How to smear thermal grease correctly

With the promotion of computer performance, power consumption of CPU is increasing constantly. Due to technology improvement, the power consumption has been alleviated, but because of the enhancement of graphics performance, CPU power consumption is proportional to its performance. Therefore it is still a worthy of our attention that the power consumption is too large to result in higher temperature. Now there has been a very high degree of concern about the heat dissipation problem, however, the majority of consumers simply consider big CPU radiator can solve the dissipation problem. In fact, this idea is very one-side because except for CPU and heat radiator, thermal grease is also very significant and cannot be ignored in the aspects of solving CPU heat dissipation problems.

For many people, thermal grease may not be very striking thing, but it is a very significant link between CPU and radiator. If the way of installing and smearing is not correct, it will lead the temperature of CPU to increase and can even result in the device damage. Thus it is very important to smear thermal grease correctly. There are two main ways, as shown in the following figures: one is that a little grease is squeezed in the center of CPU/GPU surface, and then it is extruded evenly by a radiator; the other one is that the thermal grease is smeared on the surface of CPU/GPU by a finger. The first method is suitable for a relatively small surface area and the second one is more suitable for a larger area.

Fig. 1. The first smear method

Fig. 2. The second smear method

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NTC thermistor (II)

II. The performance of thermistor

With higher and higher precision requirement for temperature measurement and more and more harsh measurement environment requirement, high stability and precisionthermistor has been developed and produced. This kind of thermistor has compact size, wide resistance, high precision, and short response time.

III. The development of thermistor

As the thermistor in high temperature application, it shall has the following conditions:

a. Thermistor material is stable; electrode material is stable, with high density, and is connected closely with the lead.

b. Thermal expansivity of the thermistor, the lead and packaging materials match.

c. The lead and packaging material are stable.

d. The packaging material has good insulativity in high temperature.

e. Heat and shock resistance, and reliability.

High precision high stability NTC thermistor is mainly applied for temperature control and measurement for xerographic printer, automation equipment, thermal printing heads, furnace and water heater. In recent years, NTC thermistor has been used in automobile in a new way. It’s used in electronic oil injection system of automobile motor for measuring the temperature of the exhaust gas in order to improve fuel utilization.

To be continued…
A number of thermistors are provided here in ATI.

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NTC thermistor (I)

In industry and agriculture manufacture, national defense, scientific research and office equipment automation fields, temperature is a very critical data. Temperature sensor, i.e. thermistor is a kind of sensor with repeatability and regularity. Among all the temperature sensitive components, thermistor holds a very important position, accounting for 40% of the total temperature sensitive components. According to the characteristics of resistance change with changes in temperature, there are two types of thermistor: NTC thermistor and PTC thermistor. The former resistance decreases when the temperature rises, while the latter resistance increases when the temperature rises. We’d like to focus on NTC thermistor.

I. R&D for NTC thermistor

Common NTC thermistor is made up of 2~4 transition metal oxides like Mn-Co-Ni-Fe-Cu, with ceramic sintering process. The characteristics of the thermistor is closely related to the ratio of the metal oxides, sintering conditions, and annealing conditions. One of the most important characteristics of NTC material is that resistivity ρ and B value remain the same in a quite wide range, which guarantees the consistency of products. However, when we select suitable material, NTC material is affected by material stability, sintering, consistency, thermal expansivity of the material and auxiliary material, and the cost. In order to improve the stability and working temperature of NTC thermistor, add chromium hemitrioxide, zirconium oxide, aluminium oxide or SiC into transition metal oxide to control the resistivity ρ and B value.

To be continued…

We provide various NTC thermistors with or without lugs.

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Operation points for NTC thermistor

NTC thermistor is a sensor, which has been widely used in the applications of temperature measure and control. NTC thermistor is small in size, with  fast response speed. However, users need to pay attention to the following points when using NTC thermistor.

1. NTC thermistor can withstand thermal shock of 200℃,but in order not to make thermal diode aging, the rapid changes should be prevented as far as possible for the packaging material is glass.

2. When the current is going through the thermistor, self-heating and temperature difference will be caused, which we need to consider before using.

3. Due to defective insulation and electrostatic induction, false wiring can cause that the current flowing through the thermistor is too large to damage the thermistor. Therefore, ensure there is no overcurrent through the thermistor in wiring mode.

