JPH03124458A - Printing head - Google Patents

Abstract

PURPOSE:To form a metallic lead on a film substrate with a sufficient bonding strength to realize a fine pitch by a method wherein metallic layers are plated on the top and rear surfaces of the heat-resistant film substrate having needle holes passing through vertically at predetermined positions, the metallic layers are patterned into a predetermined form, and the top and rear surface of the film substrate are electrically connected with each other at the position of the needle holes. CONSTITUTION:A film substrate 1 made of a heat resistant resin having flexibility, such as polyimide, is formed into a thin and long rectangle. On the right hand side of the film substrate 1, a plurality of needle holes 9 pass through vertically. A metallic lead 2 is formed by laminating a metallic thin film layer 10, a copper plated layer 11, a nickel plated layer 12, and a gold plated layer 13. The metallic leads 2 are directly provided on the top and rear surface of the film substrate 1 and inside the needle holes 9. The metallic lead 2 on the top surface of the film substrate 1 serves as a wiring lead 14, the metallic lead 2 on the rear surface serves as a connection lead 15 connected to an external circuit. These upper and lower leads 14, 15 are connected to each other through the lead of the needle holes 9.

Description

[Detailed description of the invention] [Industrial application field] This invention relates to printheads.

"Prior Art" Conventionally, heat-sensitive type thermal print heads are known as print heads used in printers and the like. This type of print head has a structure in which a large number of heating resistance layers and electrodes are patterned and formed in parallel on a ceramic substrate via an insulating layer using thin film formation technology, and these are covered with an oxidation-preventing layer and an abrasion-resistant layer. ing. To print with this print head, connect the print head to the flexible connector 7.
It is necessary to connect the print head to a drive unit and use this drive unit to selectively generate heat in the heat generating resistor layer of the print head.

However, the print head described above uses expensive materials;
Moreover, since high precision is required for manufacturing, there are problems in that productivity is low and the product is naturally expensive. In addition, this print head must be connected to the drive unit using a flexible connector, but since the print head has an extremely large number of electrodes arranged in parallel at a fine pitch,
Another problem is that the connection work is inefficient.

For this reason, recently, consideration has been given to using a film substrate as a base member and mounting chip components such as IC chips on this film substrate. In other words, in this type of print head, a metal foil is bonded onto a film substrate using an adhesive, and this metal foil is patterned into a predetermined shape using a photolithography method to form metal leads in parallel. In addition to providing a heating resistor layer at the disconnected portion, a drive chip such as an IC chip is directly bonded to the metal lead.

[Problems to be solved by the invention] However, in a print head using a film substrate,
When the pitch of metal leads becomes finer, the adhesive strength of the adhesive that bonds the metal foil becomes insufficient. In particular, when adhesives are heated when bonding chip components such as IC chips, their adhesive strength weakens, causing the metal leads to become misaligned, resulting in problems such as uneven pitch and short circuits. Furthermore, since adhesives generally have low insulation resistance, when the pitch is made finer, the electrical resistance between the metal leads becomes insufficient, causing problems in operation.

This invention was made in view of the above-mentioned circumstances, and enables metal leads to be formed on a film substrate with sufficient bonding strength without using adhesives, enables fine-pitch metal leads, and makes it possible to form metal leads on a film substrate without using an adhesive. The object of the present invention is to provide a print head that can bond chip parts well.

[Means for Solving the Problems] In order to achieve the above-mentioned object, this invention is made by plating the front and back surfaces of a heat-resistant film substrate, which has needle holes penetrating the front and back sides at predetermined locations. By forming a layer and patterning this metal layer into a predetermined shape, a metal lead is formed on the front and back surfaces of the film substrate, the front and back sides are electrically conductive at the location of the needle hole, and a gap is provided for disconnection at a predetermined location. A heat generating resistor layer is formed in parallel with each other, a heat generating resistor layer is applied to the gap between each metal lead, the heat generating resistor layer is covered and protected with an insulating protective film, and the heat generating resistor layer is selectively driven to generate heat.
The C chip is directly bonded to the metal lead.

