ELECTRICALLY CONDUCTIVE ADHESIVE, ELECTRONIC CIRCUIT USING THE SAME, AND METHOD FOR MANUFACTURING SUCH ELECTRONIC CIRCUIT

Abstract

Objects of the present invention are to provide an electrically conductive adhesive which is capable of suppressing a rise in an electric resistance value of a joining part between an electronic component and a substrate under high temperature and high humidity while a specific resistance value is suppressed to be low; an electronic circuit using such electrically conductive adhesive; and a method for manufacturing such electronic circuit. According to the present invention, provided is the electrically conductive adhesive which includes an electrically conductive filler, a surface of the electrically conductive filler being a coating layer including silver, a compounded amount of the electrically conductive filler being 29.0 vol. % to 63.0 vol. % with respect to the electrically conductive adhesive, a compounded amount of the silver being 3.5 vol. % to 7.0 vol. % with respect to the electrically conductive adhesive. In addition, also provided are an electronic circuit using the electrically conductive adhesive of the present invention and a method for manufacturing such electronic circuit.

Claims

1. An electrically conductive adhesive including an electrically conductive filler, a surface of the electrically conductive filler being a coating layer including silver, a compounded amount of the electrically conductive filler being 29.0 vol. % to 63.0 vol. % with respect to the electrically conductive adhesive, a compounded amount of the silver being 3.5 vol. % to 7.0 vol. % with respect to the electrically conductive adhesive.

2. The electrically conductive adhesive according to claim 1, wherein the electrically conductive filler has a core comprising at least one kind selected from the group consisting of metal baser than the silver and a ceramic.

3. The electrically conductive adhesive according to claim 1, wherein the electrically conductive filler has a core comprising at least one kind selected from the group consisting of alumina, silica, copper, and aluminum.

4. The electrically conductive adhesive according to claim 1, wherein the electrically conductive adhesive is in an ink state.

5. An electronic circuit, wherein a semiconductor device, a thermoelectric element, a chip component, an LED component, or an electric component in which the semiconductor device, the thermoelectric element, the chip component, and the LED component are combined is electrically joined onto a resin substrate having an electrically conductive part by the electrically conductive adhesive according to claim 1.

6. The electronic circuit according to claim 5, wherein the electrically conductive part of the resin substrate is made of aluminum or copper.

7. A method for manufacturing an electronic circuit, wherein a method for applying the electrically conductive adhesive according to claim 1 onto a resin substrate having an electrically conductive part is any one of dispensing, screen printing, and gravure printing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1 is a schematic drawing schematically showing a circuit board for measuring a resistance value.

DESCRIPTION OF EMBODIMENT

[0033] Hereinafter, with reference to the accompanying drawings, an electrically conductive adhesive, an electronic circuit using such electrically conductive adhesive, and a method for manufacturing such electronic circuit according to one embodiment of the present invention will be described in detail. Note that the present invention is not limited to an embodiment set forth below and a variety of modifications can be made without departing from the technical ideas of the present invention.

EXAMPLES

1. Preparation of Electrically Conductive Adhesives

[0034] Electrically conductive adhesives according to one embodiment of the present invention and electrically conductive adhesives in Comparative Examples were prepared by using the following materials and under the following conditions (refer to “Table 1”).

Example 1

[0035] 2 g (9.6 vol. % with respect to the prepared electrically conductive adhesive and hereinafter, a compounded amount of each material is written jointly along with “vol. %” with respect to the same criterion) of an epoxy resin (a product name “EP49-10N” manufactured by ADEKA Corporation); 6 g (30.0 vol. %) of an epoxy resin (a product name “EP-4088S” manufactured by ADEKA Corporation); 1.38 g (8.5 vol. %) of a reactive diluent (a product name “EPIOL B” manufactured by NOF CORPORATION); 1.41 g (5.8 vol. %) of a curing accelerator (a product name: “SAN-AID SI-100L” manufactured by SANSHIN CHEMICAL INDUSTRY CO., LTD.); and as an electrically conductive filler, 39.5 g (46.1 vol. %) of blockish silver plating alumina powder (a product name “TFM-L05B”, an average particle diameter (D.sub.50): 5 μm, a silver content (a coating amount): 13.9 vol. % (6.4 vol. % with respect to the prepared electrically conductive adhesive), manufactured by Toyo Aluminium K.K.) were blended in a disposable cup having a capacity of 200 ml and were evenly mixed by a spatula and thereafter, were further mixed by using a three roll mill (a product name “EXAKT 80S PLUS” manufactured by Nagase Screen Printing Research Co., Ltd.) with roll spacings of 0.05 mm and 0.03 mm, thereby preparing an electrically conductive adhesive in Example 1.

