COB Process Introduction and Precautions
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COB (Chip on Board) is a method of directly attaching a bare die to a circuit board, and directly bonding the wire to the gold-plated circuit of the PCB. Then, the IC packaging step is transferred to the circuit board through the sealing technology.
The evolution history of electronic chip packaging is from IC packaging ' COB ' Flip Chip (COG), and the size is getting smaller and smaller. In the past, COB technology was generally used in consumer electronics products that did not pay much attention to reliability, such as toys, calculators, small displays, clocks and other daily necessities, because most manufacturers that make COBs generally consider Low Cost. Nowadays, more and more manufacturers value its small size and the trend of thin, light and short products, and there is an increasing trend in its use, such as mobile phones and other short-required products.COB has another advantage that makes some PCBA processors particularly fond of it. Due to the need for sealing, ordinary COBs will seal all external lead pins in epoxy resin. For those hackers who like to crack other people's designs, it may take more time due to this feature. To crack, indirectly to improve the level of anti-hacking security.It is recommended to have a clean room and the class should be below 100K. Because the COB process belongs to the wafer packaging level, any small particles contaminating the solder joint will cause serious defects.Basic dust-free clothing is also necessary. It is not necessary to wrap the head into a meat-like dust-free clothing, but basic hats, clothes, and electrostatic shoes are all required.In addition, the clean room should strictly control the entry of cardboard boxes and any items that are easy to carry or generate debris. All packages should be unpacked before entering the clean room. This is to keep the clean room clean and extend the life of the clean room.3.1. The surface treatment of the finished PC board must be gold-plated, and it must be thicker than the gold-plated layer of ordinary PC boards, in order to provide the energy required for Die Bonding to form gold-aluminum or gold-gold co-gold.3.2. As far as the layout of the pads outside the COB's Die Pad is concerned, try to keep the length of each bonding wire fixed, that is, the distance from the die to the PCB pads should be the same. Therefore, the design of diagonal pads does not meet the requirements. It is recommended that the PCB pad pitch be shortened to eliminate the appearance of diagonal pads.3.3. It is recommended to have at least two positioning points for a COB wafer. We hope to use the cross-shaped positioning points instead of the traditional circular positioning points, because the Wire Bonding machine will grasp the straight line for positioning when it performs automatic positioning. . There may be some Wire Bonding machines that are not the same. It is recommended to refer to the performance of the machine to make a design first.3.4. The size of the PCB's (Die Pad) should be larger than the actual die to limit the offset when placing the wafer, but it should not be too large to avoid the wafer from rotating too much. It is recommended that the wafer pads on each side be 0.25 ~ 0.3mm larger than the actual wafer.3.5. It is best not to arrange vias in the area where the COB needs to be glued. If it cannot be avoided, these vias must be 100% completely plugged to prevent Epoxy glue from penetrating the other side of the PCB.If the wafer has ground or heat dissipation requirements, silver glue is generally used, if not, anaerobic glue is used. As the name suggests, anaerobic adhesive is to block it from contacting with the air, and it will cure naturally without high temperature baking. The use of silver glue requires high temperature baking to solidify. There are two types of baking temperature and time: 120 ° C for 2 hours, and 150 ° C for 1 hour.When choosing silver glue and anaerobic glue, pay attention to it: anaerobic glue cannot conduct electricity and conduct heat. Pay attention to its life when using. The reliability of anaerobic adhesives needs further review, and attention should be paid to the possibility of remelting.Most common COB factories belong to Low Cost, so most of them use manual mode to produce COB. Another reason is that a small amount of diverse production is not suitable for automation. There are two ways to manually pick up the die and stick it to the die pad of the PCB:5.1. Use a small vacuum pen: This type of vacuum pen is more suitable for large-sized wafers. Because the front end has a circular rubber pad, wafers that are too small will be completely covered by the rubber pads, which will affect the placement of wafers. Correctness. Also note that the metal vacuum tube cannot directly contact the wafer surface to avoid scratching the wafer.5.2. Use silicone: suitable for small size wafers. Generally, the tip of the toothpick is coated with silicone, which can be used to stick small-sized wafers to a solder pad coated with silver glue. The silver glue will stick the wafer to achieve the purpose of sticking.The silver glue applied to the pads must ensure that it adheres to 70 ~ 100% of the wafer area to ensure that the wafer does not move in the post-process. It should be noted that the silver glue should not overflow the area of the wafer to avoid contaminated solder