[Function] According to such a print head, since the metal lead is made of a metal layer adhered to the film substrate by plating, even if the film substrate is used as the base member, the metal lead cannot be sufficiently bonded to the film substrate. Can be formed with strength. Therefore, it is possible to form the metal leads at a finer pitch, and the metal leads are less likely to be misaligned due to heating during bonding of the IC chip, thereby preventing non-uniform pitches, short circuits, etc. Moreover, since no adhesive is used, it is possible to solve operational problems caused by the lack of electrical resistance caused by conventional adhesives.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a printing head. This print head is used, for example, in a facsimile book printer and is capable of line printing. Although not shown, the print head has an elongated rectangular shape as a whole. This print head is provided with a large number of metal leads 2 and a heating resistor layer 3 on a film substrate l, and
Equipped with a plurality of drive chips 4 and control chips 5,
The heating resistor layer 3 is covered with an insulating protective film 6, and these are bonded to supports 7 and h with an adhesive 8.

The film substrate l is made of a heat-resistant resin having I'TFta properties such as polyimide or bismaleimide triazine, and is formed into a long and thin rectangular shape, with a plurality of needle holes 9 (two in Fig. 1) at predetermined locations on the right side. (only shown here, but there are actually many) are formed to pass through the top and bottom. This needle hole 9
is formed into a tapered shape with a diameter of about 0.1 mm using a metal needle with a sharp tip.

The metal lead 2 is made by laminating a metal thin film layer 1O1, a copper plating layer 11, a nickel plating layer 12, and a gold plating layer 13, and is installed directly on the upper and lower surfaces of the film substrate 1 and in the needle hole 9 without using an adhesive or the like. ing. The upper surface side of the metal lead 2 of the film substrate 1 is used as a wiring lead 14 (described later), and the lower surface side is used as a connection lead 15 connected to an external circuit. It is connected. In this case, the wiring lead 1 on the top side
4 are formed in large numbers in parallel at predetermined intervals (for example, intervals of about 0.1 mm) along the longitudinal direction of the film substrate l. Moreover, each of the wiring leads 14 has a gap 16 formed at a predetermined location on the left side in the width direction of the film substrate l, and is disconnected by the gap 16. As a result, each wiring lead 14 is made into a common electrode 17 integrally connected on the left side of the gap 16, the middle part is made into a signal electrode 18, and the right part is made into a connection electrode 19.One signal electrode 18 has a plurality of A set of books (only 7 trees are shown in FIG. 5A, but in reality there are quite a large number of them) are arranged in such a way that the right end of each book surrounds a plurality of drive chips 4, which will be described later. Note that the connection electrode 19 is provided on the right end side of the film substrate l, and is connected to each drive chip 4 and a control chip 5 to be described later.
It is for connecting with.

The heating resistor layer 3 is made of conductive ink such as carbon ink, and is provided thicker than the thickness of the metal lead 2 in each gap 16 of the wiring lead 14 by printing or roll coating. The two electrodes 18 and 17 are electrically connected to each other in a slightly shaped manner. Therefore, when a drive signal is applied to each signal electrode 18 from the drive chip 4, a current flows through the heat generating resistor layer 3 and heat is generated due to Joule heat.

The driving chip 4 selectively outputs a driving signal to each signal electrode 18 of the wiring lead 14.

It consists of an IC chip, is provided on a film substrate l surrounded by the right end side of each signal electrode 18, is bonded to each signal electrode 18 and connection electrode 19 with a gold wire 20, and is sealed with a sealing resin 21. has been done.

The control chip 5 controls each drive chip 4 based on a printing command from the outside, and is an IC chip or L
The connection electrode 19 of the wiring board 14 is made of an SI chip or the like.
Each lead terminal 22 is joined by soldering or the like.

The insulating protective film 6 is made of a heat-resistant resin having wear resistance and oxidation resistance, such as polyimide, and is provided to cover the heating resistor layer 3 and the wiring leads 14 located on the left side of the driving chip 4. The insulating protective film 6 is formed by applying a liquid resin and drying it, or by applying a dry film.

The support body 7 is made of a heat-resistant resin, a flexible metal plate, or the like, and any of these materials should be able to be deformed to some extent. This is to improve the contact of each heating resistor layer 3 with the platen etc. since the print head is long.

Next, with reference to FIGS. 1 to 5, the case of manufacturing the above-mentioned print head will be described. In this case, FIG. 2 shows the manufacturing procedure of the print head, and FIGS. 3 to 5 show the steps of forming the heating resistor layer 3.