Example 2

[0036] An electrically conductive adhesive in Example 2 was prepared under the same conditions as those in Example 1 such as compounded amounts (g) of components except that the electrically conductive filler was changed to spherical silver plating silica powder (a product name: “TFM-S02P”, an average particle diameter (D.sub.50): 2 μm, a silver content (a coating amount): 8.3 vol. % (5.1 vol. % with respect to the prepared electrically conductive adhesive), manufactured by Toyo Aluminium K.K.) in an amount of 43.8 g (61.1 vol. % with respect to the prepared electrically conductive adhesive).

[0037] In other words, 2 g (6.9 vol. %) of an epoxy resin A (a product name: “EP49-10N” manufactured by ADEKA Corporation); 6 g (21.7 vol. %) of an epoxy resin B (a product name “EP-40885” manufactured by ADEKA Corporation); 1.38 g (6.1 vol. %) of a reactive diluent (a product name “EPIOL B” manufactured by NOF CORPORATION); 1.41 g (4.2 vol. %) of a curing accelerator (a product name: “SAN-AID SI-100L manufactured by SANSHIN CHEMICAL INDUSTRY CO., LTD.); and as an electrically conductive filler, 43.8 g (61.1 vol. %) of spherical silver plating silica powder (a product name: “TFM-S02P”, an average particle diameter (D.sub.50): 2 μm, a silver content (a coating amount): 8.3 vol. % (5.1 vol. % with respect to the prepared electrically conductive adhesive), manufactured by Toyo Aluminium K.K.) were blended in a disposable cup having a capacity of 200 ml and were evenly mixed by a spatula and thereafter, were further mixed by using a three roll mill (a product name: “EXAKT 80S PLUS” manufactured by Nagase Screen Printing Research Co., Ltd.) with roll spacings of 0.05 mm and 0.03 mm, thereby preparing the electrically conductive adhesive in Example 2.

Example 3

[0038] An electrically conductive adhesive in Example 3 was prepared under the same conditions as those in Example 1 such as compounded amounts (g) of components except that the curing accelerator was changed to a curing accelerator with a product name SAN-AID SI-150L (manufactured by SANSHIN CHEMICAL INDUSTRY CO., LTD.) in an amount of 1.41 g (5.7 vol. % with respect to the prepared electrically conductive adhesive).

Example 4

[0039] An electrically conductive adhesive in Example 4 was prepared under the same conditions as those in Example 2 such as compounded amounts (g) of components except that the compounded amount of the spherical silver plating silica powder as the electrically conductive filler (a product name “TFM-S02P”, an average particle diameter (D.sub.50): 2 μm, a silver content (a coating amount): 8.3 vol. % (3.8 vol. % with respect to the prepared electrically conductive adhesive) manufactured by Toyo Aluminium K.K.) was changed to 23.5 g (45.7 vol. % with respect to the prepared electrically conductive adhesive).

Example 5

[0040] An electrically conductive adhesive in Example 5 was prepared under the same conditions as those in Example 1 such as compounded amounts (g) of components except that the compounded amount of the blockish silver plating alumina powder as an electrically conductive filler (a product name “TFM-L05B”, an average particle diameter (D.sub.50): 5 μm, a silver content (a coating amount): 13.9 vol. % (6.8 vol. % with respect to the prepared electrically conductive adhesive) manufactured by Toyo Aluminium K.K.) was changed to 45.0 g (49.3 vol. % with respect to the prepared electrically conductive adhesive).

Example 6

[0041] An electrically conductive adhesive in Example 6 was prepared under the same conditions as those in Example 1 such as compounded amounts (g) of components except that the compounded amount of the blockish silver plating alumina powder as the electrically conductive filler (a product name: “TFM-L05B”, an average particle diameter (D.sub.50): 5 μm, a silver content (a coating amount): 13.9 vol. % (5.9 vol. % with respect to the prepared electrically conductive adhesive) manufactured by Toyo Aluminium K.K.) was changed to 35.0 g (43.0 vol. % with respect to the prepared electrically conductive adhesive).

