CN106658966B

CN106658966B - Method for etching inner layer of thin film resistor

Info

Publication number: CN106658966B
Application number: CN201611111531.3A
Authority: CN
Inventors: 周文涛; 宋清; 赵波; 徐琪琳; 翟青霞
Original assignee: Shenzhen Suntak Multilayer PCB Co Ltd
Current assignee: Shenzhen Suntak Multilayer PCB Co Ltd
Priority date: 2016-12-06
Filing date: 2016-12-06
Publication date: 2020-03-17
Anticipated expiration: 2036-12-06
Also published as: CN106658966A

Abstract

The invention provides a method for etching an inner layer of a thin film resistor, which sequentially comprises the following processes: cutting → inner layer film → inner layer exposure → inner layer etching 1 → inner layer etching 2 → inner layer AOI → post-processing, wherein, only the protective film of the resistive surface is torn off when the inner layer etching 1, and the protective film without the resistive surface is torn off when the inner layer etching 2. In the scheme, the two times of etching are carried out on the same etching line, and meanwhile, different areas are protected by the protective film during etching, so that only one surface with a resistor is etched in the first time of etching, and the two surfaces of the circuit board are etched in the second time of etching. The etching method optimizes the process flow, reduces the equipment and raw material investment, effectively reduces the production cost and further improves the production efficiency.

Description

Method for etching inner layer of thin film resistor

Technical Field

The invention relates to a preparation process of a multilayer circuit board, in particular to an etching method of an inner layer of a thin film resistor.

Background

The existing production flow of etching the inner layer of the thin film resistor comprises the following steps: cutting → inner layer film → inner layer exposure → inner layer etching 1 → inner layer etching 2 → inner layer AOI, wherein when the inner layer etching 2 process flow is carried out, an etching line needs to be additionally and independently cut, and the specific flow is as follows: liquid preparation (copper sulfate) → cylinder opening → temperature rise → inner layer etching 2 (soaking), in the production process of the existing embedded resistor product, the liquid preparation is additionally needed due to etching of the resistor layer (nickel-phosphorus layer), the cylinder opening is carried out, partial flow is added, the process flow is more complex, the cost of equipment and liquid medicine is needed to be increased, and the production efficiency is greatly influenced.

Disclosure of Invention

In order to solve the technical problem, the invention discloses a thin film resistor inner layer etching method which sequentially comprises the following procedures of material cutting → inner layer film application → inner layer exposure → inner layer etching 1 → inner layer etching 2 → inner layer AOI → post-processing, wherein the protective film without the resistance surface is torn off when the inner layer etching 1 is carried out, and the protective film without the resistance surface is torn off when the inner layer etching 2 is carried out.

Further, the inner layer etching 1 process and the inner layer etching 2 process are repeated on the same etching line.

Further, the inner layer etching 1 process and the inner layer etching 2 process adopt the same etching liquid medicine, and the etching liquid medicine is hydrochloric acid solution.

Furthermore, the etching amount of the inner layer is superposed twice to be just the etching amount required by the pattern of the resistance layer, and the etching rate and time can be set according to the thickness of the resistance layer and the thickness of the copper foil.

Further, in the inner layer film pasting process, an LDI dry film is adopted, and the inner layer film pasting process needs to be kept still for 25-35 minutes.

According to the scheme, the two times of etching are carried out on the same etching line, and meanwhile, different areas are protected by the protective film during etching, so that only one surface with a resistor is etched in the first time of etching, and the two surfaces of the circuit board are etched in the second time of etching. The etching method optimizes the process flow, reduces the equipment and raw material investment, effectively reduces the production cost and further improves the production efficiency.

Drawings

The following detailed description of the invention with reference to the drawings

FIG. 1 is a process flow diagram of a method for etching an inner layer of a thin film resistor according to the present invention.

Detailed Description

In order to explain technical contents, structural features, and objects and effects of the present invention in detail, the following description is given in detail with reference to the embodiments.

With reference to fig. 1, the present disclosure relates to a method for etching an inner layer of a thin film resistor, which sequentially includes the following processes of material cutting → inner layer lamination → inner layer exposure → inner layer etching 1 → inner layer etching 2 → inner layer AOI → post-process.

Cutting, namely cutting the original circuit board core board into the required dimension by using a cutting machine according to the process requirement and the dimension specification. The cutting process is mostly the initial process of circuit board manufacturing, and in the process, the circuit board core board can be cut according to the size of the jointed board for the subsequent process manufacturing.

The inner layer film is the dry film attached to the inner layer circuit pattern. Here, an LDI (laser direct imaging) dry film is attached to the surface of the core plate as an imaging material. The dry film is generally divided into three layers, one layer is a PE protective film, the middle layer is a dry film layer, and the other layer is a PET protective layer. The PE layer and the PET layer only have to be removed before lamination and before development for protection, and the middle dry film layer is really used and has certain viscosity and good photosensitivity. After the attachment, the adhesive needs to be left standing for a period of time, generally 25 to 35 minutes, and preferably 30 minutes. Through standing after the inner layer is pasted with the film, the dry film can be well attached to the inner layer plate, so that the operation of the subsequent flow is facilitated.

