How to strengthen BGA to prevent cracking

The circuit board deformation usually comes from the rapid heating and rapid cooling caused by high temperature reflow soldering, coupled with uneven distribution of parts and copper foil on the circuit board, so the deformation of the circuit board is worsened. Then, how to strengthen the circuit board BGA circuit board to prevent cracking it?

Method for increasing deformation resistance of circuit board:

* Increase the thickness of PCB
If possible, it is recommended to use more than 1.6mm of the thickness of the circuit board,

* Use high Tg PCB material
High Tg means high rigidity,

* Put steel around BGA
If there is space, think about it, like building a house, put steel around BGA.

* Fill the circuit board with Epoxy glue
Also consider glue around the BGA or the back of the corresponding circuit board, to strengthen its resistance to stress.

Reduce the amount of deformation of PCB:

Generally speaking, when the circuit board (PCB) is assembled to the chassis, it should be protected by the casing, but because today's products are becoming thinner and thinner, especially handheld devices, the circuit board is deformed by force.

Reduce the deformation caused by an external force on a circuit board, there are the following methods:

*Increase the buffer design of the mechanism to the circuit board

*Insert screws or positioning mechanisms around the BGA.

*Strengthen the case strength to prevent it from deforming and affecting the internal circuit board

Enhance the reliability of BGA

*Pour glue at the bottom of the BGA.

*Increase the size of the BGA pad on the circuit board

*Using SMD layout

*Using Vias-in-pad design

*Increase soldering capacity

*If it's already finished, It is best to use "Stress Gauge" to find the stress concentration point of the circuit board.

Eight kinds of PCB surface treatment process

With the continuous improvement of human living environment requirements, the environmental problems involved in the PCBproduction process are particularly prominent. The topic of lead and bromine is the hottest, Lead free and non halogenated will affect the development of PCB in many ways.

Although for now, The surface treatment process of PCB has not changed much, But it should be noticed. Long periods of slow change will lead to dramatic changes. In the case of increasingly high environmental protection voices, The surface treatment process of PCB will certainly change greatly in the future.

The basic purpose of surface treatment is to ensure good solderability or electrical properties. Because copper in nature tends to exist in the air in the form of oxides, unlikely to remain as raw copper for a long time, So copper treatment is therefore necessary.

here are many PCB surface treatment processes now, following will be introduced one by one:

* HASL
Hot air leveling, also known as hot air solder leveling (commonly known as tin spray), It is the process of coating molten tin (lead) solder on the surface of PCB and blowing (blowing) flat with heated compressed air, and make it a layer that is resistant to copper oxidation, and supply coating with good solderability. During the hot air, solder and copper combine to form copper tin intermetallic compounds.

* OSP
OSP also called Organic Solderability Preservatives, Simply speaking, OSP is on the surface of cleaning bare copper, chemically grown a layer of organic film. The film has oxidation resistance, heat shock resistance and moisture resistance. Used to protect the surface of copper from corrosion in the normal environment.

* Full plate nickel plated gold
The gold plated nickel plate is plated with a layer of nickel on the surface conductor of PCB and then plated with a layer of gold. Nickel plating is mainly to prevent the diffusion of gold and copper. Soft gold is mainly used in chip packaging gold wire. Hard gold is mainly used in non welding electrical interconnections.

*  Immersion Gold
The gold is a thick, electrically charged nickel alloy on the copper surface. this can protect PCB for a long time. In addition, it has the environmental tolerance that other surface treatment processes do not have. Immersion  gold can also prevent the dissolution of copper.

* Immersion Tin
Since all solders are based on tin, the tin layer matches any type of solder. Tin deposition process can form a flat copper tin intermetallic compound.

* Immersion silver
The silver deposition process is between organic coating and electroless nickel plating / immersion, the process is simple and fast. Silver can still maintain good solderability even when exposed to heat, humidity, and contamination.

*Electroplated hard gold

In order to improve the wear resistance of products, increase the number of plugging and electroplating hard gold.

