Field of the Invention
The present invention relates to a printing element substrate including a printing element which forms information such as a character or figure on a printing medium such as paper or cloth, a printhead including the printing element substrate, and a printhead manufacturing method.
Description of the Related Art
To meet a demand for a higher printing speed in inkjet printers, there has been proposed a line head configured by arranging a plurality of printing element substrates in a predetermined direction at the same width as the width (to be referred to as printing width) of a printing medium. This printhead is fixed and can print simultaneously at the printing width, achieving higher-speed printing than by a serial printer which prints by reciprocating the printhead. Japanese Patent Laid-Open No. 2007-296638 (to be referred to as a literature) discloses an example of the structure of the line head.
Referring to
The line head type printhead can print on a wider printing medium by increasing the number of printing element substrates arranged along the printing width. However, as the number of printing element substrates increases, the number of input terminals of the line head also increases. Also when implementing higher-resolution printing of photographic quality by the line head, it is effective to increase the printing element density with respect to the printing width on the printing element substrate or increase the number of printing element arrays along the printing width. In this case, the number of printing elements per printing element substrate increases. A larger number of printing elements leads to a larger number of data to be input to the printing element substrate. To cope with a larger number of data without decreasing the printing speed, the data transfer speed needs to be increased. When the wiring from the head input terminal to the printing element substrate becomes long, like the line head, the waveform may deteriorate midway along the wiring or data may be garbled by external noise entering the wiring. This makes high-speed data transfer difficult.
To solve this problem, a low voltage differential signaling (LVDS) scheme is effective.
As shown in
When impedances on the data transmission line and the terminating resistance element at the receiving end match each other, the data transfer waveform becomes a waveform as shown in
However, it is difficult to mount a component such as the resistive element near the end of the printing element substrate of the printhead in terms of reliability and maintenance due to requests for insulation of the resistive element from ink and flatness of the head surface when wiping ink from the head surface. As the terminating resistance element, a printing element formed on a printing element substrate by a semiconductor process may be used. Such a printing element substrate is manufactured using a semiconductor manufacturing process, and many printing element substrates are fabricated at once from one silicon wafer. Printing element substrates obtained by the semiconductor manufacturing process vary in the resistance of the resistive element by 20 to 30% under the influence of manufacturing variations. Therefore, even if the resistive element is arranged, some printing element substrates may generate an impedance mismatch to distort the data transfer waveform, failing high-speed data transfer again.
To reduce such manufacturing variations, there is known a method of trimming a resistive element by a laser or the like to adjust the resistance to a predetermined value. However, this method raises the manufacturing cost. In addition, if the laser damages the substrate surface, insulation of the resistive element from ink may be impaired, resulting in poor reliability.
The present invention provides a high-reliability printing element substrate, printhead, and printhead manufacturing method capable of suppressing deterioration of the transmission waveform caused by an impedance mismatch and transferring data quickly without using an external terminating resistance element.
According to a first aspect of the present invention there is provided a printhead manufacturing method comprising the steps of: preparing a printing element substrate including a receiver including a first terminal and second terminal which receive a first signal and second signal of differential signals, respectively, a first input pad which is connected to the first terminal and externally receives the first signal, a second input pad which is connected to the second terminal and externally receives the second signal, and a plurality of selection pads which are connected to the second terminal via at least two resistive elements out of a plurality of printing elements to obtain combined resistances different from each other; preparing a head substrate including a first transmission line which transmits the first signal, and a second transmission line which transmits the second signal; selecting one of the plurality of selection pads to be connected to the first transmission line in accordance with values of the combined resistances; and connecting at least one of the plurality of selection pads selected in the selection step and the first transmission line, connecting the first input pad and the first transmission line, and connecting the second input pad and the second transmission line.
