CN118632442B - A control method for circuit board ICD - Google Patents

Abstract

The invention discloses a control method of a circuit board ICD, which relates to a technology for improving the interconnection defect of an inner layer of the circuit board, and belongs to the field of printed circuit manufacturing, and comprises the following steps: placing the circuit board into a processing chamber of a plasma photoresist remover, and discharging air in the processing chamber; starting a plasma photoresist remover, and raising the temperature of the processing chamber to 80-100 ℃; introducing first mixed gas into the processing chamber at a flow rate of 2 SLM-3.25 SLM, wherein the first mixed gas comprises O ₂, N ₂,O₂ and N ₂, the mixing ratio of the first mixed gas to the N ₂ is 3:1-5:1, and the time for introducing the first mixed gas lasts for 30-70 minutes; introducing a second mixed gas into the processing chamber at a flow rate of 2 SLM-3.25 SLM, wherein the second mixed gas comprises O ₂、CF₄、N₂, the ratio of O ₂ is 60-90%, the ratio of CF ₄ is 5-20%, the ratio of N ₂ is 5-20%, and the time for introducing the second mixed gas lasts for 45-90 minutes; o ₂ is introduced into the processing chamber at a flow rate of 2 SLM-3.25 SLM, and the time of introducing O ₂ lasts for 10 minutes-15 minutes. The invention can effectively solve the problem of the interconnection defect of the inner layer of the circuit board and has higher glue removing efficiency.

Description

A control method for circuit board ICD

Technical Field

The invention relates to a circuit board inner layer interconnection defect improvement technology, belongs to the field of printed circuit manufacturing, and particularly relates to a circuit board ICD control method.

Background Art

In recent years, the demand for circuit boards has continued to grow, driving the rapid development of related technologies. For multi-layer circuit boards, the traditional multi-layer board lamination and via hole (through hole) degumming process is no longer effective. In addition, with the reform of PCB (printed circuit board) material technology and the refinement of appearance, as well as the use of new material boards with high Tg (glass transition temperature ≥ 170℃) and low signal loss, these boards have solved the problem of thermal expansion coefficient and have been widely used.

However, the sheet materials currently used have a high Tg resin system. These resins may contain more cross-linking points or rigid groups in the molecular structure, making the material more stable when heated, but also increasing the content of inert components. Some sheet materials also use carbon fiber or silicon fiber as reinforcement materials. These fibers may break during the drilling process and remain in the hole wall. In addition, the via holes are smaller in size on more delicate circuit boards. The above factors make the original chemical degumming process less effective. The traditional (potassium permanganate, sodium hydroxide) degumming process solution cannot completely penetrate into the small via holes, nor can it effectively clean the residual glue formed by drilling the current sheet materials, especially the inert materials cannot be cleaned. This problem is very likely to cause ICD problems (Inner Connection Defects), that is, connection separation defects caused by residual glue in the inner layer. As shown in FIG. 2 and FIG. 3 , it can be seen that after being processed by the existing processing method, there is an obvious separation between the metal material of the via hole and a layer of connecting wires in the circuit board. FIG. 4 shows that there is 2.67 μm of residual glue at the separation point, which is a relatively serious connection separation defect.

Summary of the invention

In view of the above problems, the present invention provides a control method for a circuit board ICD, which can effectively solve the problem of inner layer interconnection defects of the circuit board and has a high glue removal efficiency.

In order to achieve the purpose of the present invention, the following scheme is adopted:

A control method for a circuit board ICD comprises the following steps:

S100: placing the circuit board into a processing chamber of a plasma debonding machine, and exhausting the air in the processing chamber;

S200: Start the plasma degumming machine and increase the temperature of the processing chamber to 80℃~100℃;

S300: introducing a first mixed gas into the processing chamber at a flow rate of 2SLM to 3.25SLM, wherein the first mixed gas includes O ₂ and N ₂ , and the mixing ratio of O ₂ to N ₂ is 3:1 to 5:1, and the time for introducing the first mixed gas lasts for 30 minutes to 70 minutes;

S400: introducing a second mixed gas into the processing chamber at a flow rate of 2SLM to 3.25SLM, wherein the second mixed gas includes O ₂ , CF ₄ , and N ₂ , and the proportion of O ₂ is 60% to 90%, the proportion of CF ₄ is 5% to 20%, and the proportion of N ₂ is 5% to 20%. The time for introducing the second mixed gas lasts for 45 minutes to 90 minutes;

S500: O ₂ is introduced into the processing chamber at a flow rate of 2 SLM to 3.25 SLM, and the time for introducing O ₂ is continued for 10 minutes to 15 minutes.

