A rework method for poor dry film on PCB

Abstract

The present invention discloses a rework method for a PCB board with poor dry film, comprising the following steps: S1: exposing the entire PCB board to be reworked in a film-free tool environment; S2: stripping the dry film, wherein the stripping and stripping the dry film sequentially comprises: alkali solution spray cleaning, new solution spray cleaning, acid solution spray cleaning, water washing and drying. The present invention provides a rework method for a PCB board with poor dry film, which can effectively avoid the problem of dry film residual glue entering the hole during the backwashing process, thereby ensuring the rework effect of the PCB board.

Description

Technical Field

[0001] The invention relates to the field of PCB film stripping, and in particular to a reworking method for a PCB with a poor dry film. Background Art

[0002] PCB, or printed circuit board, is a carrier for electrical connection of electronic components and is made by electronic printing. Dry film, in coating, is relative to wet film. Dry film is a polymer compound that can produce a polymerization reaction to form a stable substance attached to the board surface after being irradiated by ultraviolet rays, thereby achieving the function of blocking electroplating and etching.

[0003] Graphic transfer is an important process in the production of printed circuit boards. It transfers the designed circuit graphics to the circuit board to form an anti-etching or anti-plating mask image, and then forms a copper surface conductive pattern through the subsequent etching process. The production process of graphic transfer is: pre-treatment → film pasting → exposure → development. In each process step, defective products may be produced, such as wrinkling of the film, poor exposure, etc. In order to reduce scrap, defective boards are generally reworked by washing the dry film and re-making the graphic transfer method, but poor rework methods may cause quality defects such as dry film residual glue entering the hole, causing the PCB board to lose electrical performance; the rewashing of boards with a high aspect ratio is more likely to cause dry film residual glue to enter the hole. Summary of the invention

[0004] The present invention aims to solve one of the problems in the related art to at least a certain extent. To this end, the purpose of the present invention is to provide a rework method for a PCB board with poor dry film, which can effectively avoid the problem of dry film residual glue entering the hole during the backwashing process and ensure the rework effect of the PCB board.

[0005] In order to achieve the above-mentioned purpose, the present application adopts the following technical solution: A rework method for a poor dry film on a PCB board, comprising the following steps:

[0006] S1: The PCB to be reworked is fully exposed in a film-free tool environment;

[0007] S2: stripping and washing the dry film, which includes: alkali solution spraying washing, new solution spraying washing, acid solution spraying washing, water washing and drying.

[0008] Furthermore, the alkali solution used for alkali spraying is a sodium hydroxide solution, and the concentration of the sodium hydroxide solution is 2-4wt%.

[0009] Furthermore, the temperature of the alkali solution during spraying is less than 50°C, the production line running speed is 3-4m / min, and the spraying pressure is 2.5±1kg / cm 2 .

[0010] Furthermore, the new liquid used for spray cleaning includes the following weight components: 5-10 parts of sodium lauryl polyether sulfate, 10-15 parts of triethanolamine and 75-80 parts of water; the spray pressure of the new liquid for spray cleaning is 1.5±0.5kg / cm 2 .

[0011] Furthermore, the acid solution used for the acid spray cleaning is a 3.0±2wt% sulfuric acid solution, and the spray pressure is 1.5±0.5kg / cm 2 .

[0012] Further, the stripping and drying of the film is repeated twice, and each stripping and drying of the film comprises:

[0013] S21: alkali solution spray cleaning;

[0014] S22: new liquid spray cleaning;

[0015] S23: flushing sewage;

[0016] S24: first overflow water washing;

[0017] S25: Acid spray cleaning;

[0018] S26: second overflow water washing;

[0019] S27: high pressure water washing;

[0020] S28: third overflow water washing;

[0021] S29: Drying.

[0022] Furthermore, the parameters of the first overflow water washing, the second overflow water washing and the third overflow water washing are the same, and the spray pressure is 1.5±0.5kg / cm 2 , the overflow water flow rate is 6±2L / min.

