JPH03229497A - Recording method of identification code of printed circuit board, reading method thereof and applied device thereof - Google Patents

Abstract

PURPOSE:To enable recording of identification information in a large amount in a limited space by a method wherein a position-alignment mark in a printed circuit board is used also for recording of an identification code, and the position of the position-alignment mark for recording the paste of a printed-circuit pattern of each layer and the color tone of the pattern of each layer are selected appropriately. CONSTITUTION:In a position-alignment mark of a printed-circuit board formed by aligning, for instance, square patterns of layers of a milk-white dielectric, a black resistor and green cover glass, first the digit of a numeric is constructed of each of a plurality of square patterns 4 in a first layer conductor, and one or a plurality of square patterns S of the milk-white dielectric are aligned with the square patterns in the first-layer conductor of the digits corresponding to identification information desired to be recorded. Next, one or a plurality of square patterns 6 of the black resistor are aligned with the square patterns in the first-layer conductor of the digits corresponding to identification information desired to be recorded. Then, one or a plurality of square patterns 7 of the green cover glass are aligned with the square patterns in the first layer conductor of the digits corresponding to identification information desired to be recorded. In this way, identification codes are recorded on the position- alignment marks.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to a method for recording an identification symbol on a printed circuit board, a method for reading the same, and an application device thereof.

[Prior art] Conventionally, electronic components using printed circuit boards, such as thick-film hybrid ICs, have been identified by recording the product name and production lot in letters and numbers on the printed circuit board using printing or stamping methods. However, these methods require separate space for recording letters and numbers;
In recent years, electronic components have become increasingly smaller and more dense, and there has been a problem in that securing a recording space on the substrate is a problem. For this reason, it is not possible to place letters and numbers that record the product name and manufacturing lot in a fixed position on the printed circuit board of electronic components, making it difficult to automate the mounting line and identify the product name and manufacturing lot. , Automatically change the manufacturing conditions depending on the product name.
This was a hindrance to the realization of so-called unmanned factories.

That is, as the packaging density increases and various printed circuit boards are flown on a mounting line operated in high-mix, low-volume production, automatic board identification is required during packaging.

In other words, automatic board identification is an essential technology at production sites where unmanned robots automatically mount and connect the necessary parts to the required printed circuit boards.

In addition, related to this type of technology, for example, Utility Model Application No. 59-1 concerning a method of forming a mark such as a bar code on a part of the outer surface of a package to enable automatic identification.
31157, and Japanese Patent Laid-Open No. 60-31249 regarding the formation of an identification mark on a board for a hybrid circuit board.

[Problems to be Solved by the Invention] However, this method requires a package with an outer surface, and is generally used for printed circuit boards that do not have a flat outer surface, such as thick film hybrid ICs. It is difficult to apply. Furthermore, even when recording a barcode directly on a printed circuit board, a recording space is required, just as when recording characters and numbers.

Therefore, in order to deal with high-density packaging, the current problem to be solved is how to record a large amount of identification information in a small and limited space on a printed circuit board.

Therefore, an object of the present invention is to solve the above problems, and to provide an identification recording method, a reading method thereof, and an application device thereof, which are capable of recording a large amount of identification information in a limited and small space of a printed circuit board. It is about providing.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a plurality of, for example, one rectangular alignment pattern made of the first prefectural body,
In a printed circuit board alignment mark made by sequentially aligning, for example, rectangular patterns of each layer of a milky white dielectric, a black resistor, and a green cover glass, each of the plurality of rectangular patterns in the first prefecture constitutes a numerical digit. Then, match the rectangular pattern of one or more milky-white dielectrics to the rectangular pattern in the first prefecture of the digit corresponding to the identification information you want to record, and then match the rectangular pattern of one or more black resistors to the rectangular pattern of one or more black resistors. Align it with the rectangular pattern in the first prefecture of the digit corresponding to the identification information you want to record, and then align the rectangular pattern of one or more green cover glasses with the first digit of the digit corresponding to the identification symbol you want to record. This makes it possible to record an identification symbol on the alignment mark by matching it to a rectangular pattern within the prefecture.

That is, in this recording method, when the number of alignment marks for each layer pattern made of the U-th layer is m, and the types of color tones of each layer pattern are n types, identification information is expressed as an m-digit n-ary number. You can think about it.

