2835 LED Buyer Starter Pack (2025): Meaning, Watt Math, Dimming Rules, SMD Basics & 2835 vs 5050

Meta title: 2835 LED Explained (2025): Watts, Dimming, SMD & 2835 vs 5050Meta description: Straight answers for U.S. wholesale buyers: what “2835” means, real wattage, dimmability, SMD assembly best practices, and when 2835 beats 5050—with RFQ lines you can paste.

You’ve read a dozen “SMD 2835 high-efficiency” pages and still don’t know what 2835 is, how many watts it really draws, or if it will dim without flicker.That guesswork leads to hot strips, camera banding, tint mismatch—and returns that erase your margin.Use this starter pack: five practical sections with purchase-grade specs, RFQ sentences, and quick tests you can run before issuing a PO.

Know the footprint, do the watt math, demand flicker metrics, reflow SMDs right, and choose 2835 or 5050 by $/klm landed—not brochure promises.

If you buy lighting for New York distribution, your Google history probably cycles through “What does 2835 LED mean?”, “How many watts is a 2835?”, “Is 2835 dimmable?”, “What does SMD mean?”, and “Which is brighter, 2835 or 5050?” Those five questions decide whether your next rollout ships friction-free—or becomes late-night support calls and rushed airfreight.

Here’s the plain-English baseline from XGM (Shenzhen Xinguanming)—14 years of LED R&D serving 3,000+ customers across automotive, retail, appliances, outdoor, and beauty lighting:

“2835” = a package size: 2.8 × 3.5 mm mid-power SMD with an exposed thermal pad. The geometry favors tight pitch and efficient heat into copper.

Wattage isn’t printed on the part. Real power is I × Vf. Push current without upgrading thermals and a catalog “0.2 W” quietly becomes 0.36–0.5 W, which shrinks lifetime and shifts color.

Dimming can be perfect—if drivers meet IEEE 1789 (Percent Flicker/Flicker Index), PWM frequency is ≥2–4 kHz (or CCR), and the phosphor blend doesn’t smear color at low duty.

SMD means surface-mount device: reflowed parts that reduce labor and improve heat flow—if stencil, paste, and profile keep voids low under the slug.

Brightness reality: 5050 wins per-package punch and rules RGB. For dense white strips normalized to $/kilolumen landed (unit + freight + duty + bin premiums), 2835 often wins with calmer thermals and smoother diffusion.

Each section below follows PAS and adds RFQ lines you can paste into vendor emails. We also call out E-E-A-T signals procurement teams look for: LM-80/TM-21, EN 62471, RoHS/REACH, and binning rules (SDCM/ANSI). Use this as your standard spec; we can pre-bin, ship pilot lots, and provide native test PDFs on request.

1·“2835” in One Sentence: A Size Code, Not a Brightness Grade

“2835” is the 2.8 × 3.5 mm mid-power SMD footprint with an exposed thermal pad—tight pitch, stable thermals, high SMT yield.

Problem. Teams treat “2835” like a lumen class, then mix reels as if all 2835s are identical.Agitate. That’s how you get green/pink zebra shelves, hotspots, and reflow rework that blows deadlines.Solution. Treat 2835 as geometry. Inside the rectangular package sits a single InGaN blue die on a reflective leadframe, topped with phosphor, and bonded to an exposed slug that conducts heat into copper. This format thrives on 8–12 mm strip PCBs at ~120 LED/m, delivering smooth diffusion with manageable junction temperatures. In 2025 production, Ra80 whites often deliver strong efficacy at ~65 mA; Ra90 variants trade a little lm/W for R9 ≥ 50—great for retail and medical-beauty. For uniform visuals, enforce ≤3 SDCM (general·or ≤2 SDCM (retail/camera). Require LM-80/TM-21 lumen-maintenance reports, EN 62471 photobiological safety, and RoHS/REACH compliance—native PDFs from accredited labs, not screenshots.

Lock these into drawings and RFQs:

Thermal path: RθJC ≤ 12 °C/W; staggered micro-vias under the slug; 2-oz copper on FR-4 for 0.2–0.24 W; step to MCPCB above ~0.30–0.36 W.

