10 Minutes to Learn the Difference between IMD&COB Encapsulation

Ultimate Battle: IMD Vs COB  

For the last few years, we have heard opinions about COB prevail over traditional SMD with various technical advantages. Standing in the spotlight of LED industry, COB attracts constant attention and it becomes a consensus that COB is highly potential to spark a revolution.However, will all these go on as expected? After a general analysis of industry data, we found that up to this day, the most popular solution for P0.9 is neither SMD nor COB, but IMD. It is like a dark horse won the battle while the two strong competing. Below we will introduce you more details about the three techniques.

What are they? 

First, let’s figure out what are they. As three different encapsulating techniques, the simplest understanding is that they are different in the chip quantity.
To put it simple, SMD is individual component while COB is integrated packaging. And IMD can be considered as a small size integrated packaging with high speed SMT. It is a new generation product combines the advantages of both SMD and COB. No matter from the perspective of appearance or performance, it can meet the current market requirement.

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To put it simple, SMD is individual component while COB is integrated packaging. And IMD can be considered as a small size integrated packaging with high speed SMT. It is a new generation product combines the advantages of both SMD and COB. No matter from the perspective of appearance or performance, it can meet the current market requirement. 
MINI LED Display Solution under Technical perspective  
Monologue of LED Display:During my career, SMD as the leading technique solution, it used to be my best sidekick. Together we have witnessed the glory time of LED display industry. With the increase of market demand and development of application occasions, many fields like professional display, commercial display and household display needs me. However, I found it harder and harder for my old pal, SMD, to catch up with the paces of upgradation. (SMD encapsulation is limited to physical boundary, the finest solution now can only approach P1.2, a further demand on reducing pitch will lead to extreme high cost). Then I found IMD and COB, one is the innovator based on normal techniques, and the other one is a competitor with great talent who make its own new way. Which one should I choose?There are some crucial factors that decide if a product can become widely accepted: performance, cost and ability to put in mass production. Below we will analyse the difference between IMD and COB, then we will see who is more likely to become the mainstream technology in the future.
Round 1: Consistency
1.Consistency of CoatingIMD inherit SMD’s sorting technique which accumulated over a long period, and makes it have great color consistency after SMT in the application side. Although COB also improve in consistency, but it is not as stable as IMD. And it comes up sometimes that the consistency will go wrong in batches. From the perspective of whole industry, the point is that technical level of various COB factory differ with each other quite much, making it difficult to reach a standard.

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2.Color Consistency

LED display have a high demand on photochromic consistency, and the demand increased while the watching distance is lesser than 3 meters. Like traditional SMD, we can run fully inspection on IMD-M09T, after sorting and binning we can filter out the electrical defect. The consistency of photoelectricity can achieve the same level of 1010/0606. For COB, the usual way to mitigate color inconformity is die-bonding with fixed chips(this method also applied to IMD-M09T). After illumining engineers are able to repair the defect, but they can not assure the photoelectric parameter of all LED components are in a reasonable range. Also they need to use Point-by-point calibration technique, with limited effect. Therefore, to obtain a same level on color consistency, COB has pay much more cost than IMD. It is like in a battle, the decisive factor is not the muscle, but the weapon.

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 Result: IMD-M09T>COB 

More information: The cost of sorting in front-procedure and calibration cost in post-procedure is unavoidable for both IMD and COB, but due to the difference of encapsulating techniques, the cost needed is different.

Round 2: Control Cost
What we talk about here refer to the cost of display factory, as te producer of standard products, it is essential to control cost and create more value for downstream customer.First let us start with the cost of PCB board. Take P0.9 as example, normally for COB-P0.9 people use 8 layers, 3 levels. For IMD-M09T, since the LED itself has integrated circuits, it only needs 8 pins for 4 pixels, enlarge 50% space for wire-bonding on PCB. And factory which use IMD-M09T only need to make 6 layers, 2 levels, with a price drop of more than 20%. And for SMD, it also need PCB of 8 layers, 3 levels, with a leower request on accuracy.If you find it hard to understand, let us put it more specifically. “Layer”is like a chiffon cake, and “layer”is the craft.
difference between imd&cob6 onedisplay

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Besides, for now there are around one thousand PCB factories over the country, but only 2-3 of them can make 8 layers and 3 levels with high accuracy. From this fact we can tell how hard it is to control cost and technical practice. The reason why SMD can achieve mass production(also using 8 layers/3 levels) is that , the request on accuracy is not that high, so it lower the threshold a lot and many factories can make it.)  Normally the factories who can make HDI board have the ability to make 6 layers PCB board for IMD. Therefore, from the perspective of technical request or cost, 6 layers/2 levels board that IMD needed is lower than 8 layers/3 levels board that COB needed.

But there are a lot more cost than this for display factory. After production cost, let us go on with maintenance cost.

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More Information: The maintenance cost is mainly related to frequency of maintaining, and cost of labor. If it has to fix the whole screen, then it has to take the cost of raw materials into consideration. This Round: IMD-M09T>COB  
Round 3   Reliability and Protective Performance
It has to take various transportation for a LED display to reach customer side after finished SMT procedure. Therefore, protective performance is one vital factors to consider for display factory, especially for rental market. Since COB is integrated encapsulation, it is well sealed. Compared with SMD, the reliability of IMD has a great improve and satisfy customer’s request in current stage.More information: Factors that affect LED display’s protective performance:1. Adhesive force of epoxy and board2. Welding force of pin.
 This Round: COB >IMD-M09T  
After comparison and analysis
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From the perspective of concept and function, although COB has a certain space to improve, we have to admit that it is a good solution. However, we believe that only the most suitable technical path for end-customer can create great value for the whole industry, also win the market share and become the mainstream choice.