JP4640557B2 - Etching accuracy evaluation method - Google Patents

Description

【００２８】
また、基板サイズ５１０×５１０ｍｍで厚さ０．８ｍｍ（銅厚片面３５μｍ）の両面銅張積層板に、エッチングレジストを４０μｍ厚に塗布し、この基板の両面に図１，２に示したテストパターン２を露光・現像してテスト基板を得、このテスト基板を塩銅エッチャントのエッチングラインにて、搬送速度３．６ｍｍ／ｍｉｎ，ライン滞留時間１４６ｓｅｃの条件でエッチングした後、線幅１００μｍの縦テストパターン２１と、線幅１００μｍの横テストパターン２２の抵抗値を測定し、上記表１の評価基準にあてはめて評価したのて、その結果を図４，５に示す。
【００２９】
図４（ａ）はテスト基板上面における縦テストパターン２１の抵抗値による評価結果で、図４（ｂ）はテスト基板下面における縦テストパターン２１の抵抗値による評価結果である。また、図５（ａ）はテスト基板上面における横テストパターン２２の抵抗値による評価結果で、図５（ｂ）はテスト基板下面における横テストパターン２２の抵抗値による評価結果である。
【００３０】
なお、抵抗測定は任意の方法によってよいが、例えばピンボード式もしくはＸ−Ｙ式などの回路基板検査機を用いることにより、各テストパターンの抵抗値を高速度に測定することができる。
【００３１】
また、テストパターンの線幅は、製品基板に合わせて任意に選択されてよい。
上記実施形態では、各テストパターンの抵抗値を引出電極間で測定するようにしいるが、場合によっては、一方の引出電極と中継電極との間の抵抗を測定するようにしてもよい。
【００３２】
【発明の効果】
以上説明したように、本発明によれば、エッチングにより形成された回路パターンの所定の２点間の抵抗値を測定し、その抵抗値をパターン幅に換算して回路パターンの仕上がり状態を判定するようにしたことにより、短時間でエッチング精度を評価することができる。
【図面の簡単な説明】
【図１】本発明の実施形態としてのテスト基板の上面側を示した平面図。
【図２】上記テスト基板の下面側を示した平面図。
【図３】上記テスト基板に設けられている抵抗測定用テストパターンの拡大平面図。
【図４】上記テスト基板の評価結果を示した説明図。
【図５】上記テスト基板の評価結果を示した説明図。
【符号の説明】
１ テスト基板
２ 抵抗測定用テストパターン
２１ 線幅１００μｍの縦テストパターン
２２ 線幅１００μｍの横テストパターン
２３ 線幅７５μｍの横テストパターン
２４ 線幅７５μｍの縦テストパターン
２５１，２５２，２６１，２６２ 引出電極
２５３，２６３ 中継電極[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for evaluating etching accuracy of a printed circuit board and a test substrate thereof, and more particularly, to a technique that can perform etching accuracy evaluation for the entire surface of the substrate in a short time with high accuracy.
[0002]
[Prior art]
With the demand for miniaturization of equipment, circuit patterns have been increasingly refined, and in recent years, the pattern width has been required to be several tens of microns. A circuit pattern is roughly divided and formed through an etching resist forming process, an exposure / development process, an etching process, and a cleaning process, and the etching process is particularly related to the finished state of the circuit pattern.
[0003]
That is, in the etching process, while the circuit board is sent at a predetermined conveyance speed, the etching solution is sprayed from the nozzles on both the front and back surfaces to remove unnecessary copper foil portions, but the conveyance speed (process residence time) Etching accuracy depends on the composition of the etching solution.
[0004]
Therefore, etching process control is extremely important. Conventionally, a test substrate is appropriately flowed through the etching line, and the pattern width is measured from the cross section as a cross section method, or the pattern width is measured with a length measuring machine. Thus, the finished state of the circuit pattern is evaluated.