Hereinafter, the means for achieving the object of the present invention will be explained in more detail.

That is, the object of the present invention is as follows: (1) an alignment reference mark made of a plurality of the conductors provided on one main surface of an insulating substrate in the same process as forming a circuit pattern made of the first prefecture body; Thereon, each of the other alignment pattern marks is sequentially provided in alignment with any of the alignment reference marks in the same process as forming each pattern of at least the dielectric, the resistor, and the cover glass. A printed circuit board is provided, the alignment reference mark is a digit display mark of a board identification symbol, and each of the other alignment pattern marks provided in accordance with the alignment reference mark is composed of patterns of different tones, and An identification record for a printed circuit board in which each color tone is used as identification information, and an identification symbol is recorded by these alignment reference marks and other alignment pattern marks of different color tones provided within the area. Also, depending on the number recording method.

(2) The shape of the alignment reference mark and each of the other alignment pattern marks of different colors is polygonal including a circle, the color tone of the dielectric body is milky white, the color tone of the resistor body is black, and the color tone of the resistor body is black; By the printing board identification symbol recording method described in (1) above, in which the glass color tone is green, and (3) each alignment pattern mark provided in the area of the alignment reference mark and having a different tone. When the number of is m and the types of color tones are n, the above (1
) or by the printing board identification symbol recording method described in (2), and (4) at least one of the other alignment pattern marks with different tones provided within the area of the alignment reference mark, The number is based on the identification mark recording method of the printed circuit board described in (1) to (3) above, in which the above-mentioned identification information can be additionally recorded by selectively irradiating laser light to remove part or all of it. ), and (5) the alignment reference mark is formed into an annular shape.

The printed circuit board identification symbol recording method described in (1) to (3) above, wherein each of the other alignment pattern marks having different color tones is formed in a shape that is fitted into the center of an annular circle of the reference mark; (6) An alignment reference mark made of a plurality of conductors provided on one main surface of the M11 substrate at the same time as the formation of the circuit pattern made of the first layer, and at least a dielectric material, a resistor material and For printing and forming a circuit pattern used in manufacturing a printed circuit board having each pattern of a cover glass formed at the same time as each other alignment pattern mark provided in accordance with any of the alignment reference marks. As a mask, either the alignment reference mark or each of the other alignment pattern marks may be formed in advance on the circuit pattern printing mask.

(7) The identification symbol of the printed circuit board on which the identification symbol has been formed and retained by the method for recording the identification symbol of the printed circuit board described in (1) to (5) above is read by a color imaging device, and the color tone of the read color tone is The identification symbol can be read by the printed circuit board identification symbol reading method configured to read the identification symbol based on the signal output, and (8) by the printed circuit board identification symbol recording method described in (1) to (5) above. It comprises a printed circuit board that has been formed and held, a means for transporting the printed circuit board to a predetermined mounting line, and a mounting means for recognizing the type of the transported printed circuit board and mounting and connecting a predetermined electronic component thereon. In a printed circuit board mounting apparatus, the identification symbol is read by a color imaging device as a means for recognizing the type of the printed circuit board, and the identification symbol is read based on the read color tone signal output. (9) Ceramic, Nox l! ! A circuit pattern made of a first layer on one main surface of the edge substrate, an alignment reference mark made of a plurality of self-conductors provided in the same process as the circuit pattern, and at least a dielectric mark formed sequentially on the top of the circuit pattern. each of the circuit forming patterns of the body, the resistor, and the cover glass, and each of the other alignment pattern marks provided in the same process as each of the circuit forming patterns in alignment with the area within any of the alignment reference marks. a printed circuit board comprising a printed circuit board, wherein the alignment reference mark is a digit display mark of a board identification symbol, and each of the other alignment pattern marks provided in accordance with the alignment reference mark is a pattern having a different color tone. (10) The above alignment reference marks and other positions of different color tones are provided by a thick film hybrid IC substrate having an identification symbol composed of the above and each color tone as identification information; The shape of the alignment pattern mark is made into a polygonal shape including a circle, and the color tone of the dielectric material is milky white.
By the thick film hybrid IC substrate according to (9) above, in which an identification symbol is recorded in which the color tone of the resistor is black and the color tone of the cover glass is green, and (11) the alignment reference mark. When the number of other alignment pattern marks with different color tones provided in the area is m and the types of color tones are 0, an identification symbol consisting of identification information expressed in an n-ary number of m digits is This is achieved by the thick film hybrid IC substrate described in (9) above, which is recorded.

