Book 12:   COB LED arrays and holders

March 2017: Book 12 Edition 1.1 is now published

Book 12 defines a family of rectangular and square LED arrays with a circular light-emitting surface (LES). These arrays require a separate LED driver, and can be used either with or without holders, depending on the luminaire type and application.

Book 12 Edition 1.1 also describes array holders.

The LED arrays in Book 12 have the following overall dimensions:

Category Size and shape Category Size and shape
C12x15 Rectangular 12 x 15 mm C20x24 Rectangular 20 x 24 mm
C16x19 Rectangular 16 x 19 mm C24x24 Square24 x 24 mm
C19x19 Square 19 x 19 mm C28x28 Square 28 x 28 mm

The holders in Book 12 have a cavity in the rear that accommodates a COB array. The size of the cavity corresponds to one of the array sizes shown in the Table above.

The outer dimensions of the holder correspond to the LED modules defined in Zhaga Book 10 i.e an outer diameter of either 35 mm (category D35) or 50 mm (category D50).

The combination of a COB module and a suitably-sized COB holder can create a product that effectively replicates a Zhaga-based spot LED module as described in Book 10.


For an overview of Book 12 and how it relates to Book 10, watch the video below or download the presentation

Publication status

Public downloads are available:

Download Book 12 (English) - Edition 1.1, March 2017

The Zhaga Consortium will review and update this specification from time to time. To ensure you are aware of any updates to the Zhaga specifications, please subscribe to the Zhaga newsletter.


Most Book 12 arrays will use chip-on-board (COB) technology for the light-emitting section. However, Zhaga does not prevent the use of alternative technology approaches.

The diameter of the circular light-emitting surface (LES) is limited by the overall size of the array and the need to accommodate the electrical contact pads. The LES categories in Book 12 correspond to those in the Zhaga Spot Book 10. The pemitted LES categories in Book 12 range from LES6.3 (LES diameter 4.5-6.3 mm) to LES30 (LES diameter 23.0-30.0 mm).

Book 12 specifies the interface between a COB LED array and a COB holders. The interface between a holder and an LED luminaire is defined in Book 10.

Book 12 COB products from Samsung and Lumileds at the Zhaga booth at Light+Building 2016. See our "News from Zhaga Members" page for more details. 

Lumileds COB arrays on display at Light+Building 2016. 

COB holder products from Molex at Light+Building 2016.

Video describing the use of BJB holders with Bridgelux COB arrays. See also the article on LED Professional's website.

COB holders from TE Connectivity on show at Light+Building 2016. The 35-mm-diameter holder (left) corresponds to Zhaga Book 11, while the 50-mm versions (right) correspond to Book 3.