[0023] Furthermore, the spray pressure of the high pressure water washing is 12±3 kg / cm 2 .

[0024] Furthermore, the drying temperature is 90±5° C. and the air knife pressure is ≥5 kpa.

[0025] Furthermore, in step S23, the sewage is flushed using overflow water, and the overflow water flow rate is 4±2 L / min.

[0026] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art: the present application first performs full-board exposure in a film-free tool environment for the PCB board to be reworked, so that the entire board surface is exposed and a cross-linking reaction occurs. The dry film after exposure is sequentially subjected to alkaline solution spray cleaning, new solution spray cleaning, acid solution spray cleaning and water washing processes to ensure that the dry film can be cleaned after exposure and no large pieces of dry film scraps are generated, thereby avoiding large pieces of dry film scraps adhering to the hole and affecting the quality of the hole wall in the prior art. The rework method of the present application can ensure that the hole wall after rework is not affected by the dry film, ensure that the quality of the hole wall in the PCB board after rework is not affected, and ensure the rework effect of the PCB board. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0029] In the attached figure:

[0030] Figure 1 This is a flow chart of the rework method for this application. DETAILED DESCRIPTION

[0031] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific embodiments of the present invention are now described in detail with reference to the accompanying drawings. In the following description, it should be understood that the directions or positional relationships indicated by "front", "back", "up", "down", "left", "right", "longitudinal", "horizontal", "vertical", "horizontal", "top", "bottom", "inside", "outside", "head", "tail", etc. are based on the directions or positional relationships shown in the accompanying drawings, are constructed and operated in a specific direction, and are only for the convenience of describing the present technical solution, rather than indicating that the mechanism or element referred to must have a specific direction, and therefore cannot be understood as a limitation to the present invention.

[0032] It should also be noted that, unless otherwise clearly specified and limited, the terms such as "installed", "connected", "connected", "fixed", "set" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. When an element is referred to as being "on" or "under" another element, the element can be "directly" or "indirectly" located on the other element, or there may be one or more intermediate elements. The terms "first", "second", "third", etc. are only for the convenience of describing the present technical solution, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second", "third", etc. can explicitly or implicitly include one or more of the features. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0033] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, mechanisms, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

[0034] Please see attached Figure 1 The present application provides a rework method for a PCB board with a poor dry film, comprising the following steps:

[0035] S1: The PCB to be reworked is fully exposed in a film-free tool environment;

[0036] S2: stripping and washing the dry film, which includes: alkali solution spray cleaning, new solution spray cleaning, acid solution spray cleaning, water washing and drying.

[0037] The present application first performs full-board exposure in a film-free tool environment for the PCB board to be reworked, so that the entire board surface is exposed and a cross-linking reaction occurs. The dry film after exposure is sequentially subjected to an alkali solution spray cleaning, a new solution spray cleaning, an acid solution spray cleaning and a water washing process to ensure that the dry film can be cleaned after exposure and that no large pieces of dry film scraps are generated, thereby avoiding the large pieces of dry film scraps adhering to the hole and affecting the hole wall quality in the prior art. The rework method of the present application can ensure that the hole wall after rework is not affected by the dry film, ensure that the hole wall quality in the PCB board after rework is not affected, and ensure the rework effect of the PCB board.

[0038] As attached Figure 1As shown, the present application provides a rework method for a PCB board with a poor dry film, comprising the following steps:

[0039] S1: The PCB to be reworked is fully exposed in a film-free tool environment.

[0040] During exposure, the dry film that needs to remain on the board will undergo a cross-linking reaction after being exposed to ultraviolet light. It will not be removed during the subsequent development process, and the unexposed part will be dissolved and washed away by the sodium carbonate solution, thus forming a circuit pattern. The film stripping process in the normal production process removes the dry film that has been exposed to form a pattern. Generally, NaOH solution is used for stripping. Small pieces of dry film scraps will be formed during the film stripping process. The film stripping tank is much more alkaline than the developing tank.