(Function) According to the present invention, the alignment marks on the printed circuit board can also be used to record identification symbols, so there is no need to provide a special space for recording.Furthermore, it is not necessary to provide a special space for recording the paste of the printed circuit pattern on each layer. By appropriately selecting the position of the alignment mark and the color tone of each layer pattern, it is possible to record a large amount of identification information in the limited space of the alignment mark.

[Example] Hereinafter, an example of the present invention will be explained with reference to the drawings. Example 1゜ Fig. 1 is a plan view of a typical thick film hybrid IC. In this example, the electronic component 3 is attached to a ceramic substrate.

When manufacturing the printed circuit board 1, alignment marks 2 are usually provided to facilitate alignment of each layer pattern during printing.

FIG. 2 is an enlarged view of the alignment mark 2 in FIG.
It is also a plan view showing a method of recording an identification symbol on a printed circuit board according to the present invention. An embodiment of the present invention will be explained in comparison with the prior art with reference to FIG.

Conventionally, the rectangular pattern 4 of the first calendar conductor is printed on the printed circuit board 1 at the same time as the circuit pattern of the first calendar conductor, in accordance with the number of various pattern layers to be laminated thereafter, and when each pattern is formed, In this example, the alignment reference marks 2 are eight marks in two rows horizontally in the upper and lower rows indicated by 41 and 42), and above these, for example, in order from the left side of the lower row 42,
Circuit patterns were formed by overlapping and aligning the rectangular patterns of the dielectric layer, resistor layer, and cover glass layer. For this reason, in a general printed circuit board 1 that requires a circuit configuration by laminating 6 to 7 layers of patterns, the rectangular pattern 4 of the first conductor has only the number of laminated layers of each pattern constituting the circuit, as described above. In this example, 6 to 7 are required, and a large space is required for alignment.

The present invention is a method for recording an identification symbol on a printed circuit board by using the space of the alignment mark 2, and the principle thereof will be explained below.

In FIG. 2, a total of 8 rectangular patterns 4 of the first calendar conductor are formed, 4 each in the upper and lower tiers, and on top of these, a dielectric rectangular pattern 5 (milky white) and a resistor rectangular pattern 5 are formed. 6 (black) and a rectangular pattern 7 (green) of the cover glass are superimposed on each other with each color tone and position having the meaning of identification information.

FIG. 3 shows an example of the correspondence between the color tone of the rectangular patterns of each layer and the number of displays. In the second example, the milky white dielectric square pattern 5 corresponds to the display number 1, the black resistor square pattern 6 corresponds to the display number 2, and the green cover glass square pattern 7 corresponds to the display number 3. In this example, it is possible to record numbers from ○ to 3 on the rectangular Battersea 1 of one first calendar conductor.

FIG. 4 shows an example of recording numbers. This figure shows an example of a method for recording more complex identification information based on the correspondence example in FIG. 3, taking into account not only the color tone of each layer but also the arrangement thereof. In the example shown in FIG. 3, it was possible to record four numbers from O to 3 by superimposing another layer on the rectangular pattern 4 of one first calendar conductor, but the fourth In the figure, the 1st W! Combine the upper and lower two conductor rectangular patterns 4 to form a 2-digit 4
It is shown that a 1-digit decimal number can be expressed by recording the base number, and that it is possible to display a 4-digit decimal number by using a total of eight square patterns 4 of the first calendar conductors.

In Figure 4, a 2-digit quaternary number can be recorded by combining 2 vertical patterns out of 8 rectangular patterns.
Each of them corresponds to each digit of a four-digit decimal number. A milky-white dielectric material 5 (
By arranging the display number 1) and recording the quaternary value 01, the decimal value 1 can be displayed. Similarly, by placing a black resistor 6 (display number 2) on the first calendar conductor corresponding to the first digit of the quaternary number and recording the quaternary value 02, the decimal value 2
can be displayed. Similarly, the first digit corresponding to the first digit of the quaternary number
! By placing a green cover glass 7 (display number 3) on the F conductor and recording a quaternary value 03, a decimal value 3 can be displayed. If a milky white dielectric is placed on the first prefectural body corresponding to the second digit of the quaternary number, a quaternary value of 10 can be recorded, and a decimal value of 4 (=IX4m+OX4°) will be displayed.