4. For the system with high precision requirement or without thermistor resistance aging, we should use a high reliability thermal diode after high temperature testing. The circular thermistor that is often used for temperature compensation in a circuit, cannot be used in the system with variable characteristics.

5. In order to prevent heat leakage and temperature errors, we need to use the maintenance pipes, metal pipes or nonmetal pipes.

6. When there are water droplets, dust or ionic compounds surrounding the thermistor, it can lead to decrease of the resistance or measurement error, so the thermistor should be moisture-proof and insulation disposal so as to maintain itself drying.

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Mini USB color camera

ATMC102U is a kind of mini USB color camera, which has been widely used for medical care, microscope, video conference, video phone, multimedia computer toys, industrial pipe and bottom inspection, CCTV safety supervision and other applications.

There are two parts in this camera: a camera head and an USB video converter.The former has analog video / audio output signal and it is easy for the latter to connect to the computer, which can convert analog signals into digital signals.Between the two parts, there are 4 metal wires.The camera head has all of circuits, which can generate standard NTSC or PAL video / audio signals.The image sensor has a built-in color filter array, used to generate color signals.

Features

Small installation hole: 2.2mm

Compact size: 11×11×7 (mm)

Plug and play: no need to drive

High sensitivity: 0.6 lux/F1.2

Progressive scanning

High signal to noise ratio: > 50dB

Weak current: < 100mA@5V camera head 2

High resolution: 640 * 480

Analog video / audio output

Through the USB port output

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Our web site is http://www.analogti.com

Laser power supply

Laser power supply is designed to driver high current laser diodes. The output current 0-45A can be set by the analog voltage 0-2.5V. The output voltage 0-3.5V or 0-5V can also be set. In addition, our company has a professional design team and production workshop, so we can customize products for meeting customers’ general and special requirements. I will introduce one kind of laser power supply.

Laser power supply 20A5V

High efficiency: ≥ 76%

Maximum output current: 20A

Output voltage range: 0V ~ 5V

Input voltage range: 88VAC ~264VAC

High speed digital modulation: 5 KHz

The output voltage and current limit can be set

Digital valley current can be set

Low temperature: 35°C

Over temperature protection

Working temperature: −20°C ~ 50°C

Compact size

Low cost

100% Lead (Pb)-free and RoHS compliant

If you are interested in our products, please feel free to contact us.

Our web site is http://www.analogtechnologies.com

Laser diode

Laser diode is mainly made up of semiconductor materials, thus it is also called semiconductor laser, with features such as high conversion efficiency, wide band range, long service life, direct modulation capability, compact size, light weight and low cost, etc.

Like most of lasers, laser diode has the same working principle, i.e. stimulated emission. The difference is that the electrons of the laser diode are distributed in different energy states of different energy bands, while the particles of other lasers are distributed in different energy states of active media. Therefore, there is a difference in particle numbers inversion.

Laser diode current

There are two critical diode currents: threshold current and transparency current. The former stands for the forward current when reaching the threshold gain and the latter refers to the injection current when the stimulated radiation is the same as absorbing  below the threshold value. At this time, the material absorbs no net photon, which can be seen as transparent. When the current is below the threshold current, the output of the diode is spontaneous radiation, with low power, like LED. When the current is more than threshold current, and cavity gain reaches threshold gain, laser oscillation forms.

In order to properly drive the laser diode, a laser driver is needed. Nowadays, compact sizelaser driver is more and more popular among electronic engineers

You may visit this page for more details of laser controller:

http://www.analogtechnologies.com/laserdriver.html

he working principle of DC-DC step down converter circuit

Switching power supply can be divided into isolation and non-isolation circuit. In this paper, we will focus on the non-isolation circuit. According to different circuit forms, it can be divided into buck circuit, boost circuit, buck-boost circuit, cuk circuit, sepic circuit and zeta circuit. Here, we mainly analyze the working principle of DC-DC step down converter circuit. As shown in figure 1, power MOSFET is an adjusting switch element and its turn-on and turn-off are determined by the control circuit. L and C are filter elements. When switching off, the diode VD can keep the output current continuous so that it is known as fly-wheel diode. When the output signal of control circuit switch on VT, the current in filter inductor L will increase gradually and the capacitor C will start to charge. Ignoring conduction drop of MOSFET, its source voltage should be Uin.