joints. Generally, the maximum bonding rotation angle of the wafer allowed by the automatic Wire Bonding Machine is 8 ~ 10 °, while the manual wire bonding machine can allow a maximum angle of 30 °.Wafer storage: Generally, wafers from wafer manufacturers use vacuum moisture-proof packaging. If the wafer has been unpacked, pay attention to the dust contamination that cannot be exposed, and the wafer surface should not be touched by metal objects. The unsealed wafers can be repackaged in vacuum or stored in a nitrogen cabinet to avoid oxidation and any contamination.According to the shape of the solder joints, the welding process can be divided into ball bonding and wedge bonding. COB usually uses aluminum wire (Al wire) so it is Wedge Bond. Ball welding is stronger and more expensive than wedge welding.COB generally requires a manual welding machine to repair the welding wire, because the automatic machine is too expensive, if you stop to repair it will affect the output. It is generally not recommended to use PCB as the plywood, because the Wire Bonding machine has a maximum size limit, and the moving range of the Wire Bonding welding head is limited to 4 "x4". If you want to hit more than two COBs at the same time, you must Pay special attention. The COB process capability can reach a solder joint distance of 90um, but the general COB can accept a solder joint distance of 100 ~ 140um. The COB process generally only measures wire pull.7.1. Most COB manufacturers use manual dispensing, because COB belongs to Low Cost, but manual dispensing has the possibility of damaging the welding wire and the disadvantages of inconsistent dispensing shapes.7.2. The viscosity of epoxy resin is very important.7.3. Using an automatic dispenser will help control the cured shape of the COB epoxy resin.7.4. Some epoxy resins need to use preheated needles, because the epoxy resin will reduce the viscosity for a period of time after heating, which will help the epoxy resin to flow and reduce the possibility of wire pulling. The recommended preheat temperature for epoxy resin is 60 +/- 5 ° C, and the preheat temperature for PCB is 80 ° C.7.5. If the wafer pitch is relatively small (Fine Pitch), it is recommended to use a relatively low viscosity epoxy resin and use a dam (Dam) ring on the periphery to block the epoxy resin from flowing around.7.6. COB coating thanks to its quality: air foam, wire failure rate7.7. The curing time should be considered. Heal at 120 degrees Celsius for 2 hours, and 150 degrees Celsius for 1 hour. KHH curing time is (80 ' + 1hrs) + (110 ' + 2hrs)
7.8. You can choose Epoxy mixed with OK, but it should be refrigerated at low temperature.
Introducing COB LED lights from HitLights. The newest innovation in LED strip lights are now available from your most helpful LED lighting company, HitLights. If you want to know what COB lights are; how are COB strips different from standard LED strip lights; are COB strips eco-friendly; what does COB mean in LED; or when you should use COB strip lights then you are in the right place. By the end of this post, you're going to have all your HitLights COB know-how set!
What is the meaning of COB light?
COB stands for chip on board. To the average person (even most LED fans) this won't explain the COB difference. COB lights are a type of LED strip lights that appear to be one continuous, smooth light source, and the strip emits an alluring glow. The diodes of COB strips are tightly packed together along the strip, and covered with a phosphor coating which gives the COB strip its glow when lit. The COB lights can have a greater light output than standard LED lights, but otherwise share a lot of the benefits boasted by traditional LED strip lights. (Like being cuttable; energy saving; install with double sided tape.)
To give you a mental picture of the visual difference between traditional LED strip lights and COB strips, standard LED strips have a 'polka dot' effect where you can see each diode as a separate light source (the dots.) Thanks to the phosphor coating, COB lights appear the way a glow stick looks: a long, luminous smooth glow where you can't see the individual diodes of the COB unless it's dimmed to one of the strip's lowest output levels.
Have you ever seen people place diffusers on top of traditional LED strip lights to eliminate the dot look? COB lights have no need for a diffuser because they have a radiant aura already built in.
Let's talk chips for a sec. What is the chip that is referred to in the name chip on board? The diodes of LED light strips use semiconductor chips'this is where the electrical current turns into light (in broad layperson terms.) HitLights COB strip lights use what are known as flip chips'a relatively new way to position the semiconductor chips to dissipate heat more efficiently. COB lights are able to pack more diodes into each inch of strip thanks to innovations in chips and placement. More on COB advantages in a moment.
Finally, to close out the basics on what COB lights are, we must address what we know you're thinking. We didn't come up with the name 'COB' but that's the name that has stuck in the industry. And when folks talk about these lights it's 'cob' (like corn on the cob; not cee-oh-bee. Who knows? Maybe we can have an LED influencer get a cool new name like LED SuperGlow to stick. We'll let you know if that happens, but until then' back to business.)
What is the difference between COB and LED lights?
