Before the word "CSP" appeared, the LED industry proposed the concept of "three nos", that is, "no package, no gold wire, no bracket", its packaging process is simple, the so-called no package does not really save the packaging link, but Part of the packaging process is advanced to the chip process stage, that is, the flip chip is directly sealed to the pad on the bottom of the package, without gold wire, without bracket, simplifying the production process, reducing the production cost, and the package size can be made smaller, and The same package size provides more power, which is CSP - chip scale package.
Since entering 2015, the LED industry has become increasingly popular with CSPs for lighting fixtures, and is considered to be the “subversive product†of the life of the LED packaging factory!
Based on the LED application wind direction began to favor CSP, many companies began to lay out CSP, for fear of being abandoned by CSP.
However, is it true that all packaging companies have capital, capability (technical capabilities and equipment capabilities) for CSP layout? For traditional packaging companies, because they have been working hard to dress LEDs, they have unique advantages in the production and process areas. There are also huge application groups in the application market. When the CSP concept came, enterprises, large enterprises, and listed companies that have been engaged in the packaging industry have stepped into the opportunities and did not want to miss the opportunity period.
But for small and medium-sized packaging companies, it is not that they can easily switch to the switch, because the company is small in size and scale, the application group is narrow, and the revenue is limited. If it is invested in CSP research and development, rectification equipment, equipment, technology There are great risks and uncertainties in the development of funds and product expansion. It is even more difficult to make a decision. At present, the development of CSP is still in its infancy, and its advantages are not obvious. Compared with the current package form, the CSP package still has several difficulties:
1. Comparison of light effect design and dressing chip does not have cost performance advantage;
2. Under the same power and light efficiency, the yield and technical maturity of the positive-loading chip are more advantageous than the current CSP;
3. When the same light output is the same as the luminous flux output, the formal wear also has an advantage;
4, the lighting manufacturers use the SSP of CSP and so on.
In view of this, what are the unknown and unresolved technologies for the CSP elite alliance in the LED lighting industry? After maturity, CSP has played an important role in the traditional flashlight and backlight display. Is it ideal in the field of lighting as expected? Chen Yong, general manager of Shenzhen Xinliangdian Electronics, was the host of this issue. As a supporting media, China Semiconductor Lighting Network hopes to further promote the future development of industry and enterprises through further exchanges and interactive discussions on CSP technology within the group. The following are the views of the participants in the discussion (for reference only):
[elite point of view]
Question 1: What is the current state of CSP LEDs?
Answer by: Chen Yong (General Manager of Shenzhen Xinliangdian Electronics)
The full name of CSP is Chip Scale Package, which means chip-level package and chip size package.
The current status of CSP LED: 1. The light efficiency is not high; 2. The reliability is to be verified; 3. The price is too high; 4. The ESD level is low; 5. The application-side placement accuracy requires high placement cost.
In response to the general manager of Rifu Yuan Haihui's suggestion that CSP has those advantages, Chen Yong answered: "The three mainstream structures of CSP unpackaged chips: 1. Made of silica gel phosphor, five-sided light, high light efficiency, but top and The surrounding color temperature consistency control is poor; 2. The top one light-emitting surface (single-sided light), surrounded by titanium dioxide to protect the fluorescent film, the light consistency and directivity is good, but the loss of ambient light output, light effect Severely low; 3. Fully covered with fluorescent film, and then fixed with transparent silica gel, the light quality is slightly poor (the color consistency is not good).
In answering the question of Wanjia Optoelectronics Zhang Dongyuan, it is also mentioned that because of the back plating, the reflection cavity or the quantum well on the bottom surface involves patent problems. However, from the application side, the current 2835 9v 100mA 1w product is between 0.11-0.16RMB, and the CSP LED needs a long time to precipitate, in order to achieve this cost performance. CSP's current application in backlights and flashlights is rapidly increasing, and it is expected to replace existing light sources in applications such as UV, lighting, landscape lights, and indicator lights. As a product under 30w indoors, it is possible to replace some of the SMD and cob markets.
