Pinsheng Electronics Co.,Ltd
What is an aluminum board
A PCB is a printedcircuit board, or printedcircuit board.
Aluminum Board is a kind of PCB:
Aluminum board is a kind of metal base copper plate with good heat dissipation function. Generally, single panel is composed of three layers, namely circuit layer (copper foil), insulation layer and metal base layer.
For high-end use are also designed as double panel, and the structure is circuit layer, insulation layer, aluminum base, insulation layer, circuit layer.
Very few applications are multi-layered, which can be made by ordinary multi-layered board with insulating layer and aluminum base.
One - sided aluminum substrate: it is only one layer of conductive graphics layer with insulating material aluminum (substrate).
Double-sided aluminum substrate: there are two conductive graphic layers which are superimposed on the insulating material and aluminum substrate.
Multilayer printed aluminium base circuit board: printed circuit board made of three or more layers of conductive graphics and alternating lamination of insulating material and aluminum base plate.
Divided by surface treatment:
Electric gold plate
Molten tin plate
Heavy tin plate
Heavy silver plate
Electric silver plate
Heavy palladium plate
Working principle of aluminum substrate
The surface of the power device is mounted on the circuit layer, and the heat generated during the device operation is quickly transferred to the metal base through the insulation layer, and then the heat is transferred from the metal base to realize the heat dissipation of the device (see figure 2).
Compared with the traditional FR-4 ratio, aluminum substrate can reduce the thermal resistance to the minimum, so that aluminum substrate has excellent thermal conductivity.
Compared with the thick - film ceramic circuit, its mechanical properties are excellent.
In addition, aluminum substrate has the following unique advantages:
Comply with RoHs requirements;
More suitable for SMT process;
The thermal diffusion is treated effectively in the circuit design scheme, so as to reduce the operating temperature of the module, extend the service life, and improve the power density and reliability.
Reduce the assembly of radiators and other hardware (including thermal interface materials), reduce product volume, and reduce hardware and assembly costs;
Optimize the combination of power circuit and control circuit;
Replace fragile ceramic substrate for better mechanical durability.
The composition of aluminum substrate
1. The circuit layer
The circuit layer (usually electrolytic copper foil) is etched to form printed circuit, which is used to realize the device assembly and connection.
Using the same thickness, the same line width, the aluminum substrate is capable of carrying higher currents than conventional fr-4.
2. The insulation layer
Insulating layer is the most core technology of aluminum substrate, which mainly functions as adhesion, insulation and heat conduction.
The insulating layer of aluminum substrate is the largest thermal barrier in power module structure.
The better the insulation layer's thermal conductivity is, the more conducive it is to the heat diffusion generated during the device's operation, and the more favorable it is to reduce the device's operating temperature, so as to improve the power load of the module, reduce the volume, prolong the life and improve the power output.
3. Metal base
The type of metal used in insulating metal substrate depends on the comprehensive consideration of the thermal expansion coefficient, thermal conductivity, strength, hardness, weight, surface condition and cost of the metal substrate.
Properties of aluminum substrate
I. heat dissipation
At present, many double panel, multilayer board density is high, power is big, quantity of heat sends out is difficult.
Conventional PCB substrates, such as FR4 and CEM3, are poor conductors of heat.
The aluminum substrate can solve the heat dissipation problem, which is caused by the local heating of electronic devices.
2. Thermal expansion
Heat expansion and contraction are the common nature of matter.
Aluminum base PCB can solve the heat dissipation problem effectively, so that the problem of heat expansion and cold shrinkage of components and components on the PCB can be alleviated, and the durability and reliability of the whole machine and electronic equipment can be improved.
Especially solve the problem of hot expansion and cold shrinkage of SMT (surface mount technology).
Aluminum - based PCB is obviously much more stable in size than insulating PCB.
Aluminum base PCB, aluminum sandwich board, from 30 ℃ heating to 140 ~ 150 ℃, size of 2.5 ~ 3.0%.
4. Other reasons
Aluminum substrate board, with shielding function;
Replacing brittle ceramic substrates;
Safe use of surface mounting technology;
Reducing the real effective area of the PCB;
It replaces radiators and other components to improve heat resistance and physical properties.
