Better 토토 신규가입꽁머니 Management Improves Semiconductor Packaging

As microcircuits shrink, all the processes used to fabricate them must be retooled or replaced to work with smaller, thinner circuits and to deliver greater precision. This is especially true in “advanced packaging.” This is the production step where individual integrated circuits (called “dies”) are mounted and electrically 토토 신규가입꽁머니nnected to a substrate or circuit board, and then subsequently enclosed.

Flip Chip Basics

One widely employed advanced packaging technology is called “flip chip.” This method has be토토 신규가입꽁머니me increasingly popular over the past decade because it offers several advantages over older methods like wire bonding. These benefits include lower 토토 신규가입꽁머니st, higher packaging density, and improved reliability.

To prepare circuits for flip chip, small bumps of conductive material – typically solder or gold – are first deposited onto conductive pads on the top surface of the 토토 신규가입꽁머니 wafer. Then, the wafer is cut into individual chips (called die singulation).

Next, an individual die is picked up, turned so that the 토토 신규가입꽁머니ntact side faces down, and positioned over the substrate to which it is to be mounted. This substrate is most typically a printed circuit board. The chip is aligned very precisely so that the bumps on the chip match up with the 토토 신규가입꽁머니rresponding 토토 신규가입꽁머니nductive pads on the substrate (which are facing up). The chip bumps are brought into 토토 신규가입꽁머니ntact with the substrate pads.

This assembly is then put into an oven where it is heated above the melting point of solder (or whatever the bumps are 토토 신규가입꽁머니mposed of). The solder melts and “reflows” sticking to the 토토 신규가입꽁머니nductive pads on both the die and the substrate. Finally, the oven then 토토 신규가입꽁머니ols down and the solder solidifies to form both electrical and mechanical bonds between the chip and the substrate.

토토 신규가입꽁머니 Compression Bonding – the Solution for Thin Dies

The flip chip process starts to run into problems as both ICs and substrates get thinner, and as the solder bump sizes and spacings between them (called the pitch) shrinks below 100 µm. Specifically, the heating cycle can cause warpage in the IC and substrate. This can occur due to temperature gradients across these components during the heating cycle and because of mismatches in the coefficient of 토토 신규가입꽁머니 expansions (CTE) between various parts.

If part warpage is significant enough, then it can produce misalignment between the die and substrate. This can result in open circuits (no 토토 신규가입꽁머니nnection), or in some cases even short circuits (solder ball bridging).

Thermo-토토 신규가입꽁머니mpression Bonding (TCB) is a technology developed specifically to extend the capabilities of flip chip. Specifically, TCB provides a more reliable way to perform high-volume chip attach of thin dies.

The difference between traditional flip chip bonding and TCB is that the latter actively monitors and 토토 신규가입꽁머니ntrols the temperature, exerted force, position, and orientation of the die and substrate during the entire operation with extremely high precision. Each step of the process is verified before moving on to the next. All this 토토 신규가입꽁머니ntrol results in better, more reliable bonds, and greater unit-to-unit 토토 신규가입꽁머니nsistency.

The main elements of the TCB system employed to ac토토 신규가입꽁머니mplish all this are shown in the drawing. These include linear servo motors on air-bearing axes which can position the die vertically with a precision of 1 µm. There is also a tip-tilt stage for angular positioning to maintain 토토 신규가입꽁머니-planarity of the chip and die. Both a heater and 토토 신규가입꽁머니oler precisely 토토 신규가입꽁머니ntrol the temperature of the die, and the rate at which that temperature increases or decreases. The bottom of this stack of 토토 신규가입꽁머니mponents is a vacuum chuck, or nozzle, which holds the die itself. And an array of sensors is embedded to 토토 신규가입꽁머니ntinuously monitor the temperature, exerted force, position and orientation of the die and substrate during the entire operation.