Example 7

[0042] An electrically conductive adhesive in Example 7 was prepared under the same conditions as those in Example 2 such as compounded amounts (g) of components except that the resin was changed to a resin with a product name AER8000 (manufactured by Asahi Kasei Corp.) in an amount of 8 g (27.4 vol. % with respect to the prepared electrically conductive adhesive).

Example 8

[0043] An electrically conductive adhesive in Example 8 was prepared under the same conditions as those in Example 1 such as compounded amounts (g) of components except that the electrically conductive filler was changed to flaky silver plating copper flakes (a product name: “TFM-C05F” (an average particle diameter (D.sub.50): 5 μm, a silver content (a coating amount): 16.8 vol. % (5.3 vol. % with respect to the prepared electrically conductive adhesive) manufactured by Toyo Aluminium K.K.) in an amount of 39.5 g (30.8 vol. % with respect to the prepared electrically conductive adhesive).

Example 9

[0044] An electrically conductive adhesive in Example 9 was prepared under the same conditions as those in Example 1 such as compounded amounts (g) of components except that the electrically conductive filler was changed to spherical silver plating aluminum powder (a product name “TFM-A05P” (an average particle diameter (D.sub.50): 5 μm, a silver content (a coating amount): 10.0 vol. % (5.3 vol. % with respect to the prepared electrically conductive adhesive) manufactured by Toyo Aluminium K.K.) in an amount of 39.5 g (53.5 vol. % with respect to the prepared electrically conductive adhesive) and the curing accelerator was changed to a curing accelerator (a product name “SAN-AID SI-100L” manufactured by SANSHIN CHEMICAL INDUSTRY CO., LTD.) in an amount of 1.65 g (5.8 vol. %).

Comparative Example 1

[0045] An electrically conductive adhesive in Comparative Example 1 was prepared under the same conditions as those in Example 1 such as compounded amounts (g) of components except that the electrically conductive filler was changed to silver particles (a product name “AgC104WR” manufactured by FUKUDA METAL FOIL & POWDER CO., LTD.) in an amount of 20 g (16.5 vol. % with respect to the prepared electrically conductive adhesive).

Comparative Example 2

[0046] An electrically conductive adhesive in Comparative Example 2 was prepared under the same conditions as those in Example 1 such as compounded amounts (g) of components except that the electrically conductive filler was changed to silver particles (a product name “AgC104WR” manufactured by FUKUDA METAL FOIL & POWDER CO., LTD.) in an amount of 30 g (22.9 vol. % with respect to the prepared electrically conductive adhesive).

Comparative Example 3

[0047] An electrically conductive adhesive in Comparative Example 3 was prepared under the same conditions as those in Example 1 such as compounded amounts (g) of components except that the electrically conductive filler was changed to silver particles (a product name “AgC104WR” manufactured by FUKUDA METAL FOIL & POWDER CO., LTD.) in an amount of 88.0 g (46.5 vol. % with respect to the prepared electrically conductive adhesive).

Comparative Example 4

[0048] An electrically conductive adhesive in Comparative Example 4 was prepared under the same conditions as those in Example 2 such as compounded amounts (g) of components except that the compounded amount of the spherical silver plating silica powder as the electrically conductive filler (a product name: “TFM-S02P”, an average particle diameter (D.sub.50): 2 μm, a silver content (a coating amount): 8.3 vol. % (5.4 vol. % with respect to the prepared electrically conductive adhesive) manufactured by Toyo Aluminium K.K.) was changed to 51.1 g (64.7 vol. % with respect to the prepared electrically conductive adhesive).

Comparative Example 5

[0049] An electrically conductive adhesive in Comparative Example 5 was prepared under the same conditions as those in Example 1 such as compounded amounts (g) of components except that the electrically conductive filler was changed to flaky silver plating copper flakes (a product name: “TFM-C05F” (an average particle diameter (D.sub.50): 5 μm, a silver content (a coating amount): 16.8 vol. % (4.4 vol. % with respect to the prepared electrically conductive adhesive) manufactured by Toyo Aluminium K.K.) in an amount of 30.0 g (25.3 vol. % with respect to the prepared electrically conductive adhesive).

