Currently on the market a wide range of
COB, have their own characteristics. How to distinguish between various COBs, the following discusses the COB classification based on chip structure and the matching of various types of chips to COB substrates.
First, the chip
Differentiating from the chip structure can be divided into three categories:
1. The positive-loading chip COB: It is the most common product on the market at present. The high-reflective metal is used as the substrate at the bottom, and the laminated metal plate produced by the pressing process is used for product development. The reflection at the bottom can increase the side light of the chip. Collecting, while achieving the characteristics of thermoelectric separation and low thermal resistance.
problem:
a, the positive electrode chip area is shading.
b. The substrate material is sapphire and there is a thermal bottleneck.
c, the welding process is easy to cause death, etc., flicker.
d. The patented mirror aluminum substrate is in the hands of individuals, and the manufacturer has patent hidden dangers.
e. The substrate pressing process is not good, and water vapor intrusion and surface metal layer welding are difficult.
2, flip chip COB: currently the most promising COB products. Both large and small companies are promoting, and in the future we will be flipping COB.
The process saves the welding process and uses the patch process. Both capacity and reliability have been greatly improved.
The die bonding material can use metal solder to improve thermal conductivity and reduce thermal resistance.
problem:
a. Flip-chips are small in mass production, and the production capacity is small, so the price is expensive. In China, only a few companies such as Dehao Runda have achieved mass production.
b. The matching substrate line has high precision requirements, which is difficult for ordinary PCB companies to meet.
3, vertical chip COB: Rarely use vertical chip to make COB, but some people do it. The advantages of the vertical chip are high brightness, large heat transfer area, and low thermal resistance.
problem:
a, if the use of silver glue solid crystal is easy to open the way.
b. With metal solder, a single pad can cause soldering offset.
c. There are few vertical chip manufacturers and few takeaways.
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