Next, the decimal value 7092 shown in the third row from the bottom of Figure 4
This will be explained in more detail using an example where . 10
By placing a milky-white dielectric on the top of the two rectangular patterns in the first column from the left, which corresponds to the fourth digit of the decimal number, and a green cover glass on the bottom, a quaternary value of 13 is recorded, and a decimal value of 13 is recorded. 7 (=1x4'+3x4°) was expressed. The second column from the left, which corresponds to the third digit of the decimal number, is only the first layer warm body, and in this case, the quaternary value OO is recorded.

Expresses the decimal value 0 ("0X41+OX4°).

By placing a black resistor in the upper row of the two rectangular patterns in the third column from the left, which corresponds to the second digit of the decimal number, and a milky-white dielectric material in the lower row, a quaternary value of 21 is recorded. The value 9 (=2X41+IX4°) was expressed. The two square patterns in the rightmost column corresponding to the first decimal digit are:
Arrange a black resistor only in the lower row and record the quaternary value 02,
The decimal value 2 (=OX41+2X4°) is expressed. As a result, the numerical value 7092 could be recorded as identification information.

Other numerical values can be recorded in a similar manner, and in the case of the example shown in FIG. 4, numerical values from oooo to 9999 can be recorded as identification information.

According to this embodiment, identification symbols can be recorded on alignment marks that were conventionally used only for alignment, so it is possible to record identification symbols with a large amount of identification information in a small space on a printed circuit board. Example 2゜Example] In this example, a total of 8 rectangular patterns 4 of first layer warm bodies are used.
was used to display a 4-digit] O-adic number, but if you want to record even more identification information, you can change the number of rectangular patterns on the first layer warm body to 8 as in Example 1, and change the color tone of each layer. If the number of species is increased by one, from 3 to 4, 4” = 6553
Six types of identification information can be recorded. Generally, when the number of rectangular patterns in the first layer conductor is m and the number of color tones in each layer pattern is D, the identification information can be expressed as an m-digit n-ary number, and in this case, there are n ln types of identification information. Recording is possible. According to this embodiment, it is possible to display identification information as an n-ary number of m digits.

Example 3 Although the shape of the alignment mark explained in Example 1 was rectangular for both the first layer layer 4 and each layer pattern, it is also possible to make it circular in this example. By making the shape circular, there are no corners compared to a rectangular shape, so printing performance during pattern formation is improved, and an identification symbol containing a large amount of identification information can be more accurately recorded in a smaller space.

The shape of the identification mark that also serves as an alignment mark may be a polygon such as a triangle, a square, a hexagon, or a hexagon.

Embodiment 4 As shown in FIG. 5, part or all of the alignment mark on which the identification symbol described in Embodiment 1 is recorded can be removed by laser beam irradiation. In FIG. 5, a recording change is performed by irradiating the rectangular pattern 5 of the resistor with a laser beam to form a removed portion 9. According to this embodiment, - The originally recorded identification information can be easily changed.

Further, if this recording change is performed in the resistance value adjustment step of the resistor pattern by laser trimming, there is no need to provide a new recording change step, which is economical.

Example 5゜The shape of the first layer warm body of the alignment mark 4 explained in Example 1 was rectangular, but in this example, it can also be made into an annular shape, as shown in FIG. . In FIG. 6, a dielectric rectangular pattern 5, a resistor rectangular pattern 6, and a cover glass rectangular pattern of each tone are fitted in the center of the annular first layer conductor 8 in correspondence with the identification information. The dielectric, resistor, and cover glass were arranged so that the base of each rectangular pattern was directly on the substrate surface.

According to this embodiment, when recording is changed by laser beam irradiation as described in the fourth embodiment, since the base of the portion removed by the laser is directly on the substrate surface, the changed location can be easily identified.

Example 6゜First prefectural body 4 where the identification symbol explained in Example 1 can be recorded
, a dielectric 5, a resistor 6, and a cover glass 7 in a rectangular pattern on a mask for thick film printing.

According to this embodiment, it is possible to manufacture a thick film hybrid ■C on which an identification symbol is recorded.