According to a second aspect of the present invention there is provided a printing element substrate comprising: a receiver including a first terminal and second terminal which receive a first signal and second signal of differential signals, respectively; a first input pad which is connected to the first terminal and externally receives the first signal; a second input pad which is connected to the second terminal and externally receives the second signal; and a variable resistance section which is arranged to adjust a resistance between the first terminal and the second terminal, and includes a plurality of selection pads which are connected to the second terminal via at least two resistive elements out of a plurality of printing elements, wherein when the first signal is externally input to at least one of the plurality of selection pads and the first input pad and the second signal is input to the second input pad, a combined resistance by the plurality of resistive elements is set between the first terminal and the second terminal.
According to a third aspect of the present invention there is provided a printhead comprising: the above described printing element substrate; and a head substrate including a first transmission line which is connected to a first input pad and transmits a first signal to the first input pad, and a second transmission line which is connected to a second input pad and transmits a second signal to the second input pad, wherein at least one selection pad out of a plurality of selection pads is connected to the first transmission line.
Further features of the present invention will be apparent from the following description of exemplary embodiments (with reference to the attached drawings).
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the description, serve to explain the principles of the invention.
An exemplary embodiment(s) of the present invention will now be described in detail with reference to the drawings. It should be noted that the relative arrangement of the components, the numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless it is specifically stated otherwise.
The arrangement of a printhead according to the first embodiment will be described.
As shown in
As shown in
The input pad 1051 corresponds to the first input pad, and the input pad 1054 corresponds to the second input pad. The input pad 1052 corresponds to the third input pad, and the input pad 1053 corresponds to the fourth input pad. The resistive element 102 corresponds to the first resistive element, the resistive element 103 corresponds to the second resistive element, and the resistive element 104 corresponds to the third resistive element.
One terminal (to be referred to as a positive input terminal) out of the two differential input terminals of the LVDS receiver 101 is connected to the input pad 1051. The other terminal (to be referred to as a negative input terminal) is connected to the input pad 1054. Of differential signals, a signal input to the positive input terminal will be referred to as the first signal, and a signal input to the negative input terminal will be referred to as the second signal. The positive input terminal corresponds to the first terminal, and the negative input terminal corresponds to the second terminal.
One of the two terminals of the resistive element 102 is connected to the negative input terminal out of the two differential input terminals of the LVDS receiver 101. The other one of the two terminals of the resistive element 102 is connected to the resistive elements 103 and 104. One of the two terminals of the resistive element 103 is connected to the resistive elements 102 and 104, and the other terminal is connected to the input pad 1052. One of the two terminals of the resistive element 104 is connected to the resistive elements 102 and 103, and the other terminal is connected to the input pad 1053.
The printing element substrate 100 is fabricated by a semiconductor manufacturing process. A plurality of printing element substrates 100 are formed at once on one silicon wafer and cut out to obtain the individual printing element substrates 100. The resistive elements 102, 103, and 104 of the printing element substrate 100 can be formed by patterning a material such as polysilicon by photolithography, or as diffused resistors in which boron, phosphorus, or the like is diffused in a silicon substrate via a mask formed at a desired position by photolithography. When printing element substrates are formed using such a semiconductor manufacturing process, the film thickness and width of the material vary between positions on the silicon wafer or manufacturing lots. Hence, the resistances of even the resistive elements 102, 103, and 104 vary by about 20 to 30% between the printing element substrates 100.
If the resistive elements arranged as terminating resistors have variations as large as about 20 to 30%, some printing element substrates may generate an impedance mismatch to distort the data transfer waveform, as shown in
The printing element substrate 100 is mounted on the supporting member 263 of the printhead 200 shown in
The pad portions 2021 to 2024 are terminals for electrically connecting to the printing element substrate 100 via wires 205 by wire bonding. The external connection terminals 2031 and 2032 are terminals for electrically connecting the pad portions 2021 to 2024 and the outside of the head substrate 201. The transmission lines 2041 and 2042 are a pair of wiring lines for transmitting differential signals externally input via the external connection terminals 2031 and 2032 to the LVDS receiver 101.
