In-depth discussion of flip-chip structure package

Yesterday, we released the “Clippery Structure Packaging Process and Application Market Analysis”, and today we continue to deliver the exciting interactive part of the second part! A total of 13 interactive questions and professional answers from Terrence teachers have been selected.

1. Cost comparison of two packaging methods

What is the difference between the cost of the two packaging methods? - Mao Chengkui

At present, in terms of cost and comparison between two light effects, the cost of flip chip structure will be higher than that of formal dressing, depending on the technical production efficiency problem, and the material difference will not be too large.

2. How to break through the crystal effect of flip chip COB?

Based on the comparison with the mirror-mounted aluminum COB, how does the flip-chip COB break through? Light effect? Heat transfer? ——Deng Yucang

Overmolding COB should make a breakthrough in light efficiency:

First of all, we must solve the problem of ink. In fact, this ink needs to be modulated. It may not be possible to buy the ready-made products to meet the application requirements.

Second, in the chip, you may want to choose a higher-end chip;

Third, when eutectic soldering, care should be taken to minimize the loss of light.

3. How to solve the problem of thermoelectric separation?

What is the solution for thermoelectric separation? ——Xue Shuiyuan

To achieve better thermoelectric separation, you can choose a superconducting aluminum substrate with better insulation effect, or choose an aluminum nitride substrate. In this structure, its heat and electricity can be separated.

4, eutectic process void control standard

Is there a standard for eutectic process void control in high-density COB plants? ——Lu Yuchun

The problem of void ratio for eutectic soldering depends mainly on which eutectic soldering method you use, whether it is hot-pressed eutectic soldering or flux eutectic soldering. The general standard is personally considered to be less than 15%.

5, eutectic method on the surface treatment of the substrate metal layer

Is the eutectic method necessary to treat the surface of the metal layer of the substrate with gold or nickel-palladium? Is it possible to plate silver or sink silver? —— Mai Huafeng

Gold will be better and will help solder.

6, COB lamp beads light efficiency test

Now with COB's lamp beads, how much is the highest luminous efficiency in the industry? ——Jiang Zhongliang

The individual knows that it should reach 190 lm/W. There is no argumentation. It is uncertain whether it is laboratory data or actual application data. It is estimated that the actual application data cannot reach such a high level.

Personally think: LED single shot in the integrating sphere is tested for all the luminous flux emitted. In the distributed photometer test method, there is a baffle that blocks part of the light. Therefore, I feel that it is not accurate to test the efficacy of a single LED with a photometer. Personally, it is reasonable to measure the light distribution angle of the photometer, and the test light effect and so on are not very accurate. ——Jiang Zhongliang

In testing the light effect, we need to figure out one thing, the luminous efficiency of the LED and the light extraction efficiency of the integrating sphere are not consistent. In many cases, the light emitted by high-density products cannot be completely captured by the integrating sphere, which is the cause of the decline in metering efficiency.

7, what is good on the silicon substrate

What is the substrate silicon of Professor Jiang Jiang? What are the advantages and disadvantages? ——He Xueming

Silicon substrates have better thermal conductivity than sapphire.

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