[0005]
[Problems to be solved by the invention]
However, even with the same substrate, the etching accuracy differs between the front surface side and the back surface side because the amount of the etching solution sprayed and the residence time of the etching solution on the substrate surface are different. Further, even on the same surface, the etching accuracy differs between the central portion and the end portion for the same reason.
[0006]
Accordingly, it is necessary to comprehensively evaluate a single test substrate by observing a plurality of locations thereof, but the conventional method requires a lot of time, and thus a reduction in evaluation time has been demanded.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, the present invention uses a copper-clad laminated substrate having an etching resist as a test substrate, exposes and develops the same test pattern on a plurality of locations of the test substrate through a photomask, and then uses an etching solution. Remove unnecessary copper foil parts, form the same test pattern at multiple locations on the test board, measure the resistance value between the same two points for each test pattern, and convert the resistance value to the pattern width Accordingly, when evaluating the etching accuracy on the whole surface of the test substrate assuming the finished state of the circuit pattern, each test pattern includes a first test pattern and a second test pattern formed in directions orthogonal to each other. Are included as a pair, and both the first and second test patterns are the same for measuring the resistance value between the two points. A pair of lead electrodes disposed, and a relay electrode for connecting at least two wires in series between the pair of lead electrodes, between one of the lead electrode and the relay electrode above and the Between the other extraction electrode and the relay electrode, a wiring formed in a zigzag shape with a predetermined line width and an inter-line width is formed as the same pattern electrically connected. The first test pattern is arranged as a vertical pattern parallel to the transport direction with respect to the transport direction of the test substrate on the etching line for removing the copper foil portion, and the second test pattern is orthogonal to the transport direction. It is characterized by being arranged as a horizontal pattern. According to this, the finished state of the circuit pattern can be evaluated in a short time by resistance measurement.
[0009]
According to a preferred embodiment of the present invention, the upper Symbol each test pattern is regularly formed an X-Y matrix form over the entire surface of the test substrate.
[0010]
In the present invention, it is preferable that a wiring for visual observation that is not electrically connected anywhere is formed in a bar graph shape with a predetermined line width and a line width between the respective wirings. Further, the present invention includes an embodiment in which the test substrate is a double-sided substrate, and the test patterns are formed on both the front and back surfaces.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an upper surface (front surface) 1U of a test substrate 1 as an embodiment of the present invention, and FIG. 2 shows a lower surface (back surface) 1L thereof. That is, the test board 1 is a double-sided board. The same test pattern is formed in the same arrangement on the upper surface 1U and the lower surface 1L.
[0012]
In this embodiment, the test pattern includes a test pattern 2 for measuring resistance value and a test pattern 3 for measuring copper thickness. The test pattern 2 and the test pattern 3 are alternately arranged according to an XY matrix arrangement so as to be distributed over the entire surface of the test substrate 1.
[0013]
The test substrate 1 is obtained by forming an etching resist on a double-sided copper-clad laminate, exposing and developing it through a photomask having the test patterns 2 and 3, and leaving the etching resist on the test patterns 2 and 3. Has been.
[0014]
FIG. 3 shows an enlarged test pattern 2 for measuring one resistance value. The test pattern 2 includes four test patterns 21 to 24. In this embodiment, the test patterns 21 and 22 are both 100 μm in line width and line spacing, but one test pattern 21 is a vertical pattern and the other test pattern 22 is a horizontal pattern.
[0015]
In contrast, the test patterns 23 and 24 are patterns having a line width and a line spacing of 75 μm, but one test pattern 23 is a horizontal pattern and the other test pattern 24 is a vertical pattern. The vertical pattern is a pattern formed in a direction parallel to the conveyance direction in the etching line, and the horizontal pattern is a pattern formed in a direction orthogonal to the conveyance direction in the etching line. Further, the line width of each pattern and the distance between the lines may be arbitrarily selected depending on the target etching accuracy.