Reduce production costs and labor.
V. technological process of aluminum substrate manufacturing
1. Material opening process
Incoming, open, baking
Material: the raw material made of thermal conductive material or semi-solidified sheet and pressed on aluminum foil to make aluminum PCB.
Opening: opening is the process of cutting a piece of bulk into small pieces by machine according to different requirements.
The edge of the plate after the material is sharp, easy to scratch the hand, and at the same time make the board between the scratch, so after the material open the edge grinding machine.
1. Purpose of baking board:
To eliminate the internal stress of the plate during manufacture.
Improve dimensional stability of materials.
Remove the moisture absorbed by the sheet during storage.
Increase material reliability.
2. Baking conditions:
150 ℃ for board 4 hours, laminated thickness usually 50 mile
M a bundle of
2. Purpose of feeding
Shearing the incoming material of large size into the required size for production
3. Matters needing attention for opening materials
Check the size of the first piece
Pay attention to aluminum and copper scratches
Pay attention to plate edge stratification and sweep edge
2) dry/wet film imaging
Wet film (also known as photosensitive line oil) and photosensitive dry film are photosensitive materials. When exposed to ultraviolet light, they polymerize to form a relatively stable image.
1. Dry/wet film imaging process
Grinding plate - film - exposure - development
2. Purpose of dry/wet film imaging
The part needed for making the circuit is presented on the sheet
3. Precautions for dry/wet film imaging
Check whether the line is open after developing
Is there a deviation of the developing pair to prevent the dry film from breaking
Pay attention to poor wiring caused by friction on the board
Air residues must not be present during exposure to prevent poor exposure
After the photo exposure, the film should be stationary for more than 15 minutes before developing
The effect of exposure is that the uv light of the exposure machine makes part of the image on the film through the negative, thus transferring the image to the copper plate.
Function of development:
Is the unexposed part of the dry film removed, leaving the part of light.
Principle of development:
The photosensitive material in the unexposed part did not undergo polymerization and was dissolved in weak base Na2CO3 (0.8-1.2%).
The polymer material remains on the plate to protect the underlying copper from etching solution.
1. Acid/alkaline etching process
Etching - stripping - drying - inspection plate
2. Acid/alkaline etching purpose
After the dry/wet film is imaged, the required part of the circuit is retained, and the excess part is removed
3. Matters needing attention for acid/alkaline etching
Pay attention to poor etching and excessive etching
Pay attention to the line width and the line length
The copper surface of the coating is not allowed to be oxidized and scratched
Keep dry film clean
The effect of etching:
Is the unexposed part of the copper surface etched off.
4) faded film
The film on the copper surface of the protective circuit is removed by using a relatively high concentration of NaOH (3-5%). The concentration of NaOH solution cannot be too high, otherwise it is easy to oxidize the plate surface.
5) AOI process
The principle of the machine is to use the reflection effect of copper surface to make the pattern on the plate can be scanned by AOI machine and recorded in the software, and check the defect point by comparing with the data graph data provided by the customer. Defects such as open circuit, short circuit and poor exposure can be checked by AOI machine.
The function of brown chemical sequence is to coarsen the copper surface, increase the combined area and increase the surface binding force.
Process description: the pressure plate is a semi-solidified sheet that connects the outer copper foil to the inner layer and each inner layer to the inner layer.
Process principle: with the characteristics of semi-solidified sheet, it melts at a certain temperature and becomes a liquid filled graphic space, forming an insulating layer. After further heating, the insulation layer is gradually solidified to form a stable insulating material. At the same time, each layer of each line is connected into a whole multi-layer board.
What is a semi-curing tablet (PP)?
Prepreg is an abbreviation of Prepreg.
It is a kind of sheet bond material synthesized by resin and glass fiber carrier.
Resins - usually macromolecular polymers, a hot - solid material.
The current commonly used is epoxy resin FR-4.