Materials & environments: Silver-mirror leadframes lift lm/W but risk sulfur tarnish near leather/rubber—spec anti-sulfur encapsulant. See sulfur mitigation brief.

Color discipline: Limit shipments to ≤2 adjacent bins; label reels with CCT, Duv, Ra, R9, lm, Vf, lot. Template: bin map + certificate.

Polarity & pads: Lock cathode orientation; share the pad/stencil file early to prevent tombstoning: 2835 pad & stencil card.

RFQ copy: “2835 package 2.8×3.5 mm with exposed pad; RθJC ≤ 12 °C/W; ≤3 SDCM (≤2 optional); anti-sulfur encapsulant; native LM-80/TM-21, EN 62471, RoHS/REACH PDFs.”

2·How Many Watts Is a 2835 LED? (Do I × Vf—and check the heat path

Wattage isn’t a sticker; it’s current × forward voltage. Lifetime is set by Tj, not marketing.

Problem. A “0.2 W 2835” gets driven like 0.36–0.5 W without upgrading the substrate.Agitate. Junction temperature spikes, L70 shrinks, white drifts green/pink, and returns pile up.Solution. Compute Pd = I × Vf using your actual driver current and the supplier’s Vf histogram. Typical catalog point: ~65 mA × ~2.9 V ≈ 0.19 W. Turn the current up to ~120 mA × ~3.0 V ≈ 0.36 W—acceptable on MCPCB, risky on thin FR-4. Estimate ΔT = Pd × RθJC and add board-to-ambient (RθCA·to get Tj; keep Tj ≤ ~105 °C for honest LM-80/TM-21 outcomes. Need more flux? Under-drive and add emitters; eight 2835s at 65 mA often beat three 5050s on lm/W and hotspot control. Also cap driver ripple < 5 %—peaks, not averages, kill LEDs.

Controls you can enforce:

Vf window & distribution: Spec typ 2.8–2.9 V; max 3.1 V @ 65 mA and request the histogram (actual lot spread), not just min/max. Primer: Vf-histogram guide.

String strategy: Prefer series; if you must parallel, add balancing resistors or matched copper lengths to avoid current hogging.

Driver topology: Constant-current buck; prefer spread-spectrum PWM to limit EMI and current peaking.

Thermal step-up: Beyond ~0.30–0.36 W per LED, move to MCPCB and verify thermocouple temps at Tc. SOP: thermal check sheet.

RFQ copy: “Quote lm/W at 65 mA and at our max current; provide Vf histogram, RθJC data, ΔVf after 1,000 h @ 85 °C/IFnom, and derating curve.”

3·Is 2835 Dimmable? Yes—If You Respect Flicker Physics

Use 2–4 kHz PWM or CCR, verify IEEE 1789 metrics, and check low-duty Δu′v′.

Problem. Constant-voltage strips on triac wall dimmers produce ripple and camera banding.Agitate. Guests see strobe; staff complain of headaches; reviews mention “flicker.”Solution. Pair 2835 strips with PWM ≥ 2–4 kHz or CCR drivers for sensitive spaces. Put two numbers in writing: Percent Flicker < 10 % and Flicker Index < 0.05 at full output. Then test where cheap drivers fail—~20 % dim level. Ask for a phosphor decay curve; fast-decay mixes track PWM better (less smear), while slow-decay hides strobe but warms CCT. Require Δu′v′ ≤ 0.003 from 100 % → 10 % at Tc 25/55 °C so whites stay consistent on camera.

Dimming checklist to hand your engineer:

Driver choice: PWM (≥2 kHz; 4 kHz ideal·or CCR; add a shunt FET to stop ghosting <2 % duty.

EMI discipline: Spread-spectrum controllers reduce RF noise and peaking—important in hospitality/retail.

Metrics & proof: Capture Percent Flicker, Flicker Index; optionally Pst_LM/SVM. Request scope screenshots at 100 % and 20 % on your load.

Layout: Keep LED-to-driver traces short; solid grounds reduce ringing/overshoot that can cook LEDs.