Further, after S500 is completed, S600 is executed: taking out the circuit board and cooling it.

Furthermore, in S200, the temperature of the processing chamber is increased to 90°C.

Further, in S300, the flow rate of the first mixed gas introduced into the processing chamber is 3.25 SLM; in S400, the flow rate of the second mixed gas introduced into the processing chamber is 3.25 SLM; in S500, the flow rate of _O2 introduced into the processing chamber is 3.25 SLM.

Furthermore, the mixing ratio of O ₂ and N ₂ in the first mixed gas is 4:1.

Furthermore, in the second mixed gas, _O2 accounts for 80%, _CF4 accounts for 10%, and _N2 accounts for 10%.

Furthermore, the first mixed gas is introduced for 50 minutes, and the second mixed gas is introduced for 75 minutes; in S500, O ₂ is introduced for 10 minutes.

Furthermore, a plasma degumming machine with a plasma generator rated power ≥ 10000W is used for processing. In S300, the plasma generator power is set to 7000W~8500W; in S400, the plasma generator power is set to 4500W~6000W; in S500, the plasma generator power is set to 3000W~4500W.

Further, in S300, the power of the plasma generator is set to 8500W; in S400, the power of the plasma generator is set to 6000W; in S500, the power of the plasma generator is set to 4500W.

The beneficial effects of this technical solution are:

1. In the control method of ICD of the circuit board, firstly, plasma degumming can be used to achieve comprehensive degumming inside the tiny holes. Secondly, on this basis, the method has three stages of introducing gas for plasma degumming. The types and proportions of gases used in these three stages have the following effects and principles for solving the ICD problem: (1) In the first stage: _O2, as a strong oxidant, can react with the residual glue in the inner layer of the via hole during the plasma degumming process to accelerate its decomposition and removal. _N2 does not directly participate in the chemical reaction, but can dilute oxygen and other active components in the plasma, which helps to control the reaction rate and maintain the stability of the plasma, protect the processing chamber and equipment from direct erosion by high temperature and active gases, and extend the service life of the equipment. Controlling the mixing ratio of _O2 and _N2 can maintain the smooth progress of the reaction while increasing the degumming rate. When _O2 and _N2 are mixed in a ratio of 3:1 to 5:1, it is sufficient to achieve a higher degumming rate; (2) In the second stage: _O2 and _N2 continue to play a role, introducing a small amount of _CF4 , decomposed in the plasma to produce fluorine free radicals, fluorine free radicals have extremely strong reactivity and can remove those pollutants that are difficult to be removed by oxygen alone in the first stage, such as certain compounds containing silicon or carbon, and inert additives or fillers. These substances are not sensitive to oxidation reactions and are therefore difficult to completely remove by O _2. In addition, CF ₄ is introduced in the second stage to avoid the premature introduction of CF _4, which causes strong fluorination and oxidation to occur simultaneously, and causes fluorine free radicals to react with organic matter that has not been completely oxidized, resulting in poor removal of residual glue. In addition, although the current circuit board materials increase the inert components in the via holes, some boards also use carbon fiber or silicon fiber as reinforcement materials, but the proportion of these materials is not large, and excessive use of CF ₄ will produce some toxic and harmful fluorides, as well as corrosive substances, which will damage the processing chamber and equipment. Therefore, when the gas ratios are carried out in the second stage, O ₂ is still the main one. Taking these factors into consideration, O ₂ accounts for 60%~90%, CF ₄ accounts for 5%~20%, and N ₂ A proportion of 5% to 20% can ensure a good degumming effect and improve stability; (3) In the third stage: pure oxygen can be used to remove the carbonized byproducts of the plasma reaction on the resin in the previous stage.