Fig. 1. The main circuit of buck DC-DC converter

According to design of TL494 (single ended buck DC-DC converter) and using continuous current mode, when the switching power supply works on CCM, the turn-on time is DT and Ii uplift amount is [(Uin-Uo) *DT]/L in a period; the turn-off time is (1-D)T and Ii uplift amount is [(Uin-Uo) *DT]/L. In the steady state, the two working principles from the top surface of the non-isolated circuit can make ILequal at the end and begining of each cycle. So the following expression can be obtained.

Sothe relationship of duty ratio D, Uin and Uo is as follows:

Fig. 2 is the main waveform of CMM buck type switching power supply.In every period, the charge transferred by ILis the same with the charge got by Io at the same time.

Fig.2. TheCMM waveform of continuous current mode

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The advantages and disadvantages of TEC modules (II)

We mentioned that do not power the TEC modules for a long time when there is no heat sink.

Here is the right installation method:

A. Install a heat sink in one side of TEC module, while the other side installs a thermal load. The installation surface flatness is less than 0.03mm. Remove any burrs or pollutant.

B. Make sure a good contact between TEC module and Thermal load, as well as TEC module and heat sink. Thermal conductive pad needs to be put in the contact surface.

C. Fix the TEC module with proper stress so as not to damage the TEC.

Operation conditions:

1. The voltage of DC power supply doesn’t exceed default voltage of the TEC modules. The ripple coefficient is less than 10%.

2. The current cannot exceed default current.

3. When the TEC is working, do not reverse the voltage instantaneously. Reverse the voltage after    5 mins.

4. The ambient humidity cannot exceed 80%.

Visit us for more details about the TEC modules and its controller.

For more information, please visit our website:For more information, please visit our website:http://www.analogtechnologies.com/tec-module.html

The advantages and disadvantages of TEC modules (I)

TEC modules (thermal electric cooler), also called Peltier modules, can cool down or heat up the object when changing the current direction. The current is DC current. There are some advantages and disadvantages of TEC module.

Advantages:

A. No cryogen needed. TEC modules can work constantly for hours. It contains no pollution or rotating components, which results no noise and vibration, long life span and easy installation.

B. Very short heating-up and cooling time due to small thermal lag in TEC modules. The max. temperature difference will be achieved within one min, under the condition of good hear dissipation in hot side and no load in cold side.

C. Thermal electric cooler is a kind of current-to -energy device. By controlling the current, high precision temperature control can be achieved. Plus temperature measurement and control, it is easy to make a automatic control system with the function of remote control, program control and computer control.

Disadvantages:

A. Single TEC modules has small power. Combine them to thermopile and then cascade or parallel these thermopiles to be a cooling system with high power, from 1mW to10KW.

B. The hot side temperature should not exceed 60°C, or it may be damaged. Do not power the TEC modules for a long time when there is no hear sink. Make sure there is enough heat dissipation devices for TEC modules.
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The working principle of LED lamp and the important role of LED controller

LED lamp usually contains a LED array. According to the preset program, LED controller can control the switch at each position in the LED lamp circuit and lighten LED regularly to show a specific text or graphics. LED lamps connect together in series, and they should be driven by a constant power supply.  When using, the current control needs to be strict in order to ensure the LED lamp work normally for the brightness of each LED is determined by current.

The pictures of LED lamp and LED controller

The working principle of LED lamp is simple. The current is through a compound semiconductor first, and then by a combination of electrons and holes, the excess energy will be released in the form of light so as to achieve the lighting effect. The brightness of LED lamp is determined by the forward current. In order to achieve adjustable light, LED lamps should take a unidirectional adjustment. In this case, some problems may occur in LED controllers, such as slow start speed, uneven illumination and so on. It is a little difficult to ensure the LED controller work normally when adjusting light.

In our company, we not only have LED lamps and LED controllers but also have LED related products. And we have our professional design team and production workshop. Our honor is to provide customers with superior quality and convenient services.

If you are interested in our products, please feel free to contact us.
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Chip capacitor and its application

SMT capacitors are famous for high stability, reliability and precision in IC design and have been widely used in many electronic fields.

