From the Courtesy of ASM Pacifc Technolgy Ltd Web Site.
From Courtesy of VisEra Web Site
As what I had previous mentioned, after almost a year, we can visualize that the HB LED has more or less established an industrial standard for a package size of approximately in the range of 3mmx 3mm to 3.45 mm X 3.45mm with height 2mm to 2.6mm By the major players Cree, Osram, Seoul Semi, Nichia, Edison, VisEra…
These will be one of main stream of the HBLED in the coming 5 years at least as these would have certain advantages such as high volume manufacturability, small foot print, high lumen output, Good thermal performance, SMD compatible, high reliable, reasonable good cost structure.
The Market Demand
In order to put a high power LED chip onto ceramic substrates, we need to ensure that there is no void under the die attaches media such as High silver content epoxy. The epoxy coverage has to be even, and the process control of the dispensing, stamping method has to ensure that the total void should be less than 10% and single void should not be larger than 5%. Thus to avoid “Hot Spot” of the LED during light up operation.
High Density Manufacturing
If we have formed a standard size of say 3mmx3mm footprint, we have to determine the suitable panel size for the ceramic substrate.. Base on today technology, the panel size has to be large enough as the larger the ceramic panel the lower the cost of it as due to reasons of the tooling availability, the efficiency. Now the optimized size such as panel of size 100mmx100mm. That would be a challenge not to create too much warppage, the best industrial product can achieve warp page less than 0.3% of the width of the panel. That is approximately 12 mil of a 4 inch panel. With a 4 x4 inch panel, typically we can obtain about 1,000 HBLEDs. Some smaller Chip Scale LED can even come up with almost 2,000 LED on one Panel.
Liquid Silicone Molding for the Dome lens
It will be the main stream for LED lens using Silicone molding method for certain advantage of Consistency in lighting after years, Silicone material is stable and will not change colour. The Lighting resistance is low. One mould shot can build all the lens on each of the every LED on the ceramic substrates. There is a way to ensure that the Optical centre is aligned with the LED die centre, where by there is a demand to have the Die bonder to have certain alignment method to be same as the down stream molding process. The Die bonder has to perform Ceramic Panel Global alignment on two edges on for 3 or 4 alignment points before the commence of the die bonding.
Challenge on the Die Bonder Accuracy
There is a need to have diode, TSV, or EDS die to be built onto the tiny space of the 3mm x3 mm ceramic substrate there is tough challenge on he epoxy dispensing. As well the 1mmx 1mm HB LED chip has to be living in the tiny House of the cavity with the Diode. The die placement and die rotation has to be better the+/- 38 microns +/-1 degree, under a process capability CpK>1.67! The basic die bonder should have a capability to achieve a die placement of +/- 15 microns. At three sigma for certain Applications.
Challenge on the Ceramic Panel Handling
Since the panel is thin as 0.3mm under a perimeter of 100mm x100mm, that is fragile and easy to be damaged if the Die bonder design is not able to provide a Smooth transportation on X and Y and Z axes. Well there are ways to do that, either using old fashioned way of belt transportation to transfer the panel from the input magazine into the dispensing stage and then Bonding stage for bonding before passing thought to the output stage. There is way to apply vacuum or mechanical clamping to hold the thin panel, but that should be having soft touch and jam detection or there will be disasters. Imagine that the whole panel is bonded with 1,000 LEDs and during the transportation at output side, there is a mis-placed magazine that would crack the whole panel! The LEDs, Epoxy, ceramic panel will cost over a few hundred Dollars!
New Generation Die Bonder for LED
In The Market, there is a new Die bonder, that has all the above challenged being tackled, plus
Patent pending Work Holder that would have a smooth Transportation of the ceramic panel with theoretical 0.1 mm Thickness without any Damages. Carrier Free operation, another twenty features such as Magazine Tilt detection, Magazine Orientation detection, Panel Position Detection, Ceramic height profile detection for Epoxy and bond stage. With Full Post Epoxy and Post bond inspection system. Least but not last Die Placement and Rotation process detection.
With an UPH of more than 8,000 with most the above feature being switched on…
This is ASM AD838L new generation Die Bonder for HB LED application.