JP4638191B2 - Thermal head inspection method - Google Patents

Description

  The present invention relates to a method for inspecting a thermal head incorporated in a printer mechanism.

  Conventionally, as shown in FIG. 4, a thermal head incorporated in a printer mechanism has a substrate 101 and a plurality of heating elements 103 arranged on one end side of the substrate 101. The individual electrode wiring 104 and the common electrode wiring 105 for generating heat are connected, and a plurality of driver ICs 107 for controlling the heat generation of the heat generating element 103 are arranged substantially parallel to the heat generating element 103 on the other end side of the substrate 101. The driver IC 107 has a structure in which a signal electrode wiring 106 for transmitting a signal from an external wiring board is connected.

  Further, as shown in FIG. 5, the individual electrode wiring 104, the common electrode wiring 105, and the signal electrode wiring 106 are electrically connected to the probe needle n of the inspection apparatus to conduct a thermal head characteristic inspection. A pad portion p to be used is provided.

  The pad portion p is composed of a base electrode layer p1 and an upper electrode layer p2. Usually, after the electrode wiring is formed in a predetermined pattern, the upper electrode is formed on the base electrode layer p1 which is a pad portion p formation region of the electrode wiring. An electrode layer p2 is formed.

In such a thermal head, a thermal recording medium such as thermal paper or an ink ribbon is slidably contacted on the heating resistor using a platen roller, and a number of heating resistors are individually selected based on print data from the outside. In addition, Joule heat is generated and the generated heat is conducted to the recording medium to form a predetermined print on the recording medium, thereby functioning as a thermal head.
JP 2001-102411 A

  By the way, the electrode wiring such as the individual electrode wiring 104, the common electrode wiring electrode 105, and the signal electrode wiring 106 described above is formed by sputtering or photolithography, and the surface state thereof is smooth.

  Further, when the upper electrode layer p2 is attached by electroless plating, the periphery of the pad portion p formation region of the electrode wiring is covered with a resist. Then, the upper electrode layer p2 is attached only to the pad portion forming region which is the opening of the resist. Since the surface of the base electrode layer p1 is smooth, the surface state of the upper electrode layer p2 is also smooth. For example, the surface reflectance of the upper electrode layer p2 is about 80%.

  Further, after the formation of the upper electrode layer p2, the resist is removed. At this time, when the resist is removed by immersing it in a stripping solution, the resist residue once stripped from the base electrode layer p1 may adhere to the upper electrode layer located in the vicinity. Residue resist film r exists on a part of the upper surface of ground electrode layer p2.

  The characteristic inspection of the thermal head having such a pad portion p is performed by placing the thermal head on the stage of the inspection apparatus and bringing the probe needle n of the inspection apparatus into contact with the pad portion p.

  However, when the resist film r is adhered on the pad portion as described above, the probe needle n of the inspection apparatus comes into contact with the resist film r, and in this state, it is electrically connected to the upper electrode layer p2. Cannot be achieved.

  Therefore, the upper electrode layer p2 is tried to come into contact with the probe needle n by increasing the pressing force of the probe needle n or by sliding the probe needle n laterally and scratching the surface of the pad portion p. Things were also done.

  However, even in this case, since the surface state of the pad portion p is smooth, the resist film r cannot be removed well because the probe needle n slides on the surface, etc. Existed.

  The present invention has been made in view of the above drawbacks, and an object of the present invention is to provide a method for inspecting the characteristics of a thermal head having a pad portion p in which measurement failure is unlikely to occur.