Chip capacitor can eliminate high frequency interference produced by itself, so that other chip modules will work well without any interference. In high frequency electronic oscillation circuit, chip capacitors and crystal oscillator form a oscillation circuit, which provides clock frequency for various circuits.

Chip capacitor has different sizes, 0402,0603,0805,1206 are the most popular sizes.

For managing and storing so popular capacitors, a simple way is provided by ATI, i.e. SMT Capacitor Kits. This capacitor kits have 128 individually lidded coverlets and a top cover. Capacitors are stored in these coverlets beforehand and users can get any capacitors easily with tweezers.

Similar kits like Resistor kits and Inductor kits are also available in ATI websites. If you’d like to manage the chips by yourself, you can simply get a empty enclosure and distribute the chips in the coverlets by yourself.

To know more kits, please visit us at: http://www.analogtechnologies.com/ 

SMT inductors and SMT inductor kits

SMT inductor is also called power inductor or high current inductor. The SMT inductor can be divided into two types: one is with magnetic cover, the other one  without magnetic cover. In a circuit, SMT inductor mainly has the functions of filter and oscillation.The inductor has the advantages of miniaturization, high quality, high energy storage and low resistance. Therefore, our company (ATI) has designed and manufactured SMT inductor kits to storage the inductors as in the following picture. And SMT inductor kits can save a lot of time to find the inductors and simplify the management of complicated components. They are very popular among electronic designers and users.

The pictures of SMT inductor kits

Next I will mainly introduce SMT inductor kits.

The inductance range of SMT inductor: 0.6nH~1000uH

Packaging forms: 1008、0805、0603、0402

Outside dimension: 280mm*(length) 210(width)*40(height)

Inside dimension: 15mm*(length) 22(width)*16(height)

There are corresponding inductance value, resistance value and current value printed on the each small box lid. The design of each small box lid is very exquisite, and the handle feeling is also very good. After opening, it is convenient to take one inductor with tweezers. Except for SMT inductor kits, we also manufacture SMT resistor kits and SMT capacitor kits, which are all US-parented products. You can select what you need.

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LED Driver

LED driver is an electronic device, which is used for driving LED to light or LED modules to work normally. Due to conduction characteristics of LED PN junction, the LED driver can only adapt to a narrow variable range of the supply voltage and current. If the range changes a little, it will lead that LED may not be light up, the luminous efficiency will reduce seriously, the LED’s service lifetime can be shorten, or even the chip can be damaged. A fundamental frequency power supply and common battery power supply are both not suitable for supplying LED directly, however, LED driver can make LED work normally in a good voltage and current state.

In practical application, according to work characteristics, LED driver can be divided into two types: DC power supply driver and AC power supply driver

1. DC power supply driver

According to different applications, DC power supply driver can be divided into three types: DC buck driver, DC boost and DC converter driver.

2. AC power supply driver

Using city power, it can also be divided into three types: buck, boost and converter driver according to different applications.

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Our web site is http://www.analogtechnologies.com/

Evaluation Board TECV104 for TEC Controller TECA1-5V-5V-D

TECV104 is an evaluation board of ATI, which is composed of a complete tune and function circuit, to drive TEC controllers. The evaluation board can set the output current limit and the internal operating temperature. There is a LED light that can indicate the TEC temperature state; in addition, there are also a plurality of connecting pieces for connecting the external components and instruments.

TECA1-5V-5V-D (no compensation network) is designed for TEC with 2A low noise current. When powered by a 5V power supply, the range of output voltage is from 0V to 5V. It is easy to use TECEV104 to evaluate TEC controller. If you read the TECV104 specification with TECA1-5V-5V-D’s, that will be a good selection because the specification of TECA1-5V-5V-D can provide some relative information.

The main purpose of using this evaluation board is for tuning external compensation network in order to match the characteristics of thermal load. What is more, it can also minimize the response time of thermal control loop and the tracking error of dynamic temperature, whilst the control loop can keep in stable.

Users can set the maximum output voltage and target temperature. You can also monitor the output voltage and the actual heat load temperature.

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Resistor/capacitor/inductor kits

SMT kits are the independent research and development product of Analog technologies, Inc. SMT kits are US-patented product of ATI. Because of its convenient management, the users can save a lot of time investigating, purchasing and searching for electronic components. Therefore, they are so popular among electronic designers.

