The so-called COB is to bond bare chips with conductive or non-conductive adhesives on the interconnection substrates, and then wire bonding to achieve their electrical connection. If the bare chip is directly exposed to the air, it is vulnerable to pollution or man-made damage, affecting or destroying the function of the chip. So the chip and bonding wire are encapsulated with glue, which is also called soft package.
The bare chip packaged with LED COB is the main body of the chip and the I/O terminal on the top of the crystal. When welding, the bare chip is bonded to PCB with conductive/thermal adhesive. After solidification, the metal wire (Al or Au) is connected to the I/O terminal welding area of the chip and the corresponding pad of PCB by ultrasonic and hot pressing with Bonder machine. After testing, the resin glue is sealed again.
Compared with traditional packaging technology, LED COB packaging has the following advantages: low price; space saving; mature technology.
LED COB package
also has shortcomings: it needs to be equipped with welding machine and packaging machine. Sometimes the speed can not keep up with; the PCB patch has more stringent requirements towards environment; it can not be maintained. LED COB, this traditional packaging will play an important role in the packaging of portable products.
Common Problems of LED COB Package
Q: Color temperature displacement in cob packaging technology of led light source.
A: The high baking temperature shortens the distance between the electrodes, curtailing the time from gelling to baking. The difference in color temperature should be caused by the precipitation of phosphor. It is suggested that the fluorescent powder should be baked in time after gelling, and increase the temperature to make it harden quickly to avoid the precipitation of phosphor. Review the temperature rising curve of OVEN box.
Q: In the packaging technology of LED, what is the difference between Lamp LED packaging technology and COB packaging?
A: LED COB packages are generally suitable for the use on the same substrate as other electronic components.
If LED COB is made into direct insertion package, it should have some special functions such as flicker function, digital character, color control module and so on. Large and small power can be used as COB or lamp, there is no difference in this respect.
Q: Will LED COB integrated package
be used as planar light source instead of today's patch products?
A: There will be no substitution. Both of them are future developments and will coexist for a long time.