Inspection method for a thermal head according to the first embodiment of the present invention includes a substrate and a heat-generating elements arranged on the substrate, and an electrode wiring electrically connected to the heat generating element, a part of the electrode wiring In the area of
A thermal head inspection method for measuring and inspecting electrical characteristics of a thermal head having a formed pad portion and a resist film attached to the pad portion by bringing a probe needle into contact with the pad portion. to form a concavo-convex portion on the surface of, at the time of measurement and inspection, presses the probe needles on the pad portion by crushing the uneven portion, break through the resist film deposited on the surface of the uneven portion, the resist film to remove the, it is characterized in that the electrode wire and the measured electrical characteristics of the probe needle is energized test.
The thermal head inspection method according to the second aspect of the present invention includes a substrate, a heating element arranged on the substrate, an electrode wiring electrically connected to the heating element, and the electrode wiring. This is a thermal head inspection method for measuring and inspecting the electrical characteristics of a thermal head having a pad portion formed in a part of the region and a resist film attached to the pad portion by bringing a probe needle into contact with the pad portion. Forming an uneven portion on the surface of the pad portion, scratching the pad portion with the probe needle at the time of measurement inspection, and scraping the resist film attached to the surface of the uneven portion together with the uneven portion. The electrical characteristics are measured and inspected by energizing the electrode wiring and the probe needle.

The inspection method for a thermal head according to the first or second form of the present invention, the formation density of the uneven portion, one / 700 .mu.m ² above, I 30/700 .mu.m ² or less der Good .

According to the inspection method for a thermal head of the present invention, electrodes wire and the probe needles energized can be performed reliably, and can suppress the occurrence of test failures.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

  First, a thermal head to which the inspection method of the present invention is applied will be described. In this thermal head, a strip-like glaze layer 2 is formed on one long side of a long substrate 1, and a number of heating elements 3 are arranged on the glaze layer 2. A plurality of driver ICs 7 for controlling the heat generation of the heat generating element 2 are connected to the heat generating element 2 on the other long side of the substrate 1. The driver ICs 7 have a structure in which signal electrode wirings 6 for transmitting signals from the above-described individual electrode wirings 3 and external circuit wirings of an external wiring board (not shown) are connected to the driver ICs 7. The external wiring board is partially overlapped with the other long side of the substrate 1 described above, and the external wiring board and the substrate 1 are mechanically joined in this overlapping region.

  The substrate 1 which is the base of the thermal head is formed in a rectangular shape by various materials such as an insulating material such as alumina ceramics and single crystal silicon having an oxide film attached to the surface.

  Then, on the upper surface of the substrate 1, it functions as a support base material that supports the belt-like glaze layer 2, the heating element 3, the various electrode wirings 4, 5, 6 and the driver IC 7.

  When the substrate 1 is made of alumina ceramics, for example, an appropriate organic solvent or solvent is added to and mixed with ceramic raw material powders such as alumina, silica, and magnesia to form a slurry, and this is made into a conventionally known doctor. A ceramic green sheet is obtained by adopting a blade method, a calender roll method, or the like, and thereafter, the green sheet is punched into a predetermined shape and then fired at a high temperature (about 1600 ° C.).

  A glaze layer 2 extending in a strip shape in the longitudinal direction is formed on one long side of the upper surface of the substrate 1.

  This glaze layer 2 has the effect | action which accumulates the heat | fever which the heat generating element 3 emits inside, and maintains the thermal responsiveness of a thermal head favorably.

  When such a glaze layer 2 is made of glass, for example, a glass paste obtained by adding and mixing an appropriate organic solvent, organic binder, etc. to glass powder is applied to the upper surface of the substrate 1 by a conventionally known screen printing method or the like. It is formed by applying to a predetermined region and processing it into a predetermined shape by employing a conventionally known photolithography technique and etching technique, and then heating it at a high temperature of 850 ° C. to 950 ° C. for a predetermined time. .

  A plurality of heating elements 3 are formed on the belt-like glaze layer 2 described above.

  The heating elements 3 are linearly deposited and arranged at a density of 200 dpi (dot per inch) or 300 dpi. It consists of a resistor layer made of a resistive material.

  The individual electrode wiring 4 is connected to one end side of the heat generating element 3 and the common electrode wiring 5 is connected to the other end side in common, and a predetermined current is passed from the electrode wiring to the heat generating element 3 to thereby generate the heat generating element. 3 generates heat at a predetermined temperature.