[0050] The compounded amounts (vol. %) (g) of the components blended in the electrically conductive adhesives Examples 1 to 9 and Comparative Examples 1 to 5 are shown in Table 1.

TABLE-US-00001 TABLE 1 Electrically conductive filler Silver content with respect to Resin A Compounded amount adhesive Compounded amount Resin B Kind (Vol %) (g) (Vol %) Kind (g) (Vol %) Kind Example 1 Silver plating 46.1 39.5 6.4 EP49-10N 2.0 9.6 EP-4088S alumina powder (TFM-L05B) Example 2 Silver plating 61.1 43.8 5.1 EP49-10N 2.0 6.9 EP-4088S silica powder (TFM-S02P) Example 3 Silver plating 46.1 39.5 6.4 EP49-10N 2.0 9.6 EP-4088S alumina powder (TFM-L05B) Example 4 Silver plating 45.7 23.5 3.8 EP49-10N 2.0 9.6 EP-4088S silica powder (TFM-S02P) Example 5 Silver plating 49.3 45.0 6.8 EP49-10N 2.0 9.0 EP-4088S alumina powder (TFM-L05B) Example 6 Silver plating 43.0 35.0 5.9 EP49-10N 2.0 10.1 EP-4088S alumina powder (TFM-L05B) Example 7 Silver plating 62.1 43.8 5.2 AER8000 8.0 27.4 — silica powder (TFM-S02P) Example 8 Silver plating 30.8 39.5 5.3 EP49-10N 2.0 12.3 EP-4088S copper flakes (TFM-C05F) Example 9 Silver plating 53.5 39.5 5.3 EP49-10N 2.0 8.1 EP-4088S aluminum powder (TFM-A05B) Comparative Silver powder 16.5 20.0 16.5 EP49-10N 2.0 14.8 EP-4088S Example 1 (AgC104WR) Comparative Silver powder 22.9 30.0 22.9 EP49-10N 2.0 13.7 EP-4088S Example 2 (AgC104WR) Comparative Silver powder 46.5 88.0 46.5 EP49-10N 2.0 9.5 EP-4088S Example 3 (AgC104WR) Comparative Silver plating 64.7 51.1 5.4 EP49-10N 2.0 6.3 EP-4088S Example 4 silica powder (TFM-S02P) Comparative Silver plating 25.3 30.0 4.4 EP49-10N 2.0 13.2 EP-4088S Example 5 copper flakes (TFM-C05F) Resin B Reactive diluent Curing accelerator Compounded amount Compounded amount Compounded amount Total (g) (Vol %) Kind (g) (Vol %) Kind (g) (Vol %) (Vol %) Example 1 6.0 30.0 EPIOL B 1.38 8.5 SI-100L 1.41 5.8 100.0 Example 2 6.0 21.7 EPIOL B 1.38 6.1 SI-100L 1.41 4.2 100.0 Example 3 6.0 30.1 EPIOL B 1.38 8.5 SI-150L 1.41 5.7 100.0 Example 4 6.0 30.2 EPIOL B 1.38 8.6 SI-100L 1.41 5.9 100.0 Example 5 6.0 28.2 EPIOL B 1.38 8.0 SI-100L 1.41 5.5 100.0 Example 6 6.0 31.7 EPIOL B 1.38 9.0 SI-100L 1.41 6.2 100.0 Example 7 — — EPIOL B 1.38 6.2 SI-100L 1.41 4.3 100.0 Example 8 6.0 38.5 EPIOL B 1.38 10.9 SI-100L 1.41 7.5 100.0 Example 9 6.0 25.4 EPIOL B 1.38 7.2 SI-100L 1.65 5.8 100.0 Comparative 6.0 46.5 EPIOL B 1.38 13.1 SI-100L 1.41 9.1 100.0 Example 1 Comparative 6.0 42.9 EPIOL B 1.38 12.1 SI-100L 1.41 8.4 100.0 Example 2 Comparative 6.0 29.8 EPIOL B 1.38 8.4 SI-100L 1.41 5.8 100.0 Example 3 Comparative 6.0 19.7 EPIOL B 1.38 5.5 SI-100L 1.41 3.8 100.0 Example 4 Comparative 6.0 41.6 EPIOL B 1.38 11.8 SI-100L 1.41 8.1 100.0 Example 5

