness | Environmental sealing | Rework | Typical mating cycles |
|---|---|---|---|---|---|
| DFM0321-A conductive fabric-over-foam | Low, 0.10–0.30 N/mm at 25% deflection | 70–90 dB up to 1 GHz, application-dependent | None | High, removable PSA | Static/low |
| Conductive elastomer extrusion | Medium to high, 0.50–2.00 N/mm | 60–100 dB depending filler | Possible | Low/medium | Static/dynamic |
| Beryllium copper fingerstock | Medium to high | 80–120 dB at high frequency | None | High | High |
| Form-in-place conductive fluid gasket | Low, very thin bead | 60–90 dB | Possible if dispensed as sealing bead | Low after cure | Static |
Storage conditions for conductive fabric-over-foam gaskets are generally specified as 12 months from date of manufacture in sealed polyethylene bags at 20–25°C and 45–55% RH. Exposure to ultraviolet light can degrade the polyurethane core and reduce PSA tack. The product should not be processed with amine-based primers or solvent vapor in the same cell because solvent uptake can swell the PSA and alter liner release. For first-article incoming inspection, the receiving site should verify splice-free inner core, continuous fabric seam, no exposed foam at the apex, and no liner delamination at the die-cut edges. The operational boundary for this gasket class is compression between 30% and 50% of nominal height; compression beyond 60% can crush the foam core and permanently reduce recovery force, while compression below 20% may fail to establish a stable low-impedance seam on rough flanges.