Reference handouts: IEEE-1789 quick card · low-duty test SOP

RFQ copy: “Provide IEEE 1789 metrics and Δu′v′ vs dim level using our driver; attach oscilloscope screenshots at 100 % and 20 % output.”

4·What Does SMD Change? Assembly & Heat—Not Hype

SMD = surface-mount device: faster builds and better thermals—if stencil, paste, and profile keep under-slug voids low.

Problem. “One stencil fits all” invites voids and tombstoning on 2835 pads.Agitate. Voids push RθJA up; skew kills yield; schedules slip.Solution. For 2835, use 0.12–0.15 mm stencils, type-4/4.5 paste; ramp < 3 °C/s; peak 245 ± 5 °C (nitrogen preferred). X-ray first articles: if void area under the slug exceeds ~30 %, tune apertures or insert a soak segment. Prefer no-clean flux to avoid moisture under lenses; bake PCBs stored > 6 months. Share a one-page reflow card with the EMS before first build.

On-floor practices that pay off:

Area ratio ≥ 0.66 for reliable paste transfer; consider step stencils over the thermal pad.

Aperture reductions aligned with copper to limit float/skew; avoid lens shadowing.

Sampling & rejection: IPC-7093 X-ray sampling; reject lots with repeat void hotspots; tweak soak/peak timing.

Cleaning policy: Avoid water-soluble flux under lenses; if used, validate wash + bake cycles with Δu′v′ checks.

Downloadables: SMT setup checklist · void-control guide · stencil/pad drawing

RFQ copy: “Provide pad layout, stencil guidance, max void %, and recommended reflow curve for the quoted 2835; confirm IPC-7093 compliance.”

5·Which Is Brighter: 2835 or 5050? Compare by Use Case and $/klm Landed

Per package, 5050 is brighter; on dense white strips and $/kilolumen landed, 2835 usually wins. RGB still belongs to 5050.

Problem. Teams compare single-package lumens and ignore density, drivers, and heat.Agitate. You overbuy 5050s, drivers run hot, and diffuser hotspots appear; BOMs bloat.Solution. Normalize every quote to $/klm landed (unit + freight + duty + bin premiums). A white 5050 (often multi-die·hits strong lumens at ~150 mA, out-punching a 0.2 W 2835 at ~65 mA. But eight 2835s spread heat, maintain lm/W, and often beat three 5050s on $/klm once drivers and logistics land on the invoice. For RGB, 5050’s tri-die layout is mandatory. For outdoor “punch,” 5050 white works—just derate ~20 % and add surge protection.

How to compare fairly:

Color quality premiums: Ra80 vs Ra90, R9, and SDCM—price these explicitly.

Thermal headroom: Compare Tj at worst ambient; derate if fixtures trap heat.

Driver BOM: RGB/5050 may need more channels and higher PWM—cost and EMI risk go up.

Supply risk: 2835 whites are broadly second-sourced; addressable 5050s can lock you to one IC vendor.

Tools to wire later: $/klm calculator · use-case matrix · addressable RGB note

RFQ copy: “Quote 2835 white (Ra80/Ra90·and 5050 white/RGB as $/pc and $/klm landed (FOB & DDP NY). Include SDCM, RθJC, IEEE 1789 metrics, surge limits, and lead time.”

Binning: ≤3 SDCM (≤2 premium); shipment ≤2 adjacent bins; reel certificate lists CCT, Duv, Ra, R9, lm, Vf, lot.

Thermal & Reliability: RθJC ≤ 12 °C/W; HTOL 1,000 h @ 105–125 °C, 85/85 1,000 h, –40↔125 °C 1,000 cycles, surge 10/700 µs to 2 kV; lumen loss ≤ 10 %, ΔVf ≤ 0.1 V, Δu′v′ ≤ 0.006.

Dimming: Provide IEEE 1789 metrics; Percent Flicker < 10 %, Flicker Index < 0.05 at 100 %; verify at 20 %.

Compliance: EN 62471, LM-80/TM-21, RoHS/REACH—native PDFs.

Pricing: Quote $/pc and $/klm landed (FOB Shenzhen & DDP New York); itemize bin premiums; include NET-30/NET-60 options.