2. Measurement of Resistance Value

[0051] As shown in FIG. 1, an aluminum etching circuit board (9 μm-thick aluminum foil/250 μm-thick PET film) or a copper etching circuit board (12 μm-thick copper foil/250 μm-thick PET film), whose line width of foil was 5 mm, length of the foil was 10 mm, and distance between pieces of the foil was 10 mm, was prepared and by using a screen printing machine (DP-320 type screen printer manufactured by NEWLONG SEIMITSU KOGYO CO., LTD.), a 2.5 mm-wide×50 μm-thick or less electrically conductive adhesive was printed in such a way that each of the electrically conductive adhesives in Examples 1 to 10 and Comparative Examples 1 to 5 crossed on an aluminum etching circuit or a copper etching circuit.

[0052] After printing, each of the electrically conductive adhesives was cured at a temperature of 150° C. for a period of 30 minutes and by using a resistance meter (a device name “3541 9771 pin type lead” manufactured by HIOKI E.E. CORPORATION), a change in a resistance value between a and b (FIG. 1) at the lapse of zero hour, 100 hours, 200 hours, 300 hours, 400 hours, and 500 hours under a high-temperature and high-humidity environment at 85° C. and 85% was measured. Specifically, the pin type lead was brought in contact with an electrically conductive body (aluminum foil or copper foil) which was a circuit wire and each resistance value was measured.

[0053] Note that the measurement of the resistance value using the aluminum etching circuit board was conducted as to each of the electrically conductive adhesives in Examples 1 to 9 and Comparative Examples 1 to 5. In addition, since the measurement of the resistance value using the copper etching circuit board was conducted as to only the electrically conductive adhesive in Example 3, a measurement method and measurement results of this resistance value are shown as those in “Example 10”.

3. Measurement of Specific Resistance Value

[0054] For measurement of each specific resistance value, as to each sample obtained by applying each of the electrically conductive adhesives in Examples 1 to 9 and Comparative Examples 1 to 5 onto the PET film by using an applicator in such a way that a thickness thereof after drying was 30 μm to 40 μm and by conducting curing at a temperature of 150° C. for a period of 30 minutes, any three points thereof at the lapse of zero hour and 500 hours were measured by using a four probe type surface resistance meter (a product name “Loresta-GP” manufactured by Mitsubishi Chemical Analytech) and an average thereof was defined as a specific resistance value (Ω.Math.cm). Specifically, data of dimensions of the electrically conductive coating film, an average coating film thickness, and coordinates of the measurement points was inputted into the four probe type surface resistance meter, and each value obtained by causing the four probe type surface resistance meter to perform automatic calculation was defined as the specific resistance value of the electrically conductive coating film. Note that it is shown that the smaller the specific resistance value is, the more excellent electrical conductivity is. In addition, an adhesive thickness was measured by a digimatic standard outside micrometer (a product name “IP65 COOLANT PROOF Micrometer” manufactured by Mitutoyo Corporation) and confirmation was thereby made.

4. Measurement of Viscosity

[0055] A viscosity of each of the electrically conductive adhesives in Examples 1 to 9 and Comparative Examples 1 to 5 was measured by a B type viscometer (Model No.: DV2THBCJ0 manufactured by AMETEK Brookfield) at a temperature of 25° C. and at a revolving speed of 2.5 rpm.

[0056] Measurement results of the viscosity of each of the electrically conductive adhesives in Examples 1 to 10 and Comparative Examples 1 to 5, the specific resistance value thereof, and the resistance value thereof under a constant-temperature and constant-humidity environment at 85° C. and 85% are shown in Table 2.