The transmission line 2042 is connected to the pad portion 2024 and external connection terminal 2032. The transmission line 2041 has one end commonly connected to the pad portions 2021 to 2023, and the other end connected to the external connection terminal 2031. The pad portion 2024 is connected via the wire 205 by wire bonding to the input pad 1054 connected to the negative input terminal of the LVDS receiver 101. The input pad 1051 connected to the positive input terminal of the LVDS receiver 101 is connected to the pad portion 2021 via the wire 205 by wire bonding. This arrangement is common to
The connection between the pad portions 2022 and 2023 and the printing element substrate 100 can be selected from connections shown in
In the arrangement shown in
In the arrangement shown in
In the arrangement shown in
RB=R1+R2
In the arrangement shown in
RC=R1+R3
That is, the three resistances RA, RB, and RC can be used as the resistances of the terminating resistors by selecting three connection configurations as shown in
In the arrangement shown in
The three resistive elements 102 to 104 of the printing element substrate are fabricated by a semiconductor process. Thus, the resistances R1, R2, and R3 of resistive elements on many printing element substrates vary by 20 to 30%.
However, the resistive elements 102 to 104 on one printing element substrate are manufactured at once and are close to each other on the silicon wafer. The relative ratio of the resistances R1, R2, and R3 of resistive elements on a single substrate is almost constant. Hence, the magnitude ratio of the combined resistances RA, RB, and RC of a plurality of resistive elements fabricated on a single substrate is also almost constant against manufacturing variations.
More specifically, a plurality of resistances are set for one printing element substrate, and pad portions to be connected are selected in accordance with the finish of the printing element substrate. Resistance variations of the terminating resistor when connecting a wiring board can be made smaller than variations of 20 to 30% in the resistances R1, R2, and R3 arising from manufacturing variations.
A case in which R1, R2, and R3 are set to increase the combined resistance in order of RA, RB, and RC and the design target of the combined resistance RB is set to 100Ω will be explained with reference to
When the resistances of the resistive elements of a selected printing element substrate are close to the design values, the combined resistance RB becomes almost 100Ω, and thus connection is selected so the combined resistance RB shown in
A case in which the resistances R1, R2, and R3 of the printing element substrate vary to be smaller than the design values owing to manufacturing variations will be examined. For example, when the combined resistance RB becomes almost 80Ω, the combined resistances RA and RC also vary to be smaller than the design values in correlation with the combined resistance RB, and connection is selected so the combined resistance RC becomes a terminating resistance. That is, the connection configuration as in
A case in which the resistances R1, R2, and R3 of the printing element substrate vary to be larger than the design values owing to manufacturing variations will be considered. For example, when the combined resistance RB becomes almost 120Ω, the combined resistances RA and RC also vary to be larger than the design values in correlation with the combined resistance RB, and connection is therefore selected so the combined resistance RA becomes a terminating resistance. That is, the connection as in
In this manner, one of the connection states in
A printhead manufacturing method according to the first embodiment will be explained.
Upon completion of a process of manufacturing a wafer including a plurality of printing element substrate chips, wafer inspection is performed for chip non-defective determination (step 701). At this time, a plurality of combined resistances based on combinations of two or more resistive elements out of a plurality of resistive elements arranged in the variable resistance section of the printing element substrate are measured. The combined resistance can be measured by bringing a measurement terminal into contact with the input pads 1052 to 1054 shown in
After the wafer is cut into a plurality of chips (step 704), a non-defective chip is mounted on the supporting member of a printhead (step 705). The mounted chip and the terminating resistance information obtained by wafer inspection are collated (step 706). One of the connection patterns shown in
In the above-described way, variations in the resistance of the terminating resistance element connected between the two input terminals of the receiver of each chip can be corrected.
The printing element substrate according to the embodiment includes a plurality of resistive elements at the input portion of the printing element substrate, and a plurality of pads connected to one of the two input terminals of the receiver using the combined resistance of two or more resistive elements as a terminating resistance. Pads are connected so that a target terminating resistance is set between the two input terminals of the receiver. The embodiment can obtain an effect of correcting variations in the resistance of the terminating resistance element owing to manufacturing variations in a semiconductor process. As a result, deterioration of the transmission waveform caused by an impedance mismatch can be suppressed, and data can be transferred quickly without raising the manufacturing cost of the printing element substrate and impairing the reliability of the printhead.