[0016]
The test patterns 21 and 22 have the same pattern shape except for the orientation. That is, a pair of extraction electrodes 251 and 252 arranged on the same side and a relay electrode 253 arranged between them are provided, and between the one extraction electrode 251 and the relay electrode 253, a line width of 100 μm is provided. The wiring 254 is formed in a zigzag shape.
[0017]
A wiring 255 having a line width of 100 μm is also formed in a zigzag shape between the other extraction electrode 252 and the relay electrode 253, and the extraction electrode 251 and the extraction electrode 252 are electrically Connected.
[0018]
Between the wiring 254 and the wiring 255, a wiring 256 having a line width of 100 μm and a line spacing of 100 μm is formed in a bar graph shape. The wiring 256 is for visual observation and is not connected anywhere. Note that the line width of the wiring 254 is larger than the line width of the wiring 255. This is because the relationship between the etching accuracy and the line width is observed, and the line width may change depending on the line density. Because it is expected.
[0019]
Similarly, the test patterns 23 and 24 have the same pattern shape except for the orientation. That is, a pair of extraction electrodes 261 and 262 arranged on the same side and a relay electrode 263 arranged therebetween are provided, and a line width of 75 μm is provided between one extraction electrode 261 and the relay electrode 263. The wiring 264 is formed in a zigzag shape.
[0020]
A wiring 265 having a line width of 75 μm is also formed in a zigzag shape between the other extraction electrode 262 and the relay electrode 263. The extraction electrode 261 and the extraction electrode 262 are electrically Connected.
[0021]
Between the wiring 264 and the wiring 265, a visual observation wiring 256 having a line width of 75 μm and a line spacing of 75 μm is formed in a bar graph shape. Similarly to the above, the line width of the wiring 264 is wider than the line width of the wiring 265 to see the relationship between the etching accuracy and the line width.
[0022]
The test pattern 3 for measuring the copper thickness is a solid pattern for observing the etching progress rate. In the present invention, the test pattern 3 is an optional component.
[0023]
In the present invention, the etching accuracy of the etching line is evaluated by measuring the resistance value of the test pattern 2 after flowing the test substrate 1 through the etching line in the actual process and etching it. Since the resistance value is inversely proportional to the pattern width, the pattern width can be determined from the resistance value by obtaining the relative coefficient in advance.
[0024]
When the line width of the product substrate is 100 μm, the resistance between the extraction electrodes 251 and 252 of the test patterns 21 and 22 is measured, and when the line width of the product substrate is 75 μm, the test pattern What is necessary is just to measure the resistance between the 23 and 24 extraction electrodes 261 and 262, and to evaluate the etching accuracy of the etching line which flows those product substrates.
[0025]
The coefficient is obtained as follows. For example, assuming that the resistance value of a wiring pattern having a copper thickness of 35 μm, a width of 100 μm and a predetermined length is 1.25Ω, if the measured resistance value is 1.00Ω with this as a reference value, the coefficient is 1.00. /1.25=0.800, and the line width can be estimated as 100 μm / 0.800 = 125 μm.
[0026]
If the measured resistance value is, for example, 1.67Ω, the coefficient is 1.67 / 1.25 = 1.333, and the line width can be estimated to be 100 μm / 1.333 = 1.75 μm. An example of the evaluation criteria thus obtained is shown in the following table.
[0027]
[Table 1]

[0028]
An etching resist is applied to a double-sided copper-clad laminate having a substrate size of 510 × 510 mm and a thickness of 0.8 mm (copper thickness on one side: 35 μm) to a thickness of 40 μm, and the test pattern shown in FIGS. 2 is exposed and developed to obtain a test substrate. This test substrate is etched on a salt copper etchant etching line under conditions of a conveyance speed of 3.6 mm / min and a line residence time of 146 sec, and then a vertical test with a line width of 100 μm. The resistance values of the pattern 21 and the lateral test pattern 22 having a line width of 100 μm were measured and evaluated according to the evaluation criteria shown in Table 1, and the results are shown in FIGS.