CSP is used on the flash, mainly using CSP ultra-thin, small size, and lighting time only in an instant.
Question 2: In which areas does the CSP technology impact after it matures?
Answer by: Chen Yong (General Manager of Shenzhen Xinliangdian Electronics)
It does not affect the entire packaging industry, but is currently the mainstream form in the packaging industry. It belongs to the technical update of the chip link and not to the packaging world. It is just a product form, which is a supplement to the entire LED product category. It will not have much impact on the overall packaging situation in the short term. Of course, existing packaging plants still have their value and before the yield and cost of CSP products have not been resolved. In the field of lighting, SMD packaging, this cost-effective technology will still be the mainstream, can be expected to be SMD in at least 3-5 years, CSP yield problems have to be done for about 3 years, from the current good CSP factory The rate is roughly estimated at around 70%. Therefore, packaging companies should not scare themselves to death.
In 2016, packaging companies strive to improve the efficiency of machines, eliminate equipment with low capacity, and improve the yield through technological improvement. After the CSP mass production application, the price should not be a problem, mainly the CSP's current yield problem. In theory, it should be able to achieve a lower price than SMD.
Question 3: What problems does CSP have in large-scale lighting applications?
Answer by: Chen Yong (General Manager of Shenzhen Xinliangdian Electronics)
In the experimental application of lighting, I boldly predicted that a group of bosses who dared to eat crabs were photographed on the beach. It is recommended that the trial can be signed with the manufacturer.
Question 4: What technical difficulties still exist in CSP?
Answer by: Chen Yong (General Manager of Shenzhen Xinliangdian Electronics)
The CSP technology is transferred from the IC package. There are three main ways to connect the IC integrated circuit chip pad to the package substrate pad: flip chip bonding, TAB bonding, and wire bonding. Therefore, the CSP is developed. The packaging technologies that products need to develop can be divided into three categories:
1 Development of package technology for flip chip bonding CSP products
(a) Bump formation (electroplated gold bumps or solder bumps) techniques. Bumps are formed on the redistributed chip pads. (This bird technology is basically in the hands of foreign countries, and it has to be paid for using this technology)
(b) Flip-chip bonding technology.
(c) Bonding the chip with bumps face down on the substrate.
(d) Encapsulation technology.
When encapsulating, due to the thin thickness of the encapsulation material, the existence of voids and cracks will more seriously affect the reliability of the circuit. Therefore, it is necessary to reduce or even avoid the occurrence of holes and cracks during encapsulation. In addition, it is necessary to improve the water vapor permeability of the material. Therefore, in the encapsulation of CSP products, not only the encapsulation technology but also the encapsulation material with better performance is used.
(e) Solder ball mounting technology. Install solder balls under the substrate.
Step 1: Flip the bonding difficulties Ultrasonic hot-weld metal bump welding balls to ensure the ultrasonic welding temperature reaches 160 ° C stable combination (providing good passage for conduction and heat conduction, pay attention to thermal power is not separated) Spray uniformity, spray silicone material CTE and heat resistance
Step 2: Spray the phosphor before sorting the chip before spraying. The brightness is 1.1 times the wavelength of 2.5nm or less.
Step 3: Molding the lens precision mold and stable demoulding process.
Step 4: Cut. Blade cutting and laser cutting, the basic use of laser cutting is to avoid damage to the phosphor layer.
Step 5: Test the packaging, based on the above problems or technical difficulties, is there any specific improvement direction, for example, new materials, new packaging processes, or from the source of the chip to improve the crystal growth process.
Take 5w bulb as an example, CSP Â LEDs to replace the board made with 2835 5730 cob, the first consideration is the cost, the large chip CSP is actually using array technology. Once the application technology of CSP is mature, the cob factory is not good at first. Especially the small wattage bulbs are captured by 2835 1w and linear drive. The cob below 20w will gradually withdraw from the historical stage. However, in the future CSP products matured after the application of technology, the problem of size standardization will be a long-standing problem in the future.
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