Cause analysis of PCB price difference

The cost of the PCB industry is the most extraordinary and complex of all industries, from the opening, platen, forming, until the FQC, packaging, finished warehousing. According to the cost of each process inputs, labor costs, manufacturing costs, such as step-by-step accounting, Then, according to the order product number, the cumulative cost. All of these affect the calculation and evaluation of WIP cost and scrap cost directly.

First, different materials used in PCB result in price diversity.

Materials are generally FR-4, CEM-3 and so on, thickness ranges from 0.6mm to 3.0mm. Copper thickness varies from Oz to 3 Oz. All this creates a huge price difference on the sheet metal.

Second, The diversity of manufacturing processes used by PCB creates price diversity.

Different production processes lead to different costs.

Third, the price diversity caused by the difficulty of the PCB itself.

Even the same material, the same process, But the PCB itself is difficult and creates different costs. 
The difficulty of the retirement rate is higher, and Inevitable cost increase, And then create price diversity

Fourth, Different customer requirements can also lead to price differences. 
The level of customer requirements will directly affect the rate of finished products in the factory, Such as a board according to IPC-A-600E, Class1 requirements have 98% pass rate, but according to class3 requirements may be only 90% of the qualified rate, resulting in different costs of the board factory, and finally lead to variable product prices.

Fifth, Price diversity caused by PCB manufacturers.
Even with the same product, but because different manufacturers, process equipment, technical level is different, but also the formation of different costs.

Sixth, Price differences caused by different payment methods

At present, the PCB board factory will adjust the PCB price according to the different payment methods, the range is 5%-10%, which makes the price difference.

Seventh, Regional differences lead to price diversity.

At present, the domestic geographically speaking, from south to north, the price has increased, there are some differences in prices in different regions.

PCB industry

PCB industry

2016 collapse of the traditional manufacturing industry, in 2017 the Internet bubble collapse.Enterprise transformation is a top priority to reverse the crisis.Transition, the two words are related enterprise life and death.Especially large enterprises, with annual sales of $10 enterprises, rely on is the traditional sales channels and team, talk easy transition.Die not transformation, transformation in the fear of death,Many enterprises are struggling with this is the main reason for the transformation,Timid fear the end of the "death" is the only result.Even if is dead, why don't you fight, the profit?

For the enterprise, there are two kinds of transformation:
The first kind, forced to transition, while concentrating on the problem can't solve,Reversed transmission enterprise transformation, the transformation cost is very big, also is very painful, but not the operation must be death.
The second transition, is foreseen type transformation,Is the enterprise leaders strategic insight ability strong, this kind of entrepreneur is scarce,Like that year sell PC business to lenovo, IBM is near the cheap PCS sold a high price in advance,IBM finished ahead of transformation, was very successful.But this kind of entrepreneurs in the world is rare.
Believe most of the PCB manufacturer and upstream and downstream industries are belong to the first, when the flood comes, to remember to disaster relief, the concept of no save for a rainy day.
In artificial cost, cost of raw materials under the trend of growing only, also hope to rely on bite a tooth proofed the past is not too realistic, this will only drag companies to more and more tired, tired, ending only exit the market, of course.
First of all, China has now entered the medium high income countries,Compared to income levels in the global ranking of a substantial increase in twenty years ago.More than 110 economies around the world have more than the Chinese labor cost advantage, domestic labor costs increase, have to make industrial enterprises use replace labor of science and technology innovation.
Second, the PCB industry use are traditional copper clad,And circuit board prices the main reason is that the upstream copper clad, copper foil and other raw material prices continue to rise sharply, cause the entire circuit board production cost is too high,Semi-serious also makes the downstream industry, in addition, the popularity of electronic products upgrading and increase the terminal market demand, this also support factor for the circuit board price is rising.
Avant-garde entrepreneurs recognize industry already on the market situation, vision, breaking the previous sheet, use ceramic material of the circuit board,And the ceramic chip price did not increase,In this regard, the ceramic material used in the circuit board industry has greater advantage.And also using laser rapid activation metallization technology (LAM) technology, reduce labor costs, laser cutting grinding punch master, production cycle is fast, good heat dissipation effect.Easily solve the artificial cost and material cost, and also bring more value.

