The light-emitting diode matrix is understood to be a periodic structure of any kind consisting of identical elements (light-emitting diodes or LED) which are mounted on a current-carrying surface (flat or volumetric).
Later on we will consider the designs of the matrixes and carry out their technical and economic comparison.
Flat matrixes consist of a flat current-carrying surface with light-emitting diodes mounted on.+ There are some versions of FLED М.
1.1 FLED matrixes on discrete elements.
This type of matrix is made on the printed-circuit-board with some individual light-emitting diodes (LED) being mounted on.
The matrix is simple to manufacture and doesn't require any special equipment. Installation of LEDs can be done manually with a soldering tool. LEDs can be mounted both in one row and in several rows.
When LEDs are mounted in one row, the matrix can be called linear. This type of matrixes is widely applied in lighting alarm devices of cars and automobiles, for example for additional braking signals.
LEDs are cooled by heat removal from a LED crystal through LED leads to board conductors. The current going through the crystals can't exceed the recommended values specified for the given type of LED.
1.2 FLED М on РСВ-TECHNOLOGY
This type of matrix is a printed-circuit-board with LED crystals being mounted on the conductors. The crystals are glued to the conductors with a special glue which can be either current-carrying or not current-carrying. The glue required depends on the type of a crystal.
The fragment of the FLED М on РСВ-technology is shown in the picture.
1.3 FLED М on the light-emitting diodes of SnapLED type.
The company Lumileds has developed light-emitting diodes SnapLED on the basis of the InGaAlP-chip. This light-emitting diode has massive flat leads which provide effective heat removal from the light-emitting crystal (chip). The design of the light-emitting diode is shown in the picture.
The installation of the SnapLED light-emitting diodes is done on metal plates by means of rivets
FLED М on light-emitting diodes SnapLED is shown in the picture.
An electronic control module is mounted on the printed-circuit-board which is fixed under the FLED М.
Good heat removal allows to conduct the current through the light-emitting crystal SnapLED of the diode which is 2..3 times more powerful than that of the light-emitting diode made on the standard technology. Thus, a usual crystal (chip) can provide a 2…3 times more powerful light stream.
The metal plates of the matrix are fixed on the rigid dielectric basis to eliminate vibration during the operation.
While designing light-emitting diode devices for car and automobiles it is necessary to outline the contours of the body. The body of a modern automobile has an irregular shape, and it is sometimes very difficult "to include" flat light-emitting surfaces into it. This task can be solved with the help of volumetric 3D-matrixes.
3D-matrixes on light-emitting diodes SnapLED
To produce a volumetric matrix on light-emitting diodes SnapLED is possible with the help of shaping or curving of metal plates where light-emitting diodes are mounted.
After LED have mounted on the matrix, the latter is fixed onto the dielectric (plastic) basis which outlines the form of the matrix.
This technology allows to lessen dimensions of the lighting device. The lights of a car on 3D-SnapLED matrixes are shown in picture (а) and on bulbs – on picture (в).
Good heat removal from the light-emitting crystal and possibility to outline the shape of a surface where it is fixed allow to provide the required lighting characteristics as well as to lessen the size of the device.
3D-matrixes produced with the technology of the company 'LightTech plus' (3D-LT-matrixes)
The company 'LightTech plus' has developed the technique to manufacture volumetric matrixes with the use of transforming printed-circuit-boards. A unilateral scribing (internal grooving) is done on printed-circuit-boards which allows to transform the printed-circuit-board to fit the necessary form. After transformation the LED and other necessary electronic components are mounted on the printed-circuit-board. The bilateral printed-circuit-board provides effective heat removal from LED leads. Both sides of the printed-circuit-board participate in the cooling process/ The sides are coated with copper foil and connected by means of large number of metallized holes. The current going through the LED can be increased twice in comparison with the nominal value.
Surface curvature of the matrix depends on the scribing spacing in vertical and horizontal directions. Smooth change of spacing allows to receive a smooth change of the shaping or curving radius. The less the scribing spacing is, the more precisely is the copied surface. The size of spacing is limited to the size of the contact platform necessary for mounting the LED.
A 3D-LT-matrix with scribing spacing change in a horizontal direction is shown in the picture.
The matrix is fixed on the body of the product with self-tapping screws.
3D-LT-matrixes make it possible to provide the required lighting characteristics in such units where technologies applying usual bulbs can't ensure the desirable result as the space for a reflector and a lamp holder is not available. In this picture see the top parts of car lights which have a triangular form and a small thickness (depth).
The ready to use sections of the lights look as follows:
The light module of a triangular form.
The light module of a triangular form.
3D-LT-matrixes allow to outline the concave surfaces through bending the printed-circuit-board in the reverse side. One of the variants is shown in the picture.
If scribing spacing is smoothly changing both vertically and horizontally, the surface of the matrix takes a form of a sphere.
Thickness of 3D-LT-matrix makes up 1,5…2,5 cm.
Thus, 3D-LT-matrixes make it possible to design units with practically any surface. Matrixes have thickness up to 1,5 cm which provides new opportunities while designing car light devices.
Technical and Economic Comparison of 3D-matrixes
To compare matrixes we have to introduce the parameter of efficiency $/lm which equals to the ratio between expenses for manufacturing of the matrix in US dollars and a luminous power (flux) in lumens received from the matrix. The calculations are done for the surface of 1 sq. decimeter with 16 LEDs.
1. Flat light-emitting diode matrixes on discrete LED are advisable to apply in units which have no significant bends. The cost of 1 sq. decimeter of the unilateral printed-circuit-board is 1 $. The cost of 1 LED is 0,15 $. The luminous power (flux) of 1 LED is 2,3 lm.
2. Flat light-emitting diode matrixes on РСВ-technology.
3. Flat light-emitting diode matrixes on light-emitting diodes SnapLED.
4. 3D-matrixes on light-emitting diodes SnapLED.
Thus, basing on the parameter of efficiency we have come to a conclusion that 3D-LT-matrixes (the parameter of efficiency – 0,062) are the most efficient. The second position belongs to FLED M on light-emitting diodes SnapLED, then – FLED M on РСВ-technology (0,069), 3D-matrixes on light-emitting diodes SnapLED (0,073), and FLED M on discrete light-emitting diodes (0,092).
The application of the above mentioned LED technologies in light-signal devices with bulbs in industrially produced cars and automobiles, as a rule, does not ensure any improvements in design and lighting characteristics. Even after 'a special modification' though a lamp lens remains without any significant change, but the internal part of the body is considerably changed, the unit does not allow optimum installation of light-emitting diode matrixes.
For an effective use of LED technologies it is necessary to provide for their application simultaneously with the design of a new car. Besides, it is important to thoroughly consider a cost factor.
The following advantages of LED technologies over bulb technologies should be taken into account:
The complex approach reveals all the advantages of LEDs while manufacturing car light-signal devices and allows to make a purposeful and conscious choice for benefit of light-emitting diode technologies.