TABLE-US-00002 TABLE 2 Specific resistance Resistance value (Ω) value Kind of Viscosity (Ω .Math. cm) circuit (Pa .Math. s) 0 hour 500 hours board 0 hour 100 hours 200 hours 300 hours 400 hours 500 hours Example 1 20.1 5.0 × 10.sup.−4 3.3 × 10.sup.−4 Aluminum 0.68 0.85 1.48 1.98 2.07 5.00 Example 2 56.2 3.3 × 10.sup.−4 5.3 × 10.sup.−4 Aluminum 0.49 1.77 2.45 3.69 5.62 9.95 Example 3 17.4 6.7 × 10.sup.−4 8.2 × 10.sup.−4 Aluminum 0.96 1.31 2.99 1.99 2.51 3.29 Example 4 11.1 8.1 × 10.sup.−4 1.0 × 10.sup.−3 Aluminum 1.29 10.92 18.36 40.21 219.64 1345.99 Example 5 22.2 2.6 × 10.sup.−4 3.2 × 10.sup.−4 Aluminum 0.84 1.24 1.83 2.61 3.28 3.72 Example 6 15.6 4.2 × 10.sup.−4 5.1 × 10.sup.−4 Aluminum 0.74 0.89 0.98 1.03 1.13 1.35 Example 7 83.4 5.0 × 10.sup.−4 6.0 × 10.sup.−4 Aluminum 0.88 2.49 3.32 8.24 13.27 18.16 Example 8 42.4 2.4 × 10.sup.−3 3.7 × 10.sup.−3 Aluminum 0.76 0.91 1.04 1.13 1.21 1.28 Example 9 34.1 5.0 × 10.sup.−4 4.3 × 10.sup.−4 Aluminum 0.68 2.53 3.68 2.00 1.54 1.84 Example 10 Same as in Same as in Same as in Copper 0.86 0.98 1.04 1.08 1.07 1.03 Example 3 Example 3 Example 3 Comparative 17.2 4.6 × 10.sup.−4 3.8 × 10.sup.−4 Aluminum 5.13 8.52 15.55 70.68 — — Example 1 Comparative 43.7 2.3 × 10.sup.−3 6.6 × 10.sup.−4 Aluminum 5.11 — — — — — Example 2 Comparative Unable to be 2.9 × 10.sup.−2 — Aluminum 76.70 — — — — — Example 3 measure Comparative Unable to be — — Aluminum Impossible to be measured since kneading was unable. Example 4 kneaded Comparative 21.5 1.5 × 10.sup.−1 — Aluminum Impossible to be measured since the specific resistance value was excessively high. Example 5 .sup.※ The electrically conductive adhesive in “Example 10” was the same as the electrically conductive adhesive in Example 3 and in Example 10, the copper circuit board used upon measuring the resistance value was used.

5. Discussion

[0057] As shown in Table 2, in a case of the electrically conductive adhesives in Comparative Examples 1 and 2, in each of which as the electrically conductive filler, the silver particles themselves were used, obtained were results in that as to the electrically conductive adhesive in Comparative Example 1, the resistance value increased until it was impossible to measure the resistance value at the lapse of 400 hours, and as to the electrically conductive adhesive in Comparative Example 2, the resistance value increased until it was impossible to measure the resistance value at the lapse of 100 hours. As described above, it was confirmed that although in the case where as the electrically conductive filler, the silver particles themselves were used, it was effective to suppress the specific resistance value to be low, a rise in the electric resistance value of the joining part between the electronic component and the substrate under high temperature and high humidity was incurred.

[0058] In addition, it was found from Table 2 that when the electrically conductive adhesives in Examples 1 to 10 and Comparative Examples 1 to 5 were compared, when the added amount of the electrically conductive filler was smaller than 29.0 vol. %, the resistance value increased and when the added amount of the electrically conductive filler was larger than 63.0 vol. %, the viscosity of the electrically conductive adhesive increased, thereby making kneading or discharging upon dispensing difficult. Therefore, it was preferable that the added amount of the electrically conductive filler into the adhesive was 29.0 vol. % to 63.0 vol. % when a total volume of the electrically conductive adhesive was 100 vol. %.

[0059] Furthermore, it was found that when the silver content in the electrically conductive filler was smaller than 3.5 vol. % with respect to the electrically conductive adhesive, the resistance value increased and when the silver content therein was larger than 7.0 vol. % with respect thereto, with the lapse of time, it became impossible to suppress the rise in the electric resistance value of the joining part between the electronic component and the substrate. Therefore, it was preferable that the silver content in the electrically conductive filler was 3.5 vol. % to 7.0 vol. % when the total volume of the electrically conductive adhesive was 100 vol. %.

REFERENCE SIGNS LIST

[0060] 1: Circuit board

[0061] 2: Electrically conductive adhesive

[0062] a to e: Circuit

[0063] X: Circuit width

[0064] Y: Circuit spacing

[0065] L: Circuit length