2. After the temperature of the processing chamber is raised to 80℃~100℃, the gas is plasmatized by a plasma generator to maintain the temperature. A longer processing time is adopted in the first stage to make the surface temperature of the sheet material evenly distributed, avoid local overheating or insufficient temperature, and facilitate oxidation reaction. In the second stage, _CF4 is introduced. It takes a certain amount of time for the gas mixture of different components and proportions to reach a stable state in the reaction chamber. Therefore, the reaction time required is longer, which is convenient for deep degumming. The third stage is the finishing stage, and the by-products are removed in a shorter time.

3. The control method of the circuit board ICD is used to treat the residual glue in the via holes of the multi-layer board. The degumming rate is high, and the glue residue and drilling contamination in the hole can be effectively removed. When degumming multiple circuit boards at the same time, the uniformity of the degumming rate is good, which can solve the problem of inner layer interconnection defects of the circuit board, and will not cause unnecessary damage to the hole wall after treatment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the brief steps of the circuit board ICD control method.

FIG. 2 shows a first schematic diagram of the background technology.

FIG. 3 shows a second schematic diagram of the background technology.

FIG. 4 shows a third schematic diagram of the background technology.

FIG. 5 shows a table of test results of the circuit board degumming rate.

FIG. 6 shows a table showing the test results of negative etching of residual adhesive in a hole by plasma gas.

DETAILED DESCRIPTION

In order to make the purpose, technical solutions and advantages of the present application clearer, the implementation methods of the present application are described in detail below, but the embodiments described in this application are only part of the embodiments of the present application, rather than all the embodiments.

Based on the brief steps of the circuit board ICD control method shown in FIG1 , the method is implemented in detail according to the following steps:

S100: placing the circuit board into a processing chamber of a plasma debonding machine, and exhausting the air in the processing chamber;

S200: starting the plasma degumming machine, raising the temperature of the processing chamber to 80° C. to 100° C., preferably 90° C. Specifically, this step realizes heating through an electric heating plate inside the plasma degumming machine;

S300: introducing a first mixed gas into the processing chamber at a flow rate of 2SLM to 3.25SLM, preferably 3.25SLM, the first mixed gas comprising O ₂ and N ₂ , the mixing ratio of O ₂ to N ₂ being 3:1 to 5:1, preferably 4:1, and the time for introducing the first mixed gas lasts for 30 minutes to 70 minutes, preferably 50 minutes;

S400: introducing a second mixed gas into the processing chamber at a flow rate of 2SLM to 3.25SLM, preferably 3.25SLM, the second mixed gas comprising O ₂ , CF ₄ , and N ₂ , and O ₂ accounts for 60% to 90%, CF ₄ accounts for 5% to 20%, and N ₂ accounts for 5% to 20%, preferably O ₂ accounts for 80%, CF ₄ accounts for 10%, and N ₂ accounts for 10%. The time for introducing the second mixed gas lasts for 45 minutes to 90 minutes, preferably 75 minutes;

S500: introducing O ₂ into the processing chamber at a flow rate of 2SLM to 3.25SLM, preferably 3.25SLM, and the time for introducing O ₂ lasts for 10 minutes to 15 minutes, preferably 10 minutes;

S600: Take out the circuit board and cool it to room temperature, specifically, it needs to be cooled to below 30° C. at least.

The SLM mentioned above is the abbreviation of Standard Liter per Minute, which is used to indicate the volume of fluid flowing through a certain place per unit time under standard conditions (0°C, 1 standard atmospheric pressure).

Preferably, a plasma degumming machine with a plasma generator rated power ≥ 10000W is used for processing, and: in S300, the plasma generator power is set to 7000W~8500W, preferably 8500W. High power can produce high-density plasma and strong physical bombardment effect, which can more effectively bombard the residual glue in the hole wall, causing it to begin to decompose and loosen; in S400, the plasma generator power is set to 4500W~6000W, preferably 6000W. Medium power can maintain a certain plasma density and active particle energy, and avoid unnecessary damage to the circuit board caused by excessive energy; in S500, the plasma generator power is set to 3000W~4500W, preferably 4500W. This stage is mainly to remove carbonization by-products, so low power is maintained to make the plasma density and active particle energy moderate.