  The individual electrode wiring 4 made of a metal material such as aluminum or copper connected to one end of each of the heating elements 3 is extended from one end side of the heating element 3 to the other end side of the upper surface of the substrate 1. . The other end is connected to the output terminal of the driver IC 7 and functions as a wiring for supplying power from the driver IC 7 to the heating element 3.

  Further, the common electrode wiring 5 made of a metal material such as aluminum or copper and having one end commonly connected to the heat generating element 3 is arranged on the upper surface of the substrate 1 and the outer periphery of the region where the individual electrode wiring 4 is formed on the other end side of the substrate 1 The other end is connected to the external circuit wiring of the external wiring board and functions as a power supply wiring for supplying power to the heating element 3. A voltage of about 24 V is normally applied to the heating element 3 by the common electrode wiring 5.

  Further, the signal electrode wiring 6 is disposed on the substrate 1 so as to extend from the mounting area of the driver IC 7 to the end of the substrate 1. The signal electrode wiring 6 has one end connected to the input terminal of the driver IC 7 and the other end connected to an external circuit wiring on the external wiring board. The signal electrode wiring 6 serves to supply a clock signal, an image data signal, a latch signal, a strobe signal, and the like from the printer to the driver IC 7.

  These heating elements 3, individual electrode wirings 4, common electrode wirings 5, and signal electrode wirings 6 have rough surface states by adopting conventionally known thin film forming techniques such as sputtering, photolithography techniques, etching techniques, and the like. It is formed to become.

  Further, a pad portion p is provided in a predetermined region of the individual electrode wiring 4 and the signal electrode wiring 6, and the pad portion p is connected to the output terminal and the input terminal of the driver IC 7 via the solder bump B. The pad portion p is formed by a base electrode layer p1 which is a predetermined region of these electrode wirings and an upper electrode layer p2 formed on the base electrode layer p1.

  The upper electrode layer p2 of the pad portion p is formed as follows.

  First, after the individual electrode wiring 4, the common electrode wiring 5, and the signal electrode wiring 6 are formed, a resist is applied over the entire area on these electrode wirings.

  Thereafter, an opening is provided in the resist corresponding to a region where the pad portion p on the electrode wiring is formed, and a part of the electrode wiring is exposed from this opening.

  Then, electroless plating is performed by immersing the substrate 1 in a plating solution. As a result, an upper electrode layer p2 made of, for example, nickel (Ni) is formed in the opening region of the resist.

  Thereafter, the resist is removed from the entire substrate 1. This removal is performed by dipping in a stripping solution. At this time, a part of the resist stripped from the substrate 1 may adhere to the above-described upper electrode layer p2. For this reason, the resist film r exists over the upper electrode layer p2. Such a resist film r is very thin, and the height of the uneven portion t described later is 0.5 μm or more, whereas its thickness is 0.1 μm or less.

  By the way, the upper electrode layer p2 formed in this way has an uneven portion t on its surface. The above-described resist film r is also adhered on the uneven portion t. The uneven portion t reflects the surface state of a predetermined region of the individual electrode wiring 4 and the signal electrode wiring 6 as the base electrode layer p1 as it is. In this embodiment, the uneven portion t is defined as including one convex portion between the valleys.

The unevenness t has a formation density of 1 piece / 700 μm ² or more and 30 pieces / 700 μm ² or less, and each uneven part t has a hemispherical shape with a diameter of 0.5 μm to ³ μm. In addition, the surface reflectance of the pad part p corresponding to the formation density of the uneven part t was 30% to 60%.

  Note that a driver IC 7 on which solder bumps B are formed is mounted on the upper electrode layer p2 after measurement and inspection of electrical characteristics is completed.

  On the other hand, a protective film 9 is deposited on the upper surfaces of the individual electrode wiring 4 and the common electrode wiring 5 except for the vicinity of the heating element 3 and driver IC 7 described above.

