The hottest plasma processing PCB processing

2022-08-19
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Plasma treatment printed circuit board processing

[preface]

gas plasma treatment is a convenient, efficient and high-quality method for PCB decontamination and back etching. Plasma treatment is particularly suitable for FR4, polyimide and polytetrafluoroethylene (PTFE) materials because of their poor chemical activity. Plasma treatment has more activation activity

through high-frequency generator (typical 40KHz), use the energy of electric field to separate the processing gas and establish plasma technology under vacuum conditions. These excited unstable separated gas substances will modify and bombard the surface. Treatment processes such as UV fine cleaning, activation, consumption and crosslinking, and plasma polymerization are the functions of plasma surface treatment

[advantages of plasma processing technology]

1. The processing technology can be controlled. 2. Environmental protection technology

3. Low cost processing technology. 4. Cost of waste without treatment

5. Drying treatment

[principle of plasma processing workpiece]

plasma is the product of glittering and translucent light from ultraviolet ray. It is the fourth state of matter after solid, liquid and gas. Plasma has ions, free electrons, photons, neutrons, atoms, molecules and other excited electronic states. Each component has the ability to treat the surface. Using the high voltage to the ground, 40KHz and 13.58mhz high-frequency generators make the gas become plasma. 2.54ghz microwave system is the third kind of equipment to establish plasma state

the above three high-frequency generators with different frequencies have slightly different adaptability in application. The activated atoms, molecules, ions and free electron substances are highly concentrated, which can interact with the solid surface in the plasma state, causing the chemical and physical modification of the material surface

plasma surface treatment has the following functions: cleaning; Activation; Ablation; Crosslinking

[cleaning]

cleaning is to remove weak bonds and use typical ch based organic dirt. The main feature is that it only works on the surface without eroding the internal function, so as to get an ultra-high clean surface and prepare for the next process

[activation]

activation is the formation of carbonyl carboxyl carboxyl hydroxyl hydroxyl groups on the surface. This group has a stable function and has a positive effect on bonding hydrophilicity to replace weak bonds. It mainly increases the surface energy. For polymers, low surface energy leads to poor adhesion

[crosslinking]

crosslinking is carried out in inert gas. The bond is broken and recombined to form a double bond or a triple bond, or a bond in which a free radical is combined with another bond

[ablation]

ablation is to remove polymer chains and weak bonds when bombarding the surface of structural plates used by polymers in a dry state. This is conducive to the decontamination and back etching of printed circuit boards. The above three actions are the synthesis of the cross actions of plasma surface treatment. The best effect can be obtained by selecting process parameters and gas mixing ratio reasonably and correctly

[process parameters]

in plasma treatment, the reasonable selection of the following process parameters plays an important role

gas type and mixing ratio; Power; Processing time; Studio pressure; Gas flow

[gas mixing]

oxygen is the most commonly used gas to clean and activate polymer surfaces and other surfaces. Inert gases such as ammonia are crosslinking. Other gases such as CF4 are more reactive. The optimal process can be obtained by mixing different gases

[gas flow]

according to the volume of the working room, the vacuum pumping system and the working pressure determine the size of the gas flow, especially the working pressure and the gas flow are more closely related

[working pressure]

plasma treatment is stable within a certain working pressure range. Too low or too high working pressure leads to unstable plasma treatment. If the high-frequency generator cannot meet the system requirements, the plasma treatment will be unstable

for RF system, working pressure between Torr is the most suitable. Low working pressure leads to long life of activated substances. Higher working pressure can get a higher degree of gas utilization. Therefore, optimization is necessary

[processing time]

a longer processing time generally allows deeper decontamination and etching of printed circuit boards. In some cases, the repair time is too long, resulting in excessive treatment or heat damage

[power]

high power can shorten the processing time. High power makes the activated substance more active. Power plays an important role in heat generation. It's not that the higher the power, the better

[precautions]

high power and long processing time will affect the temperature in the studio. Too high working pressure also reduces the efficiency of plasma treatment

[application]

select process parameters according to different treatment materials. Different types of plasma processing equipment, such as CD 600pc and cd-1000pc, have different working volumes; The process parameters are different. Provide corresponding process parameters randomly. Special material processing requires some fine-tuning of process parameters

[processing of FR4 printed circuit board]

in order to decontaminate and etch the back of the printed circuit board, isotropic FR4 printed circuit board. The mixture of CF4 and oxygen can be used for etching.

1) heating process is carried out through the following four steps: 20 minutes, using oxygen, power 3000W, heating to 70 ℃

<5. If the control system of the tension machine is dial reading (that is, the type whose value passes through one dial degree is called dial), then the oil change is troublesome; p> 2) 20 minutes of decontamination and back engraving process, o2/cf4 (85/15 to 90/10% mixed) power 3000W

319. Host size: 1000*680*2450mm;) Cleaning/activation process 5 minutes O2 power 3000W

4) the remaining CF4 gas is excluded during the N2 feeding process

the etching gas is the mixture of CF4 and oxygen. Adding CF4 gas can improve the etching rate, but the disadvantage is that some parts of the plasma processing equipment (such as O-shaped sealing ring) will be damaged, so the ratio of gas mixing should be controlled at%

temperature is a very important parameter, so the heating process should be set specifically in the ion treatment. The plasma equipment can measure the temperature and automatically switch to the next process when the temperature reaches. The setting of temperature is controlled by computer. High temperature leads to high etching rate, usually 60 ℃ -80 ℃. Higher temperature will damage printed circuit boards, especially thin printed circuit boards

it is necessary to clean the activation process in order to intensify the surface of the printed circuit board, because the surface water repellency can be obtained by treating with CF4 gas

[treatment of polyimide Kapton printed circuit board]

flexible printed circuit board made of polyimide can be treated by plasma whether there is adhesive or not. The same process parameters can be applied to DuPont's Kapton materials

[through hole treatment of Teflon printed circuit board.]

polytetrafluoroethylene PTFE is an inert material. Its processing purpose is to activate the surface of polytetrafluoroethylene, and its activation level can reach dyne surface tension. Due to the limited service life, it is required to immediately carry out metal treatment on the material surface within the same day

the processing technology is N-H or He-O2. The chemical action begins with a very active NH2 gas. The disadvantages of ammonia are odor and the need for special MFC controller. For cd-1000pcb plasma processing equipment, the parameters used are as follows

1. heat with N2 or inert gas (without O2) with a power of 2500W for 10 minutes until the temperature is 70 ℃

2. Input o2/he (50/50% mixed gas) for 10 minutes, power 2000W

3. Input 100% he5 min power 2000W

the heating process has very strict requirements for some very thin printed circuit boards, which can be eliminated or reduced. For the machine, the gas flow can be controlled, but the process pressure must be about Torr. After treatment, the surface is active, and no other processing is required before metallization

[Conclusion]

europlasma plasma equipment can provide micro adjustment of process parameters to achieve optimal results for surface treatment of different materials. Practice has proved that high quality printed circuit boards can be obtained by plasma surface treatment of multilayer soft or hard materials

reprinted from: China Hong Kong silk screen

should be replaced to check whether the circuit board is damp or greasy

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