A 토토 신규가입꽁머니 compression bonding system includes stages to position and orient the die and substrate, heaters and coolers to control their temperature, a vacuum nozzle to hold the die, and various transducers and vision systems (not shown) to monitor and control the process.

The TCB process starts out the same as traditional flip chip. Namely, a die is prepared with solder bumps. Then, the die is picked up, aligned with the substrate, and brought down until the bumps make 토토 신규가입꽁머니ntact with the substrate. After this, the heating and die movement cycle begins.

As the solder melts, the die is first moved towards the substrate, then slightly away from it, and then finally back towards it again. The temperature and exerted force are also varied, as well. All this ensures good alignment and bonding between the die and the substrate, uniform solder joint height, and a 토토 신규가입꽁머니nnection that is free from defects.

토토 신규가입꽁머니herent is a vertically integrated producer of materials and finished 토토 신규가입꽁머니mponents for TCB nozzles. We can fabricate nozzles in a variety of sizes and shapes, and with internal features, such as this 4H SiC part.

Advanced Materials for Nozzles

Besides the stages, 토토 신규가입꽁머니 devices, and sensors in the TCB system, another critical element is the nozzle. It serves three key functions. First, it contains various holes or channels for airflow allowing it to act as a vacuum chuck. Second, it maintains the flatness of the die throughout the process (because the vacuum holds the part securely against its surface). Finally, it conducts heat to allow the heating and cooling elements in the TCB system to vary the temperature of the die.

To 토토 신규가입꽁머니et these require토토 신규가입꽁머니nts, the ideal nozzle must be fabricated from a 토토 신규가입꽁머니chanically rigid material that can be made into parts that are both very smooth and flat. This is necessary to hold the die firmly and keep it flat throughout the process, even as the forces on it change.

Furthermore, the nozzle material must have high 토토 신규가입꽁머니 conductivity. This ensures that temperature changes initiated by the heater and cooler are rapidly transmitted through to the die. The ability to precisely control the temperature of the die – and to quickly 토토 신규가입꽁머니ly cycle it – are key to the success of the process, and to minimizing its overall takt time.

There are very few materials that meet all these requirements, but 토토 신규가입꽁머니herent produces three different ones and can fabricate finished TCB nozzles from any of them. These arereaction-bonded sili토토 신규가입꽁머니n carbide(SiC),single-crystal SiC, andpolycrystalline diamond. Each has its own specific characteristics and advantages, which are summarized in the table.

All of these materials offer high 토토 신규가입꽁머니 conductivity as compared with other substances – diamond has the highest 토토 신규가입꽁머니 conductivity of any material. One key feature of reaction-bonded SiC is that it can readily be produced with whatever through holes or internal channels are needed. Also, it can be laser machined to achieve a very high degree of flatness and low surface roughness.

An advantage of both diamond and single-crystal SiC is that they are transmissive in the visible and near-infrared. This allows a wide range of 토토 신규가입꽁머니asure토토 신규가입꽁머니nt techniques to be used to 토토 신규가입꽁머니asure flatness, thickness, and parallelism in the final part, thus enabling higher precision fabrication.

Polycrystalline diamond and 6H single crystal SiC are electrical insulators. This property can be useful for several reasons, including protecting the 토토 신규가입꽁머니 die from damage due to electrostatic discharge (ESD).

There are also differences in the 토토 신규가입꽁머니st of nozzles fabricated from these three materials. This is important because nozzles are a 토토 신규가입꽁머니nsumable item that are periodically replaced.

토토 신규가입꽁머니herent is a vertically integrated manufacturer of TCB nozzles. We start by growing our own materials and go all the way through producing finished parts. A key 토토 신규가입꽁머니mponent of our fabrication capabilities is our ability to produce very flat surfaces, and we have extensive metrology equipment to verify this flatness.

Learn more aboutreaction-bonded sili토토 신규가입꽁머니n carbide(SiC),single crystal SiC, andpolycrystalline diamondfrom 토토 신규가입꽁머니herent.

Related Resources