The arrangement of the pad portions of a receiver including resistive elements of the resistances R1, R2, and R3 on the printing element substrate will be described in detail.
As shown in
The print data supply circuit 208 includes a shift register 282 and latch circuit 281. The block selection circuit 207 includes a circuit 271 including a shift register and latch, and a decoder 272. Each printing element driving circuit 240 includes a printing element 202 and a power transistor 203 which controls a current to be supplied to the printing element 202. The heat generation circuit 209 is formed from, for example, a counter. In
The operation of the printing element substrate shown in
The LVDS receiver 101a converts differential signals of the CLK signal into a single-end signal and supplies it to the print data supply circuit 208 and block selection circuit 207. The LVDS receiver 101b converts differential signals of the DATA signal into a single-end signal and supplies it to the print data supply circuit 208. The LVDS receiver 101c converts differential signals of the CLKHE signal into a single-end signal and supplies it to the heat generation circuit 209. An LT signal is input to the block selection circuit 207, print data supply circuit 208, and heat generation circuit 209.
In the print data supply circuit 208, the shift register 282 receives the DATA signal synchronized with the CLK signal. The latch circuit 281 receives each bit signal of the shift register 282, latches it in accordance with the LT signal, and outputs it to a corresponding AND circuit 204. This signal is a print data signal 206 shown in
The heat generation circuit 209 receives a serial output from the shift register 282 and the LT signal. Upon receiving the CLKHE signal from the LVDS receiver 101c, the heat generation circuit 209 latches serial data from the shift register in accordance with the LT signal. The heat generation circuit counts the number of pulses of the CLKHE signal based on the latched data, and generates a heat pulse as a signal indicating the timing to drive the printing element.
Each AND circuit 204 ANDs the heat pulse, block selection signal 210, and print data signal 206, and outputs the result to a corresponding printing element driving circuit 240. The power transistor 203 is turned on in response to the signal input from the AND circuit 204 to the printing element driving circuit 240. Then, a current flows through the printing element 202.
Each of the DATA signal, CLK signal, and CLKHE signal is input as differential signals to the printing element substrate 100. However,
The DATA signal is input to the shift register 282 at a timing between the leading and trailing edges of the CLK signal. Based on the heat pulse information of the DATA signal, the heat generation circuit 209 counts the number of pulses of the CLKHE signal, and generates a heat pulse (HE signal). To represent execution of one printing operation,
Note that
As shown in
The head connection terminals CLK and CLKHE are commonly connected to the printing element substrates KD1 to KDn. The respective head connection terminals DATA1 to DATAn are connected to the corresponding printing element substrates KD1 to KDn.
On the printing element substrate KDn, terminating resistance elements are connected between transmission lines for inputting differential signals to the LVDS receivers 101a and 101c. In contrast, on the printing element substrates KD1 and KD2, no terminating resistance element is connected between transmission lines for inputting differential signals to the LVDS receivers 101a and 101c.
That is, one of the connection configurations in
Terminals which are connected to respective printing element substrates and receive differential signals, like the head connection terminals DATA1 to DATAn, are connected by selecting one of the connection states in
The arrangement of a printhead in the second embodiment will be described. Note that the second embodiment will explain a difference from the first embodiment in detail. A detailed description of the same arrangement as that in the first embodiment will not be repeated.
As shown in
The first embodiment has proposed different configurations of connection between the input pad of the printing element substrate 100 and the pad portion of the head substrate 201. In the first embodiment, the resistance is selected by switching the connection configuration. To the contrary, in the connection configuration of the second embodiment, the connection between the input pad and the pad portion is common, but the wiring connection pattern on the head substrate is different as shown in
The arrangement shown in
In the arrangement shown in
RB=R1+R2
In the arrangement shown in
RC=R1+R3
In the second embodiment, a plurality of types of head substrates are prepared by changing the configuration of connection between a plurality of pad portions and the transmission line 2041. By selecting one of the head substrates in accordance with the state of the printing element substrate, one of the combined resistances RA, RB, and RC can be selected as a terminating resistance. Even in the second embodiment, resistances connected between the transmission lines 2041 and 2042 become equal to those in the first embodiment. The second embodiment can therefore obtain an effect of correcting variations in terminating resistance, similar to the first embodiment.
