WICOP LEDs

WICOP technology drops two components that define a conventional LED: the package and the bond wires used for contacting. Seoul Semiconductor calls the principle "No Wire, No Package". The chip is mounted flip-chip, contacts facing down, directly onto the circuit board, and the phosphor sits as a thin film right on top of the chip. Because the heat path does not run through a package and lead frame, thermal resistance drops sharply; removing the bond wires also removes a typical point of failure. This yields very low profiles, starting at roughly 0.4 mm.

The difference lies mainly in the package that has been left out. A conventional SMD LED (for example a 2835 or 3030) sits in a plastic body with a reflector cavity and is contacted by bond wires; the WICOP LED omits both, shrinking footprint, thermal resistance and stray losses. Against an ordinary chip scale package (CSP), Seoul positions WICOP as its own wafer-based generation, where contacting and phosphor are formed at wafer level and the light-emitting surface stays close to the chip size. For designers this means higher luminous density and better thermal coupling, but also more demanding assembly than with robust packaged types.

Neumüller stocks four WICOP series that differ mainly in package size and luminous flux:

• WICOP-Y11 (1.14 × 1.14 mm) – smallest package, for single spots and the highest luminous density
• WICOP-Y19 (1.81 × 1.81 mm) and WICOP-Y22 (2.21 × 2.21 mm) – mid-size high-output point sources
• WICOP 5050 (SZ9, 5.0 × 5.0 mm, 6 V / 12 V) – highest luminous flux, over 1,000 lm

Rule of thumb: choose the smallest package for tight optics and high luminous density, a larger package when flux and heat dissipation come first. The exact bin choice of flux, colour temperature and CRI is given in each series datasheet.

Besides luminous flux, colour temperature and CRI, the thermal parameters are the decisive ones for WICOP LEDs:

• Thermal resistance Rth(J–S) – roughly 0.45 K/W on the 5050 up to about 10 K/W on the small Y11
• Maximum junction temperature Tj – 125 to 150 °C depending on series
• Permissible forward current, and the power density that follows from it

Add to these the viewing angle (130–150°), the MacAdam colour binning (3, 5 or 7 step) and the ESD rating (Class 2 per JEDEC, the 5050 with an integrated protection diode). Check every limit in the datasheet before design-in.

The low thermal resistance is WICOP's core advantage, but it comes with a trade-off. Because chip and circuit board are coupled without a package, heat flows straight into the copper; on the large 5050, Rth(J–S) reaches about 0.45 K/W. The flip side: the tiny footprint of the small Y types concentrates power onto a few square millimetres and keeps their resistance higher (Y11 about 10 K/W), so they reach the Tj limit quickly without an adequately sized copper area or a metal-core board. High currents are only permissible with robust thermal management.

The wide viewing angle follows directly from the package-free construction: with no reflector cavity, the chip surface emits almost Lambertian. For wide, area-filling applications this is ideal, because light exits evenly and without package shadowing. Anyone needing a narrow spot or a directed beam profile must add secondary optics – a lens or reflector – since the LED itself does not collimate. The upside for beam forming is the small, bright source: a chip-sized surface lets compact optics shape a clean beam. Secondary optics, however, add build height and cost.

For automotive applications, the WICOP LEDs stocked by Neumüller are not intended: the range is aimed at general lighting, industry and lighting design. Seoul Semiconductor does use WICOP technology in automotive-qualified components, but AEC-Q102 qualified automotive LEDs are not part of the Neumüller portfolio. For vehicle applications with their qualification and documentation requirements, this product line is therefore not the right route. The Y11, Y19, Y22 and 5050 series are general-lighting types; their ratings and reliability evidence (LM-80, RoHS) relate to lighting applications.

WICOP LEDs pay off wherever high luminous density from a small area and good heat dissipation are needed. Typical applications:

• spots and directional luminaires with a defined beam
• industrial and high-bay lighting, downlights
• flood and street lighting
• compact high-output luminaires and torches

They are less worthwhile in simple, large-area low-cost applications with low power density – there, robust packaged standard LEDs are cheaper and more forgiving to assemble. Without a solid thermal and board design, WICOP cannot play to its strengths either.

WICOP LEDs are reflow soldered and handled like sensitive CSP components. Key points:

• Moisture sensitive (MSL 2), reflow at most twice
• Placement only with a vacuum nozzle, never tweezers – no pressure on the silicone surface
• Thermal design: enough copper area or a metal-core board
• Solder-pad layout, reflow profile (peak around 250–260 °C) and depaneling per datasheet

A visual and a functional check are advisable after soldering. Every limit and layout recommendation is in the respective series datasheet.