Wireless charger design and analytical – circuit selection principle

Wireless charger design and analytical - circuit selection principle
Wireless charger is not the traditional charging the power cord is connected to the need to recharge on the terminal equipment of the charger,Using the latest wireless charging technology, through the use of magnetic field between the coil,Magic power transmission, inductive coupling technology will become the bridge connecting charging stations and equipment.
Most of the current charger, tablet and iPhone, for example, by means of direct contact with the metal wire, to the device with a built-in battery.Wireless charging technology has the advantage of convenience and versatility.The disadvantage is low efficiency and can only provide electricity.And Apple Dock connector not only provide electricity, as well as the audio and video files via USB sync on the device.However, wireless charging technology will bring progress to WiFi and battery technologies.For does not require data transmission equipment, this new technology will greatly reduce the number of user needs all kinds of charger.In addition, through the adoption of wireless charging technology, public mobile charging stations will likely become a reality.
Wireless charger principle and structure

Figure 1 wireless charger principle and structure
Wireless charging system mainly adopts electromagnetic induction principle, to realize the energy transfer through the coil energy coupling.As shown in figure 1, the system will work when the input ac mains by full bridge rectifier circuit into direct current, or directly with 24 v direct current for power supply system.After H H power management module of the output dc by 2 m active crystals into high frequency inverter ac supply primary winding.Through 2 H H inductor coil coupling energy, electricity flows through the secondary coil output to accept change to dc conversion circuit for the battery.
The power management module

Figure 2 power supply circuit

Emission circuit module

Figure 3 emission circuit module

As shown in figure 3, the main vibration active crystal up 2 MHZ used for oscillator circuit.Active crystals square-wave output, a second-order low-pass filter filter HHG, get stable sine wave output,The triode 13003 and its peripheral circuit composed of c class after the amplifier circuit output to coil with parallel resonant circuit of capacitance radiation. Provide energy for receiving part.
Receiving circuit module and charging circuit

Figure 4 receiving circuit
Measured with parallel resonant circuit of capacitance of tubular coupling coil wire diameter for o. 5 mm, 7 cm diameter, inductance of 47 uh, carrier frequency of 2 MHZ.According to the parallel resonant formula to match the capacitance C is about 140 pf.Thus. Launch part adopts 2 MHZ active crystals produce energy carrier frequency and resonant frequency is close to.

Figure 5 charging circuit

Wireless charger basic function is through the coil will be H electricity H in H H wireless transmission to the battery.Simply put battery and receiving device on the charging platform can be recharged.Experiments show. Although the system also can't charging in invisible. But have more than one school can do to charge platform charging at the same time, placed in the same connection problems.

Wireless transmission can charger circuit analysis – circuit selection

Wireless transmission can charger circuit analysis - circuit selection
Wireless charging is the result of radio transmission technology, low power wireless charging electromagnetic induction type, is often used to power wireless charging resonant is often used by power supply equipment (charger) to transfer energy to the utilization device, the device using the received energy of the battery, and at the same time for its own operation.
Because of the energy between the charger and power device to transmit field, without wires, between so charger and electric device can do no conductive contact the leakage.
Introduced in this paper is a simple and practical scheme of wireless transmission to the charger, it is through the coil to transmit power wireless to the bulb (battery).The wireless transmission can charger by two major part is energy sending unit and receiver unit, can be within 5 cm for rechargeable bulb (battery).
The power supply circuit

Using the 24 v and 5 v power supply to supply power field effect tube namely NE555 respectively by use of transformer substation using 7812 and 7912 the voltage source module to produce 24 v points and then by the power supply voltage to produce 7805 5 v battery.And it is important to note that two power supply.
Signal circuit

Applied by NE555 oscillation frequency is about 500 KHZ signal generator, excitation signal for power amplifier circuit.Adjust the rheostat size of 555 May be changes in a certain range of the output pulse frequency and duty ratio, and get the required frequency adjustment.
Receiver charging control circuit design