[0029]
FIG. 4A shows an evaluation result based on the resistance value of the vertical test pattern 21 on the upper surface of the test substrate, and FIG. 4B shows an evaluation result based on the resistance value of the vertical test pattern 21 on the lower surface of the test substrate. FIG. 5A shows an evaluation result based on the resistance value of the horizontal test pattern 22 on the upper surface of the test substrate, and FIG. 5B shows an evaluation result based on the resistance value of the horizontal test pattern 22 on the lower surface of the test substrate.
[0030]
The resistance may be measured by any method, but the resistance value of each test pattern can be measured at a high speed by using a circuit board inspection machine such as a pin board type or an XY type.
[0031]
Further, the line width of the test pattern may be arbitrarily selected according to the product substrate.
In the above embodiment, the resistance value of each test pattern is measured between the extraction electrodes. However, in some cases, the resistance between one extraction electrode and the relay electrode may be measured.
[0032]
【The invention's effect】
As described above, according to the present invention, the resistance value between two predetermined points of the circuit pattern formed by etching is measured, and the resistance value is converted into the pattern width to determine the finished state of the circuit pattern. By doing so, the etching accuracy can be evaluated in a short time.
[Brief description of the drawings]
FIG. 1 is a plan view showing an upper surface side of a test substrate as an embodiment of the present invention.
FIG. 2 is a plan view showing a lower surface side of the test board.
FIG. 3 is an enlarged plan view of a resistance measurement test pattern provided on the test board.
FIG. 4 is an explanatory view showing an evaluation result of the test board.
FIG. 5 is an explanatory view showing an evaluation result of the test board.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Test board 2 Resistance measurement test pattern 21 Vertical test pattern 22 with a line width of 100 μm Horizontal test pattern 23 with a line width of 100 μm Horizontal test pattern 24 with a line width of 75 μm Vertical test patterns 251, 252, 261 and 262 with a line width of 75 μm 253,263 Relay electrode

Claims (4)

Using a copper-clad laminate with an etching resist as a test substrate, exposing and developing the same test pattern on a plurality of locations on the test substrate through a photomask, and then removing unnecessary copper foil portions with an etching solution By forming the same test pattern at a plurality of locations on the substrate, measuring the resistance value between the same two points for each test pattern, and converting the resistance value to the pattern width, the entire surface of the test substrate is targeted, In evaluating the etching accuracy assuming the finished state of the circuit pattern,
Each of the test patterns includes a first test pattern and a second test pattern formed in a direction perpendicular to each other as a pair, and both the first and second test patterns measure resistance values between the two points. A pair of extraction electrodes arranged on the same side for use, and a relay electrode for connecting at least two wires in series between the pair of extraction electrodes, the one extraction electrode and the relay electrode And between the other extraction electrode and the relay electrode are formed as the same pattern in which wirings formed in a zigzag shape with a predetermined line width and inter-line width are electrically connected,
The first test pattern is arranged as a vertical pattern parallel to the transport direction with respect to the transport direction of the test substrate in the etching line for removing unnecessary copper foil portions with the etchant, and the second test pattern is An etching accuracy evaluation method, wherein the etching accuracy evaluation method is arranged as a horizontal pattern orthogonal to the transport direction.   2. The etching accuracy evaluation method according to claim 1, wherein each of the test patterns is regularly formed in an XY matrix over the entire surface of the test substrate. 2. A plurality of wirings for visual observation that are not electrically connected anywhere are formed between the wirings in parallel with each other with a predetermined line width and an inter-line width. Or the etching accuracy evaluation method according to 2 above.   4. The etching accuracy evaluation method according to claim 1, wherein the test substrate is a double-sided substrate, and the test patterns are formed on both front and back surfaces.

Images