  This protective film 9 is for protecting the heating element 3, the individual electrode wiring 4 and the common electrode wiring 5 from corrosion caused by moisture contained in the atmosphere or wear due to sliding contact of the recording medium. It is formed to a thickness of 3 μm to 10 μm with a SiN-based, SiO-based, SiON-based inorganic material or glass.

  The protective film 9 is formed by a conventionally known thin film forming technique (sputtering method, vapor deposition method, CVD method, etc.) or thick film forming technique (screen printing method, dispenser method, etc.).

  A plurality of driver ICs 7 for controlling energization to the heat generating element 3 are arranged on the upper surface of the substrate 1. The driver IC 7 is arranged on the other end side of the substrate 1 so as to be substantially parallel to the heat generating element 3, and is arranged with a predetermined interval between the adjacent driver ICs 7.

  The individual electrode wiring 4 is connected to the output terminal of the driver IC 7 and the signal electrode wiring 6 is flip-chip connected to the input terminal at the pad portion p.

  The driver IC 7 for the thermal head has an integrated circuit in which a shift register, a latch, a switching element, an input terminal, an output terminal, and the like are integrated on one main surface of the silicon substrate at a high density. Are electrically connected through the individual electrode wiring 4.

  The driver IC 7 stores the image data in the shift register through the signal electrode wiring 6 and the input terminal of the driver IC 7 while synchronizing with the clock signal, and then stores the stored image data in the latch at the timing of the latch signal. While the strobe signal is input to the switching element, the heating element 3 is energized based on the image data in the latch.

  Further, the driver IC 7 is sealed with a sealing resin 8 made of a resin material such as a thermosetting epoxy resin.

  The sealing resin 8 is formed such that its cross-sectional shape forms a mountain shape, and functions to protect each wiring and driver IC 7 from corrosion due to moisture contained in the atmosphere.

  The sealing resin 8 is formed by, for example, applying a predetermined liquid precursor made of an epoxy resin so as to cover the driver IC 7 on the substrate 1 and heating and polymerizing the same at 130 ° C. to 150 ° C. The

  Here, the inspection method for the thermal head H of the present invention will be described.

  This characteristic inspection is for inspecting opening / closing of a circuit constituted by the pad portion p and the common electrode wiring 5, resistance value variations of the heating element 3, and the like. This inspection is performed after the upper electrode layer p2 is formed on the lower electrode layer p1 and before the driver IC 7 is mounted.

  (1) First, the thermal head H is placed on the stage, and one probe needle n is placed on the upper electrode layer p2 and the other probe needle n 'is placed on the common electrode wiring 5.

  (2) Next, with the probe needle n fixed, the stage s is gradually brought closer to the probe needle n and brought into contact with the upper electrode layer p2.

  (3) Thereafter, the probe needle n is pressed in the depth direction of the upper electrode layer p2.

  At this time, a large number of uneven portions t existing on the upper surface of the upper electrode layer p2 are crushed by the pressing force, and the resist film r existing on the uneven portions t is pierced, and as a result, adheres to the surface of the uneven portions. Since the resist film is removed and the material of the upper electrode layer p2 is exposed on the surface, the upper electrode layer p2 and the probe needle n can be energized.

  Since at least one uneven portion t exists in the contact surface between the probe needle n and the pad portion p when the probe needle n for characteristic inspection is pressed against the pad portion p, the uneven portion t As in the case where the probe needle n cannot pierce the resist film r on the upper surface of the pad portion p having no defect, it is possible to suppress the occurrence of inspection defects.

In this example, the base electrode layer was created under the following conditions.