[0041] When reworking and stripping the dry film, the board is a board with a defective film laminating process or exposure process, so there are parts on the board that are not exposed to ultraviolet light. The conventional stripping solution is to directly pass through the film stripping tank, but when the unexposed dry film is directly immersed in a strong alkaline NaOH solution, it cannot be gradually dissolved in the sodium carbonate solution like development, but instead forms a sticky dry film residual glue substance all at once, which adheres to the hole during the stripping process and affects the quality of the hole wall. For boards with a high aspect ratio, when the dry film is rewashed, the small holes are more likely to be blocked by this dry film residual glue.

[0042] Before stripping, the whole board is exposed first. Because there is no film tool, the whole board surface is exposed to ultraviolet light, and a cross-linking reaction occurs. There is no unexposed dry film on the board surface, so when the next step of stripping is performed, no sticky dry film residue will be produced. In this application, because the whole board is exposed without film tools before demolding, it is ensured that there is no unexposed dry film residue on the class, so the subsequent stripping and washing dry film process is also different from the existing process. After the PCB board is fully exposed, the subsequent stripping and washing dry film process is faster and the stripping effect is better.

[0043] S2: De-cleaning dry film, de-cleaning dry film specifically includes:

[0044] S21: Alkaline solution spray cleaning; the alkali solution used for alkali solution spraying is sodium hydroxide solution, and the concentration of sodium hydroxide solution is 2-4wt%. The temperature of alkali solution spraying is less than 50℃, the production line running speed is 3-4m / min, and the spraying pressure is 2.5±1kg / cm 2 .

[0045] The PCB board after exposure in this application does not need to pass through the film stripping tank, and can be directly cleaned by spraying alkali solution. The spray cleaning process can be started during the transportation of the PCB board.

[0046] S22: New liquid spray cleaning; the new liquid used for new liquid spray cleaning includes the following weight components: 5-10 parts of sodium laureth sulfate, 10-15 parts of triethanolamine and 75-80 parts of water; the spray pressure during new liquid spray cleaning is 1.5±0.5kg / cm 2 .

[0047] The present application newly adds a new liquid spray cleaning process, wherein the new liquid contains sodium laureth sulfate and triethanolamine, wherein sodium laureth sulfate has a high active matter content, is not affected by water hardness, and has excellent biodegradability and low-temperature properties; triethanolamine can be used as a surfactant in combination with sodium laureth sulfate to ensure that the new liquid spray cleaning process can effectively remove residual dry film on the PCB board.

[0048] S23: Flushing sewage; flushing sewage is carried out with overflow water, and the overflow water flow rate is 4±2L / min.

[0049] S24: First overflow water washing; spray pressure is 1.5±0.5kg / cm 2 , the overflow water flow rate is 6±2L / min. Using overflow water to flush can ensure the fluidity of the flushing liquid and further ensure the cleaning effect.

[0050] S25: Acid spray cleaning; the acid used in the acid spray cleaning is 3.0±2wt% sulfuric acid solution, and the spray pressure is 1.5±0.5kg / cm 2 The pickling step of the present application can remove oxides and impurities on the copper surface and can erode trace amounts of metallic copper, thereby changing the copper surface structure to increase the copper surface uniformity, roughness and activity, thereby facilitating the next process operation.

[0051] S26: Second overflow water washing; spray pressure is 1.5±0.5kg / cm 2 , the overflow water flow rate is 6±2L / min. Using overflow water to flush can ensure the fluidity of the flushing liquid and further ensure the cleaning effect.

[0052] S27: High-pressure water washing; the spray pressure of high-pressure water washing is 12±3kg / cm 2 The high-pressure water flow can quickly and effectively remove residual impurities on the PCB board.

[0053] S28: The third overflow water wash; the spray pressure is 1.5±0.5kg / cm 2 , the overflow water flow rate is 6±2L / min. Using overflow water to flush can ensure the fluidity of the flushing liquid and further ensure the cleaning effect.