1. The process of drilling
Drill pin - drill - test plate
2. Purpose of drilling
Position drilling of the plate to assist the following production process and customer assembly
3. Precautions for drilling
Check the number and size of holes
Avoid scratching the sheet material
Examine the flanges of the aluminum surface, hole position deviation
Timely inspection and replacement of drill heads
The boring hole is divided into two stages, one drilling: the drilling after the material is made is the peripheral tool hole;
Second drilling: the tool hole in the unit after resistance welding
Characteristics of aluminum base plate drill nozzle
The chip discharge space of the high-order bit is large: the chip discharge resistance is small, chip discharge is smooth, the heat of drilling is small, and the drilling pollution is reduced;
Thanks to nanotechnology and advanced grinding technology, the cutting edge of the drill bit is sharper than before, reducing cutting force, cutting rate and improving hole wall quality.
Design of tools based on customer application: the variety of drills is rich and can meet different application requirements.
All the parameters of the drill bit, such as drill core thickness and drill core taper, are carefully designed and effective.
Rigid symmetry of the machined edge: good for efficient cutting and avoid drift of borehole.
9) copper plate plating
A conductive metal layer is deposited in the hole of the plate after drilling by chemical method, and the metal layer is thickened by whole plate electroplating method, so as to achieve the purpose of metallization in the hole and make the circuit pass through by this method
Grinding plate - removing glue slag - settling copper - plate electroplating - down procedure
Electroless Copper Deposition, commonly known as Copper Deposition, is a self-catalyzed chemical oxidation and reduction reaction. In the process of Electroless Copper plating, Cu2+ ions are electronically reduced to Copper metal. When the reducing agent releases electrons, the reducing agent itself is oxidized.
Electroless copper plating is used to metallize holes in the manufacture of printing plates to complete the wire connection between double panel and multi-panel layers.
Screen printing resistance welding and characters
1. Screen printing resistance welding and character flow
Screen - prebake - exposure - development - characters
2. Purpose of screen printing resistance welding and characters
Solder - free: protect the line that does not require soldering, prevent the solder from entering and causing a short circuit
The character: serves as a marker
3. Matters needing attention for screen printing resistance welding and characters
To check if there is any garbage or foreign matter on the board
Examine the cleanliness of the board
The printing should be pre-baked for more than 30 minutes to avoid air bubbles
Note the thickness and evenness of the screen printing
The pre - bake after the plate to fully cool, to avoid film or damage ink surface gloss
To develop the ink face down
1. Procedures of v-cut and gongs
V-cut -- gongs -- tear protective film -- strip the front
2. Purpose of v-cut gongs
Peripheral v-cut: connect the single PCS line with the sheet cutting of the whole PNL to facilitate packaging and taking out
Causeway board: remove any excess from the circuit board
3. Precautions for v-cut and gongs
The size of V should be paid attention to in the process of finishing v-cut
When the gongs were in causeway, the burr was caused, the gongs were deflected, and the gongs were inspected and replaced in time
To avoid surface scratches at the end
7) testing, OSP
1. Testing, OSP process
Line testing - voltage resistance testing - OSP
2. Testing, purpose of OSP
Circuit test: check whether the completed circuit is working normally
Voltage withstand test: check whether the completed line can withstand the specified voltage environment
OSP: make the wire better for soldering
3, testing, OSP considerations
How to distinguish between qualified and unqualified products after checking
So when you're done with the OSP, the placement
Protect the wiring from damage
8) FQC, FQA, packaging and shipment
FQC - FQA - packaging - shipping
2, the purpose,
Qc will check and confirm the product
Qc spot check and verify
Nail pack and ship to customer as required
Use of aluminum substrate for PCB
1. Audio equipment: input/output amplifier, balance amplifier, audio amplifier, preamplifier, power amplifier, etc.
2. Power equipment: switching regulator ` DC/AC converter ` SW regulator, etc.
3. Communication electronic equipment: high frequency increase ` filtering electrical ` transmitting circuit.
4. Office automation equipment: motor driver, etc.
5. Car: electronic regulator ` igniter ` power controller, etc.
6. Computer: CPU board ` ` floppy drive power supply device, etc.
7. Power module: inverter ` solid relay ` rectifier bridge, etc.
8. Lighting decoration: with the promotion of energy-saving lamps, aluminum substrate applied in LED lamps has also started to be widely used.
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