In the arrangement shown in
A printhead manufacturing method according to the second embodiment will be explained.
Upon completion of a process of manufacturing a wafer including a plurality of printing element substrate chips, wafer inspection is performed for chip non-defective determination (step 901). At this time, a plurality of combined resistances based on combinations of two or more resistive elements out of a plurality of resistive elements arranged in the variable resistance section of the printing element substrate are measured. Information about a plurality of combined resistances will be called terminating resistance information. Then, the chip non-defective determination result and terminating resistance information are output (step 902). A description of the chip non-defective determination result will be omitted. The terminating resistance information obtained by the inspection is stored (step 903). At this time, chip information including an identifier different for each chip is stored together with the terminating resistance information.
After the wafer is cut into a plurality of chips (step 904), a non-defective chip is selected (step 905). Then, the selected chip and the terminating resistance information obtained by wafer inspection are collated (step 906). One of the head substrates shown in
In this fashion, variations in the resistance of the terminating resistance element connected between the two input terminals of the receiver of each chip can be corrected.
In the second embodiment, the head substrate needs to be changed in accordance with variations in terminating resistance. However, the connection by wire bonding need not be changed in accordance with variations in terminating resistance, avoiding complication of the wiring bonding process.
The third embodiment is directed at another example of the arrangement of the input portion on the printing element substrate. The third embodiment will explain a difference from the first embodiment in detail. A detailed description of the same arrangement as that in the first embodiment will not be repeated.
As shown in
One terminal of each of the resistive elements 602 and 603 is connected to the negative input terminal of the receiver 101. The other terminal of the resistive element 602 is connected to the input pad 1052, and the other terminal of the resistive element 603 is connected to the input pad 1053. One of the two terminals of the resistive element 601 is connected to the input pad 1052 and resistive element 602, and the other terminal is connected to the input pad 1053 and resistive element 603.
R1, R2, and R3 are the resistances of the resistive elements 601, 602, and 603, respectively. The connections shown in
Letting RAA be the combined resistance in the connection shown in
Letting RBB be the combined resistance in the connection shown in
Letting RCC be the combined resistance in the connection shown in
By setting the resistances R1, R2, and R3, the combined resistances RAA, RBB, and RCC can be set to arbitrary resistances. Similar to the first and second embodiments, even the third embodiment can obtain an effect of correcting manufacturing variations in terminating resistance.
In the third embodiment, the parallel connection of resistive elements is a basic arrangement, unlike the first embodiment. To obtain the same combined resistance as that described in the first embodiment, the resistances R1 to R3 become higher than those in the first embodiment. The terminating resistance used in the LVDS receiver is as relatively low as about 100Ω. In the first embodiment, the resistances R1 to R3 are equal to or lower than 100Ω because the series connection of resistive elements is a basic arrangement. For a resistive element generally formed by a semiconductor manufacturing process, even a small sheet resistance value is about several ten Ω/□. To obtain a resistance of 100Ω or less by one resistive element, the number of sheets for forming resistive elements decreases, the sheet widens, and the resistive element area increases for high-precision design.
In the third embodiment, the resistances R1 to R3 are higher and the number of sheets are larger, compared to the first embodiment. However, the resistances can be designed at higher precision without increasing the resistive element area. Note that the third embodiment may be applied to the second embodiment.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application Nos. 2010-290660 filed on Dec. 27, 2010 and 2011-269398 filed on Dec. 8, 2011, which are hereby incorporated by reference herein in their entirety.
Number | Date | Country | Kind |
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2011-269398 | Dec 2011 | JP | national |
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