Example 7゜The position and color tone of the rectangular pattern on each layer in which the identification symbol described in Example 1 was recorded was read by a television camera,
This data was sent to a computer and processed by the computer which had previously stored the symbolization rules shown in FIGS. 3 and 4 to identify the recorded symbols. According to this embodiment, an identification symbol containing a large amount of information can be easily read.

Example 8 This example will be explained with reference to FIG. A color television camera 10 that scans the alignment mark 2 recording the identification symbol according to Example 1 formed on the printed circuit board 1 to read its position and color tone, and a computer 11 connected thereto are provided. As explained in Example 7, the computer 11 had previously stored the symbolization rules explained in FIGS. 3 and 4. According to this embodiment, an identification symbol that records a large amount of information can be easily read.

Example 9 As explained in FIG. 3 in Example 1, the resistor was of one color, black. Usually, in thick film printed circuit boards, there are 3 to 4 resistors.
Since resistor pastes with different sheet resistance values are used, a coloring agent is added to use resistor pastes with different colors for each sheet resistance value. According to this example,
The symbolization rule in Example 1 was a quaternary number, but it is now a hexadecimal to hexadecimal number, so about 25 to 80 times more information than in the first embodiment can be recorded.

Example 10 Using the identification symbol recording method described in Example 1 and the printing mask described in Example 6, a thick film hybrid IC on which one product name was recorded was manufactured. According to this embodiment, since the manufacturing conditions can be automatically changed by identifying the product name, the manufacturing equipment can be unmanned in the process after soft assembly of the thick film hybrid IC component.

[Effects of the Invention] As detailed above, the present invention has the following effects.

(1) Since complex identification information can be recorded on the alignment mark on the printed circuit board, a large amount of identification information can be recorded in a small space.

(2) The number of alignment marks in the printed circuit board is m, the color tone of each layer pattern is n types, and the identification information is 1 digit nXI
! Since it can be expressed numerically, n''' types of identification information can be recorded.

(3) By making the shape of each recording pattern a polygon such as a circle or a rectangle, printability during pattern formation is improved, and identification symbols with a large amount of identification information can be printed in a smaller space. Can record accurately.

(4) Since part or all of the recorded pattern can be removed by laser beam irradiation, the recorded identification information can be easily changed.

(5) By fitting each of the other N recording patterns into the annular positioning mark of the first prefectural body, the base of the area removed by the laser beam becomes directly on the substrate surface, making it easy to change the recording location. can be determined.

(6) Since the identification symbol recording pattern is provided on the circuit pattern printing mask, a thick film hybrid C can be manufactured in which a large amount of identification information is recorded.

(7) Color imaging device: Since identification symbols can be read more easily, recorded symbols can be easily identified.

(8) In the method of recording identification symbols, for example, the number of discolorations on the resistor can be easily increased, so that a larger amount of information can be recorded.

In other words, it is easy to adjust the color tone by including not only the body color but also a suitable pigment in the printing paste.

(9) By recording symbols that can identify the product name etc. on the thick film hybrid IC, different manufacturing conditions can be automatically set for each type of board when mounting electronic components, so that manufacturing equipment can be unmanned.

[Brief explanation of drawings]

Fig. 1 is a plan view of a typical thick film hybrid IC, Fig. 2 is a plan view of an identification symbol according to an embodiment of the present invention, Fig. 3 is an example of a correspondence table between color tone and display number, and Fig. 4 is a plan view of a typical thick film hybrid IC. A table of numerical recording examples, FIG. 5 is a plan view of an identification symbol showing an example of changing the recording mark after laser beam irradiation, and FIG. 6 is a different example in which the positioning mark is shaped like a door. FIG. 7 is a schematic diagram showing an identification symbol reading device. <Explanation of symbols> 1...Printed circuit board 2 Alignment mark 3...
・Electronic component 4... Rectangular pattern of first prefectural body 5 Rectangular pattern of dielectric material 6... Rectangular pattern of resistor 7... Rectangular pattern of cover glass 8... Annular first prefectural body 9. Laser Removal unit 10 Color TV camera 11/calculator

Claims (11)