Electricity after receiving coil, high frequency ac voltage through IN4007 full-wave rectifier rectifier tube, 2200 uf capacitor filter, and then woke up with 3.3 V zener diode voltage, the output direct current for the bulb (battery) to provide a stable working voltage.
Power amplifier drive circuit
By LC resonance power amplifier and parallel resonant circuit switch tube IRF640 composition.Front-end oscillation circuit of power amplifier drive circuit is mainly used for amplification of vibration signals, thus send the higher oscillation signal in the junior high frequency power circuit.
LC resonance circuit design
Rf output energy sending unit adopts the transmitter coil (inductance and capacitance) and constitute a resonance circuit.Gain more voltage, in order to improve the energy receiving unit is able to work at greater distances, energy receiving unit adopts parallel resonant circuit.
When power amplifier circuit of frequency selective resonant frequency and the excitation signal frequency at the same time, the power amplifier in resonance, the maximum voltage and current in coil, resulting in a maximum of alternating electromagnetic field.When the receiver coil and the transmitter coil near the output voltage is induced in the receiving coil, when the resonance frequency of the receiver coil circuit and transmitting frequency resonate at the same time, the voltage of the maximum value.So the transmitter coil circuit and receiving coil circuit are in a state of resonance, has the best effect of energy transmission.Coil transfer energy efficiency is higher, the greater the distance between.
Receiver charging control circuit design
Electricity after receiving coil, high frequency ac voltage through IN4007 full-wave rectifier rectifier tube, 2200 uf capacitor filter, and then woke up with 3.3 V zener diode voltage, the output direct current for the bulb (battery) to provide a stable working voltage.

The wireless transmission  charger solutions and improvement need pay attention to the following points:
(1)in the transmission distance, under the condition of coil parameter is set, the sender must have the higher frequency, the transmitting coil in the resonance state, etc. Make transfer efficiency increases.
(2)methods for the improvement of distance is to improve the transmission circuit of voltage.
(3)the design adopts IN4007 rectifier rectifier tube, pipe pressure drop an average of 0.8 V.Conduction loss is big, not suitable for use in the receiving circuit.And if the schottky diode can greatly reduce the loss of the pipe, electrical energy utilization is higher.
(4) copper wire diameter, coil diameter size, number of turns and winding method not only determines the coil inductance value, also affects the efficiency of its transport.

Signaling speed limit and circuit board microminiaturization request

Along with the computer run speed rise, between the central processor and the peripheral component information transmission and the signal deposit and withdrawal needs in extremely short instantaneous to complete.For example within nanosecond or shorter time (10-9 second ~10-10 second).
These the fast transmission signal are carries on between the chip in the printed circuit panel metallic conductor.It is well known, signal dissemination demand time.The detention influence speeds up along with the frequency enlarges.Signal delay in electric circuit panel biggest, is small on multi-chip module (MCM), is smallest on the chip.Therefore the MCM technology is suitable for the high performance system.Is the 90's hot spots.In here us wants to point out the MCM technology arrived this new century to wither largely, its reason was the production cost too is expensive.

The present 3D chip superimposition technology looked like substitutes the MCM technology.In order to reduce the signal delay, may the component which corresponds mutually draw close to the placement.
Reduces between as far as possible them the signal path of propagation.This proposed to the electric circuit board the microminiaturized request, reduces the foundation plate 'OR' circuit board material the dielectric constant to increase the signal running rate.This proposed to the electric circuit board the microminiaturized request, reduces the foundation plate 'OR' circuit board material the dielectric constant to increase the signal running rate.In order to satisfy the component which mutually will correspond to draw close to the placement the request, will have to make the high density interconnection foundation plate/electric circuit board.
Most components will interlock in the smallest space.Is uses the micro channel interconnection technique in the technical stratification plane and unifies the precise narrow spacing metal fine lace technology.

The thing often has the duality, besides the manufacture difficulty, the thin metal wire does not favor the transmission high speed signal.Leading
The wire is thinner, the high speed signal passes ability is lower.Therefore in design high speed movement system time must the concurrently density and the speed request.When to high speed signal transmission line, must use certain section according to the signal velocity request the heavy line.And maintains the enough line spacing to prevent the disturbance between the signal.