Book 12: COB arrays

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

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

Book 12 defines a family of modules with the following PCB 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 diameter of the circular light-emitting surface (LES) is limited by the overall size of the module, and the need to accommodate the electrical contact pads. The LES categories in Book 12 correspond to those in the Zhaga Spot Books 3 and 11. 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). 

Publication status

Public downloads are available:

Download Book 12 (English) - Edition 1.0, March 2016

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.


Article (September 2015): Chip-on-Board LED modules standardized in Zhaga Book 12
This article, published in LED Professional, describes the numerous issues that have been addressed by Zhaga on the way to developing a mechanical interface specification for COB LED arrays.



COB arrays are commonly (but not exclusively) used with holders. 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 either Book 3, 10 or 11.

Edition 1.1 of Book 12 will specify the interface between COB LED arrays and COB holders. The definition of the COB–holder mechanical interface will include features such as the size of the cavity in the holder, the position of contacts, and the keep-out zone.

Photo Gallery

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.