In order to illustrate the ICD control effect that can be achieved by the above method, the following tests were performed:

1. Glue removal rate test: In Figure 5, "Circuit board number on carrier" indicates a specified circuit board on a circuit board carrier in the processing chamber. There are 9 circuit boards placed on each circuit board carrier. "Circuit board carrier position in the processing chamber" indicates the circuit board carriers at the left, middle and right positions in the processing chamber. Since the plasma in the processing chamber is more likely to bombard the circuit board that is perpendicular to the airflow direction, the glue removal process is sometimes not uniform. Therefore, it is necessary to test the glue removal rate of the circuit boards at various positions.

From the degumming rates of 27 circuit boards, it can be seen that the minimum value is 169.70 mg/cm ² , the maximum value is 279.40 mg/cm ² , and the average value is 212.28 mg/cm ² , indicating that the degumming rate level is relatively high.

For the uniformity of the degumming rate, if the formula [1-(maximum value-minimum value)/(2*average value)]*100% is used for calculation, we can get [1-(279.40-169.70)/(2*212.28)]*100%=74.16%, which is a high uniformity.

2. Negative etching test of residual glue in the hole by plasma gas: First of all, "negative etching" means that in the plasma treatment process, in addition to removing the residual glue in the hole, it may also cause unnecessary erosion or damage to the hole wall or substrate material to a certain extent.

In this test, the metal connection positions and negative etch distances of the 27 circuit boards in the previous debonding rate test were observed. First, there was no disconnection at the metal connection positions of all the circuit boards, and the negative etch distances were: (1) The negative etch distances of the first to ninth circuit boards on the left circuit board carrier were: 0.36mil, 0.33mil, 0.36mil, 0.33mil, 0.36mil, 0.40mil, 0.36mil, 0.43mil, 0.36mil; (2) The negative etch distances of the first to ninth circuit boards on the middle circuit board carrier were: 0.36mil, 0.33mil, 0.36mil, 0.33mil, 0.36mil, 0.40 ... The negative etching distances of the first to ninth circuit boards are: 0.40mil, 0.33mil, 0.36mil, 0.33mil, 0.47mil, 0.36mil, 0.36mil, 0.43mil, 0.36mil; (3) The negative etching distances of the first to ninth circuit boards on the right circuit board carrier are: 0.40mil, 0.40mil, 0.33mil, 0.43mil, 0.36mil, 0.40mil, 0.36mil, 0.40mil, 0.33mil. Figure 6 is a negative etching test summary table, in which the first row and columns represent the circuit board carrier position, actual negative etching distance, required negative etching distance, and test results, respectively. The distance unit is mil, which is commonly used in the circuit board field and represents one thousandth of an inch. 1mil=0.0254 mm.

It can be seen from the negative etching test results that all the test circuit boards have solved the ICD problem and achieved normal internal connection. The negative etching distance range of the circuit boards on the left and right is controlled at 0.33mil~0.43mil, and the negative etching distance of the circuit board in the middle can reach 0.47mil. However, all negative etching distances are between 0.1mil~0.6mil required by the process. Therefore, it can be seen from the last column that all meet the process requirements.

The above are only some of the embodiments listed in this application and are not intended to limit this application.

Claims (1)

1. The control method of the ICD is characterized by comprising the following steps:

S100: placing the circuit board into a treatment chamber of a plasma photoresist remover with rated power of a plasma generator more than or equal to 10000W, and discharging air in the treatment chamber;

s200: starting a plasma photoresist remover, and raising the temperature of the processing chamber to 90 ℃;

S300: introducing a first mixed gas into the processing chamber at a flow rate of 3.25SLM, wherein the mixing ratio of the first mixed gas comprising O ₂ and N ₂,O₂ to N ₂ is 4:1, the time for introducing the first mixed gas lasts for 50 minutes, and the power of the plasma generator is set to 8500W;

S400: introducing a second mixed gas into the processing chamber at a flow rate of 3.25SLM, wherein the second mixed gas comprises O ₂、CF₄、N₂, the ratio of O ₂ is 80%, the ratio of CF ₄ is 10%, the ratio of N ₂ is 10%, the time for introducing the second mixed gas lasts for 75 minutes, and the power of the plasma generator is set to 6000W;

S500: introducing O ₂ into the processing chamber at a flow rate of 3.25SLM, wherein the time of introducing O ₂ lasts for 10 minutes, and the power of the plasma generator is set to 4500W;

s600: the circuit board is removed and allowed to cool.