And (3) exposing the inner layer, namely irradiating and exposing the film by using a 6-grid exposure ruler or a 21-grid exposure ruler, wherein the film is exposed as soon as possible after a dry film is pasted, and the photosensitive dry film has a certain quality guarantee period. The substrate covering the negative film and the dry film is irradiated with light, and the image on the negative film is reversely transferred to the dry film after exposure through image transfer. After the copper-clad plate after exposure is stood, a sodium carbonate solution can be used as bath solution for development. The unexposed part of the photosensitive film reacts with the dilute alkali solution to generate soluble substances which are dissolved, and the dry film of the exposed part is not swelled. And finally, obtaining the required inner layer circuit image.

Etching the inner layer 1, and after the inner layer is exposed and developed, etching the inner layer circuit board for the first time. The etching process can be completely carried out on the etching line in the prior art, namely, the existing etching line does not need to be modified. In the etching of the inner layer, the etching solution is hydrochloric acid solution. Namely, the exposed copper layer is removed by a chemical reaction between hydrochloric acid and base copper. However, in this etching process, only the protective film on the surface having the resistance is removed, but the protective film on the surface having no resistance is not removed, and therefore, in the etching process, the protective film is required to protect the surface having no resistance from the etching solution during the first etching, thereby preventing the underlying metal copper layer from being corroded and damaged by the etching solution. In this etching, since the protective film on the resistive surface is torn off, the thin film resistive layer and the corresponding copper foil layer covered by the protective film are exposed, hydrochloric acid in the etching solution reacts with copper in the copper foil layer and the nickel-phosphorus layer in the thin film resistive layer, the metal layer is converted into an ionic compound and enters the etching solution, and the exposed metal layer is corroded and damaged, so that the purpose of etching the copper foil layer and the resistive layer is achieved. Because the protective film of the plate surface does not react with hydrochloric acid in the etching solution, the non-resistance surface covered by the protective film cannot contact with the hydrochloric acid solution in the etching solution under the action of the protective film, and further cannot change.

And etching the inner layer 2, and performing second etching on the inner layer circuit board after the first etching. The second etching is also carried out on the etching line of the first etching, namely, the second etching is directly carried out on the original etching line without separately forming an etching line. Meanwhile, the same etching solution tank, namely hydrochloric acid solution, is adopted for the second etching. The difference is that the protective film on the side without the resistor needs to be removed in this etching, that is, in the second etching, both the resistive surface and the non-resistive surface are directly exposed to the etching solution and directly contact with the etching solution hydrochloric acid solution. And the whole inner layer circuit board can directly contact with the etching solution and carry out chemical reaction, and both the double-sided copper foil layer and the resistance nickel-phosphorus layer are etched and fall off due to the reaction with the etching solution. Here, the second etching is still performed on the etching line used for the first etching, and the etching solution used does not need to be replaced separately. The most important feature of the technical scheme is that the production cost can be greatly reduced, and the production efficiency can be greatly improved.

In addition, in the two etching processes, the etching time and etching rate are strictly required, and the etching time and etching rate of the two inner layers are different. However, in the case of the inner sheet resistor, the etching amounts of the two layers are superposed to be just the etching amount required for the resistor layer pattern. Meanwhile, the etching rate and time can be set according to the thickness of the resistor and the thickness of the copper foil so as to reach the required specification.

The inner layer AOI (Automatic optical Inspection) is called Automatic optical Inspection and is equipment for inspecting common defects encountered in welding production based on an optical principle. During automatic detection, the machine automatically scans the PCB through the camera, acquires images, compares the tested welding spots with qualified parameters in the database, inspects the defects on the PCB through image processing, displays/marks the defects through a display or an automatic mark for maintenance personnel to repair, completes the final manufacturing process of the inner layer graph, and thus, the qualified product is obtained.

The thin film resistor etching method in the scheme is characterized in that the two times of etching are repeatedly carried out on the same etching line, and meanwhile, the same etching liquid medicine is adopted for etching. In addition, different areas of the board surface are protected by the protective film during two times of etching, so that only one surface with the resistor is etched in the first etching process, and the two surfaces of the circuit board are etched in the second etching process. The etching method not only optimizes the process flow, does not need to arrange an etching line additionally, but also reduces the equipment and raw material investment, effectively reduces the production cost and further improves the production efficiency.

The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes performed by the present specification and drawings, or applied to other related technical fields directly or indirectly, are included in the scope of the present invention.

Claims

1. A method for etching an inner layer of a thin film resistor is characterized in that: the method sequentially comprises the following processes of cutting material → inner layer film → inner layer exposure → inner layer etching 1 → inner layer etching 2 → inner layer AOI → post-processing, wherein the protective film of the resistance surface is only needed to be torn off when the inner layer etching 1 is carried out, and the protective film without the resistance surface is torn off when the inner layer etching 2 is carried out; in the inner layer etching 2, the resistance surface and the non-resistance surface are directly exposed in the etching liquid and directly contacted with the etching liquid; the inner layer etching 1 process and the inner layer etching 2 process are repeatedly carried out on the same etching line; the inner layer etching 1 process and the inner layer etching 2 process adopt the same etching liquid medicine, and the etching liquid medicine is hydrochloric acid solution; and superposing the etching amount of the inner layer twice to be just the etching amount required by the resistor layer pattern, and setting the etching rate and time according to the resistor thickness and the copper foil thickness.

2. The method of etching an inner layer of a thin film resistor according to claim 1, wherein: in the inner layer film pasting process, an LDI dry film is adopted, and the inner layer film pasting process needs to be kept still for 25-35 minutes.