1. Resistor kits

SMD resistor, 1% precision, resistance range of 0~20M;

Packaging forms: 1026, 0805, 0603, 0402;

Each small box cover has the corresponding resistance value;

The resistor kits are divided into two series, E24 and E96, and they include 128 and 510 kinds of resistances respectively.

2. Capacitor kits

SMD capacitors, NPO/X/R/X5R, capacitance range of 0.5pF~22uF;

Packaging forms: 1008, 0805, 0603, 0402;

There are capacitance value, material, precision and pressure value printed on the each small box lid.

3. Inductor kits

SMD inductors, inductance range of 0.6nH~1000uH;

Packaging forms: 1008, 0805, 0603, 0402;

There are inductance value, current, precision and impedance printed on the each small box lid.

If you want to know more, please click here: http://www.analogtechnologies.com/

Brief Introduction of Drive Mode of The Laser Driver

The incentive method of laser drivers is mostly injection current form. When the injection current is greater than the threshold current, radiation power will rapidly rise with the increase of the current. Therefore, by changing the injection current, the output optical power can be adjusted. In order to control semiconductor laser, the methods of automatic control are usually adopted, which includes constant current/power/voltage control.

In the constant power control mode, by using photoelectric detector, a small portion of laser power can be received and transformed into monitor current. Then after the monitor current is through the current to voltage convertor, a closed loop negative feedback control will be formed by comparing feedback network of constant power control with a set value. Due to the influences of temperature or other factors, the laser output power will change, and the negative feedback can control the optical power to keep stable.

In a special situation, constant voltage control is very simple and useful. When the drive voltage is constant as demanded, this mode will be selected.

In the constant current control mode, by current sampling and feedback, the current driving unit is provided active control and can make the current drift minimum. When cooperating with temperature control, the using effect will become better.

Now constant current control is usually adopted because semiconductor laser devices commonly use constant current source.

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The difference between TEC and TEG

As shown in the fig1pictures below, there are little few appearance differences between TEC and TEG, but their principles and applications are not the same.

Fig 1. The photo of TEC and TEG

Based on semiconductor materials, a thermoelectric cooler (TEC) can be used as an electronic component of a small heat pump. Through by adding a little low DC voltage to both ends of TEC, heat quantity will flow from one end to the other, and at the same time, the temperature of one end will decrease and the other end will rise. It is noteworthy that as long as the current direction is changed, the heat flow direction will also be changed, so one piece of TEC can simultaneously achieve two functions: cooling and heating. And TEC can be used for precise temperature control.

A thermoelectric generator (TEG) is based on “Seebeck effect” to concert transform heat into electricity directly. In an open circuit with two different conductors, if there are temperature differences between its two contacts, this circuit will produce electromotive force, meaning that with the temperature gradient moving from high temperature region to low temperature region, thus the thermal electron in an object can produce electric current or charge accumulation.Therefore, TEG can be used for power supplies of radios, televisions, tape recorders, computers, and some other devices.

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Introduction of Epoxy Resin

Epoxy resin refers to organic compounds with two or more epoxy groups, and with rare exceptions, their relative molecular mass is not high. Epoxy resin has many advantages such as good dielectric properties, mechanical properties, adhesion, corrosion resistance, etc. And its dimensional stability and manufacturability are also both good, as well as its comprehensive properties. What’s more, due to the flexibility and diversity of epoxy materials, epoxy resin almost meets all the requirements of various special properties of epoxy material, so it is widely used in the field of electronic appliances.

The main applications of epoxy resin in the electronic fields: pouring materials of electric power transformers, transformers, insulators and other electric appliances,  encapsulating materials of electronic devices, plastic packaging materials of integrated circuits and semiconductor element, circuit board and copper clad laminate materials, insulating paint of electrical and electronic products, insulating adhesive, high voltage insulator mandrel, and so on.

There is an example of epoxy resin, ATEE2850, which is a double-component, thermally conductive epoxy with low coefficient of thermal expansion, excellent electrical insulation properties and high thermal conductivity, long service lifetime after opening, good chemical resistance, etc. If you are interested in our products, please contact us.

Our website is: http://www.analogtechnologies.com/