[Claims] 1. An alignment reference mark made of a plurality of said conductors is provided on one main surface of an insulating substrate in the same process as the formation of a circuit pattern made of a first layer conductor, and at least a dielectric material, a resistor material and a cover glass are provided thereon in sequence. and other alignment pattern marks provided in accordance with any of the alignment reference marks in the same process as the formation of each pattern, and the alignment reference marks are used to identify the substrate. The digit display mark of the symbol and each of the other alignment pattern marks provided in accordance with the alignment reference mark are composed of patterns with different color tones, and each color tone is used as identification information. A method for recording an identification symbol on a printed circuit board, comprising recording an identification symbol using a reference mark and other positioning pattern marks of different colors provided within the reference mark. 2. The alignment reference mark and each of the other alignment pattern marks having different tones are formed into a polygonal shape including a circle, the dielectric has a milky white color, the resistor has a black tone, and the cover glass has a color tone. 2. The method for recording an identification symbol on a printed circuit board according to claim 1, wherein the symbol is green. 3. When the number of other alignment pattern marks with different color tones provided in the area of the alignment reference mark is m, and the types of color tones are n, the identification information is displayed in an n-ary number of m digits. 3. A method for recording an identification symbol on a printed circuit board according to claim 1 or 2. 4. Laser light is selectively irradiated onto at least one of the alignment pattern marks provided in the area of the alignment reference mark and which has a different color tone to remove part or all of the alignment pattern mark, thereby removing the identification information. 4. A method for recording an identification symbol of a printed circuit board according to claim 1, wherein the identification symbol recording method is configured to additionally record an identification symbol. 5. 4. Printing according to claim 1, wherein the alignment reference mark has an annular shape, and each of the other alignment pattern marks having different colors is fitted into the center of the annular shape of the reference mark. Method for recording board identification symbols. 6. An alignment reference mark made of a plurality of said conductors is provided on one main surface of an insulating substrate at the same time as the formation of a circuit pattern made of a first layer conductor, and at least a dielectric material, a resistor material and a cover glass are sequentially placed thereon. As a mask for printing and forming a circuit pattern used in manufacturing a printed circuit board having each of the other alignment pattern marks provided in alignment with any of the alignment reference marks at the same time as pattern formation, the above-mentioned A printing mask comprising either an alignment reference mark or other alignment pattern marks formed in advance on the circuit pattern printing mask. 7. The identification symbol of the printed circuit board on which the identification symbol is formed and held by the printed circuit board identification symbol recording method according to any one of claims 1 to 5 is read by a color imaging device, and the identification symbol is recorded based on the read color tone signal output. A method for reading identification symbols on printed circuit boards. 8. A printed circuit board on which an identification symbol is formed and retained by the printed circuit board identification symbol recording method according to any one of claims 1 to 5, means for transporting the printed circuit board to a predetermined mounting line, and recognition of the type of the transported printed circuit board. In the printed circuit board mounting apparatus, the identification symbol is read by a color imaging device as means for recognizing the type of the printed circuit board. A printed circuit board mounting apparatus comprising printed circuit board identification symbol reading means configured to read the identification symbol based on a color tone signal output. 9. A circuit pattern made of a first-layer conductor on one main surface of a ceramic insulating substrate, an alignment reference mark made of a plurality of conductors provided in the same process as the circuit pattern, and at least a dielectric material sequentially formed thereon. , each of the circuit forming patterns of the resistor and the cover glass, and each of the other alignment pattern marks provided in the same process as each of the circuit forming patterns in alignment with the area within any of the alignment reference marks. The alignment reference mark is a digit display mark of a board identification symbol, and each of the other alignment pattern marks provided in accordance with the alignment reference mark is a pattern with a different color tone. 1. A thick film hybrid IC substrate having an identification symbol composed of a plurality of colors and each color tone as identification information. 10. The alignment reference mark and each of the other alignment pattern marks having different tones are formed into a polygonal shape including a circle, the dielectric has a milky white color, the resistor has a black tone, and the cover glass has a color tone. 10. The thick film hybrid IC substrate according to claim 9, wherein an identification symbol in green is recorded thereon. 11. When the number of other alignment pattern marks with different color tones provided in the area of the alignment reference mark is m, and the types of color tones are n, the identification information is displayed in an n-ary number of m digits. 10. The thick film hybrid IC substrate according to claim 9, further comprising an identification symbol recorded thereon.