· ^{O 2} content in the sputtering gas Ar 0.5 vol% to 2.0 vol%
・ Gas flow rate 80sccm ~ 160sccm
・ Purity of aluminum target 99.9%
・ Sputtering pressure: 2.7 mTorr to 3.3 mTorr
・ Input power 5 W / cm ^{2 to} 10 W / cm ²
The surface of the aluminum electrode wiring formed under these conditions has a large number of uneven portions, the surface electrode layer has a surface reflectance of 40%, and the formation density of the uneven portions is approximately 30 pieces / 700 μm ² . In addition, each uneven portion t is generally hemispherical with a diameter of 0.5 μm to 1 μm.

  As a result, 20 or more uneven portions t exist in the contact area of the probe needle n of 30 μmΦ. As a result, even when the resist film r is adhered on the uneven portion t, conduction is ensured.

  In addition, this invention is not limited to the form mentioned above, A various change and improvement are possible in the range which does not deviate from the summary of this invention.

  For example, in the above-described embodiment, the case where the probe needle is brought into contact with the pad portion perpendicularly and pressed to crush the concavo-convex portion to achieve conduction between the probe needle and the upper electrode layer has been described. Instead, in a thermal head having an uneven portion on the upper surface of the pad portion, the upper surface of the pad portion may be scratched to inspect while removing the uneven portion.

  That is, even if the pad portion having a smooth upper surface is scratched with a probe needle as in the prior art, the upper surface of the resist film is merely slid, whereas the pad portion having an uneven portion on the upper surface is scratched with the probe needle. In this case, the concavo-convex portion is scraped off by the probe needle, even in the resist film, and the upper electrode layer is newly exposed in the portion where the concavo-convex portion is scraped off by this, the probe needle and the upper electrode layer Can be achieved.

It is sectional drawing of the thermal head which concerns on one Embodiment of this invention. FIG. 2 is a partial enlarged cross-sectional view of the thermal head in FIG. 1. (A)-(c) is sectional drawing explaining each procedure of the inspection method of the thermal head of this invention. It is sectional drawing of the conventional thermal head. FIG. 5 is a partially enlarged sectional view of the thermal head in FIG. 4.

Explanation of symbols

H ... thermal head 1 ... substrate 2 ... glaze layer 3 ... heating element 4 ... individual electrode wiring 5 ... common electrode wiring 6 ... signal electrode wiring 7 ... driver IC
8 ... Sealing resin 9 ... Protective film 10 ... Barrier metal layer p ... Pad part p1 ... Underlying electrode layer p2 ... Overlay electrode layer t ... Uneven part -Resist film B-Solder bump T-Inspection device-S-Stage n-Probe needle n '-The other probe needle R1-Platen roller R2-Transport roller K- ·recoding media

Claims (3)

A substrate, a heat generating element arranged on the substrate, and an electrode wiring electrically connected to the heat generating element, a pad portion formed on a part of the region of the electrode wire, attached to the pad portion A thermal head inspection method for measuring and inspecting electrical characteristics of a thermal head having a resist film by bringing a probe needle into contact with the pad portion,
To form a concavo-convex portion on a surface of the pad portion, at the time of measurement and inspection, presses the probe needles on the pad portion by crushing the uneven portion, the resist film deposited on the surface of the uneven portion the break through, the resist film by removing the inspection method for a thermal head, characterized in that the electrode wire and measuring the probe needle and electrical properties by energizing the test. A substrate, a heating element arranged on the substrate, an electrode wiring electrically connected to the heating element, a pad portion formed in a part of the electrode wiring, and attached to the pad portion A thermal head inspection method for measuring and inspecting electrical characteristics of a thermal head having a resist film by bringing a probe needle into contact with the pad portion,
By forming a concavo-convex portion on the surface of the pad portion, and at the time of measurement inspection, scratching the pad portion with the probe needle, and scraping the resist film attached to the surface of the concavo-convex portion together with the concavo-convex portion, An inspection method for a thermal head, wherein an electrical property is measured and inspected by energizing an electrode wiring and the probe needle. The formation density of the concave-convex portion is 1/700 .mu.m ² or more, 30/700 .mu.m ² inspection method for a thermal head according to claim 1 or 2, characterized in that less.

Images