COB lights are a type of LED light, but with smaller diodes, installed closer together on the strip material, covered with a phosphor coating, appearing as one continuous glowing light when illuminated. COB lights are the latest innovation in LED lighting, which in themselves are an innovation from incandescent lights. Since COB lights are a development based off of LED technology, there are obviously many similarities. But there are also some notable differences, including appearance and style of light output, elimination of 'hot spots,' and overall brightness.
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Let's go a little deeper into some of the differences.
Energy Usage
Attention eco-friendly improvers! If you like to use greener options in your home, office, or business, you can use COB strips and go green, too. HitLights 24 volt COB strip lights are efficient to the tune of 100-110 lumens per watt. We know lots of people come to LEDs for the energy savings, Now you have even more options'like the HitLights COB light strip'without giving up energy efficiency.
Appearance & Style
Smooth, luminous, glowing, continuous'that's COB. No spots or dots, just a powerful, uninterrupted glow from the start of the strip, right to the end. If you thought LED strip lights were a pioneering product, COB strips are the next step. Advance the look of your lighting installations with COB.
Lifespan
You've heard the phrase, 'for a lifetime.' Well get ready to enjoy HitLights COB strips for a whopping 50,000 hours! If that makes you raise an eyebrow, you can rest assured with HitLights' better than industry standard 6-year warranty. We believe in our products (manufactured in our own facilities to our rigorous standard) and stand behind every strip we offer.
Other Tech Specs
Regular LED strip lights have a beam angle of about 140 degrees (the beam angle is the surface of the diode emitting light.) COB lights have a beam angle of a full 180 degrees'this in part is why the COB lights are visibly brighter. We already mentioned just how many more diodes are on COB lights than standard LEDs. How many? HitLights COB light strips offer 155 LEDs per foot. That's a lot of diodes getting their glow on!
How are COB strips and traditional LED lights similar? COB lights possess all of the benefits of all the other LED strip lighting you love. Both COB and LED strip lights are flexible, easy to use and install, and provide clear, attractive light in applications that other lights can't match. COBs are cuttable'even with that continuous flow of light that seems to be unbroken, COBs can be snipped along regular intervals on the strip. Simply look for the cut line and use simple scissors to get your COB strip to your desired length. Can COBs dim? Yes! Just like most other LED lights, COB lights are dimmable (HitLights can supply you with one of the best dimmable drivers in the industry.) For those of you who are drawn to LEDs for their green properties, COBs keep on with that tradition, being eco-friendly, too.
When it comes to the COB strip light offered by HitLights, you'll be able to choose from a warm or cool white on our bright, full of light strip (with an impressive output 360-390 Lumens per foot.) HitLight's COB strip light uses top of the line mounting tape, featuring genuine 3M double sided tape to install the lights. Shop for HitLights 16.4 ft COB strip light now, in warm white or cool white, 24 volts.
Are COB lights any good?
COB lights are pushing the innovation of LED strip lights to new, better heights. Where are some of the places you might use COB lights instead of traditional LED strip lights? Our first suggestion is to try COB lights where the actual strip will be visible (like lining a window frame or exposed on ceiling molding.) You won't need a special cover for the strips and you'll love the contemporary ambiance that emanates from the COB strips.
If you want a full lighting option, since the light output is so prominent in COB strips, COB might be your choice if you want full room lights where brightness is an asset.
Do you want to put style to the forefront? If you are trying to create a certain cool, modern, or high-style look with your lighting, COB works in these applications, too. Lighting with an aura like COB radiates creates a look and feel that is of the moment, and maybe even a little futuristic.
You don't have to wing it with any of our lights or products'including our new HitLights COB strips in either warm white or cool white. One of our team members is ready to answer any of your specific COB questions. We're ready to help you plan and achieve all of your COB home improvement projects. Our tech team is ready to talk you through any application of our products.
If you are looking for a COB lighting supplier or custom COB lighting to serve your needs, our PRO team wants to talk to you. Learn more about our PRO Accounts at HitLights and if PRO is right for you and your business.
COB strip lights are a wonderful option for home use or in your business or commercial locations. We are excited for the future of LED lighting, and our new line of COB lights are a key element of that future. If you are intrigued by the look or performance of COB strip lights, we encourage you to try one today and we know you will love them as much as we do.
If you're ready to glow up, get that COB going'call us today. We would love to hear about how you are using these new COB lights. Questions? Call us now at 1 (855) 768-. to get the assistance you need. HitLights is ready for COB or any LED projects you have. Ready, set, glow!
The company is the world’s best are cob lights better than led supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.