[0054] S29: Drying; the drying temperature is 90±5℃, and the air knife pressure is ≥5kpa.

[0055] The above-mentioned de-cleaning dry film process of the present application can be repeated twice, that is, step S2 is repeated twice, and the cleaning effect is better. Of course, the above-mentioned de-cleaning dry film process of the present application can also be repeated multiple times. After testing, the efficiency and quality of the PCB board after two repetitions are in the best state. Multiple repetitions are helpful to improve the quality of the PCB board, but it will affect the efficiency and cost.

[0056] In the present application, the stripping process is completed on the assembly line, and the stripping dry film can be completed during the transmission of the PCB board, thereby realizing batch rework of the PCB board. An overflow water washing process is interspersed between the alkaline cleaning, the new liquid cleaning and the acid cleaning to further ensure the stripping effect.

[0057] After the rework of the PCB board, there is no foreign matter in the hole of the PCB board, and the dry film is cleanly removed and washed, which will not affect the subsequent further process. Compared with the PCB board directly passing through the film removal cylinder in the prior art, it is cleaner and can achieve mass production with higher efficiency.

[0058] It can be understood that the above embodiments only express the preferred implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the patent scope of the present invention. It should be pointed out that, for ordinary technicians in this field, the above technical features can be freely combined without departing from the concept of the present invention, and several deformations and improvements can be made, which all belong to the protection scope of the present invention. Therefore, all equivalent changes and modifications made to the scope of the claims of the present invention should belong to the coverage of the claims of the present invention.

Claims

1. A rework method for a poor dry film on a PCB, characterized in that: The steps include: S1: The PCB to be reworked is fully exposed in a film-free tool environment; Make sure the entire board surface is exposed to UV light to cause cross-linking reaction, and there is no unexposed dry film on the board surface; S2: stripping and washing the dry film, wherein the stripping and washing dry film sequentially comprises: alkali solution spray washing, new liquid spray washing, acid solution spray washing, water washing and drying; the alkali solution used in the alkali solution spraying is sodium hydroxide solution, and the concentration of the sodium hydroxide solution is 2-4wt%; the new liquid used in the new liquid spray washing comprises the following weight components: 5-10 parts of sodium lauryl polyether sulfate, 10-15 parts of triethanolamine and 75-80 parts of water; the spray pressure of the new liquid spray washing is 1.5±0.5kg / cm 2 ; The de-cleaning dry film includes: S21: alkali solution spray cleaning; S22: new liquid spray cleaning; S23: flushing sewage; S24: first overflow water washing; S25: Acid spray cleaning; the acid used in the acid spray cleaning is 3.0±2wt% sulfuric acid solution, and the spray pressure is 1.5±0.5kg / cm 2 ; S26: second overflow water washing; S27: high pressure water washing; S28: third overflow water washing; S29: Drying.

2. A rework method for a defective dry film on a PCB according to claim 1, characterized in that: The temperature of the alkali solution during spraying is less than 50°C, the production line running speed is 3-4m / min, and the spraying pressure is 2.5±1kg / cm 2 .

3. A rework method for a defective dry film on a PCB according to claim 1, characterized in that: The parameters of the first overflow water washing, the second overflow water washing and the third overflow water washing are the same, and the spray pressure is 1.5±0.5kg / cm 2 , the overflow water flow rate is 6±2L / min.

4. A rework method for a defective dry film on a PCB according to claim 1, characterized in that: The spray pressure of the high pressure water washing is 12±3kg / cm 2 .

5. A rework method for a defective dry film on a PCB according to claim 1, characterized in that: The drying temperature is 90±5°C and the air knife pressure is ≥5kpa.

6. A rework method for a defective dry film on a PCB according to claim 1, characterized in that: In step S23, the sewage is flushed using overflow water, and the overflow water flow rate is 4±2 L / min.

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