First, a tapered needle hole 9 is formed in a film substrate l made of polyimide or the like by penetrating the upper and lower surfaces thereof with a metal needle having a sharp tip. Then, a metal thin film layer 10 of copper or the like is coated on the upper and lower surfaces of the film substrate 1 by vapor deposition or sputtering.

This vapor deposition or sputtering is performed from the upper and lower surfaces of the film substrate l, and the metal thin film layer l is also applied to the inner surface of the needle hole 9 at the same time.
Deposit o. Thereafter, a copper plating layer 11 is formed on the metal thin film layer 10 by electrolytic plating. As a result, the metal thin film layer 10 and the copper plating layer 1 are formed on the upper and lower surfaces of the film substrate l.
A metal layer consisting of 1 is directly formed. In this case, the metal thin film layer lO serves as a base layer for the copper plating layer 11,
It is formed with sufficient bonding strength on the upper and lower surfaces of the film substrate 1 without using an adhesive. Note that this metal thin film layer 10 is preferably made of the same copper as the copper plating layer 11, but is not limited to this, and the copper plating layer 11 is formed with sufficient bonding strength to the film substrate 1 by the metal thin film layer 10. Ru. In this case, the bonding strength is particularly high if the copper plating layer 11 is made of the same metal material as the metal thin film layer 10, but it may be made of a different metal material.

Then, the copper plating layer 11 and the metal thin film layer 10 are etched by photolithography to remove unnecessary portions, and the copper plating layer 11 and the metal thin film layer 10 are patterned in the same shape as the metal lead 2. That is, the copper plating layer 11 and the metal thin film layer 10 are
The surface side corresponds to the wiring lead 14, and the bottom side corresponds to the connection lead 1.
It remains in correspondence with 5. In this case, the copper plating layer 11 and the metal thin film layer 10 corresponding to the wiring lead 14 have a gap 16 formed at a predetermined location on the left side, and the other parts are the common electrode 17 on the left side, the signal electrode 18 in the middle, and the signal electrode 18 on the right side. connection electrode 1
9 and 9 remain corresponding to each other.

The metal thin film layer 1O and the copper plating layer 11 patterned in this way have sufficient bonding strength to the film substrate 1, so they have good heat resistance, and they are also resistant to operational problems due to lack of electrical resistance like adhesives. You can also cancel your hearing.

Thereafter, a nickel plating layer 12 is formed by electrolytic plating on the copper plating layer ll on the lower surface L of the film substrate 1, and a gold plating layer 13 is further formed. As a result, metal leads 2 are formed on both upper and lower surfaces of the film substrate l. At this time, the copper plating layer 11 and the metal thin film layer 10 are
- As described above, since the pattern is formed in a predetermined shape, the nickel plating layer 12 is formed only on the side of the copper plating layer 11, and the gold plating layer 11 is formed on the nickel plating layer 11.
Formed only on the top surface of. Therefore, it is not necessary to perform an etching process on the nickel plating layer 12 and the gold plating layer 13. Moreover, if such a method is adopted, the nickel plating layer 12 and the gold plating layer 13 are not provided on unnecessary parts, so the plating No liquid is wasted and it is economical. Note that the nickel plating layer 12 protects the copper plating layer 11 to provide corrosion resistance, and makes it easier for the gold plating layer 13 to be applied.

The gold plating layer 13 is for lowering the electrical resistance value.

Next, a photoresist 23 is applied to the upper surface of the film substrate 1, covering the wiring leads 14, by a spin cord, dip method, roll coating, or the like. This photoresist 23 is made of an ultraviolet curing photosensitive resin, and its film thickness is 1 to 1.
The thickness can be freely formed up to about 40 gm, and can be arbitrarily set depending on the thickness of the heat generating resistor layer 3, which will be described later. Note that the photoresist 23 may be either a negative type or a positive type, but a case where a negative type is used will be described here.

Thereafter, the photoresist 23 is irradiated with light such as ultraviolet rays through a photomask (not shown). In this case, since the photoresist 23 is of a negative type, the portion of the photoresist 23 corresponding to the gap 16 of the wiring lead 14 is not irradiated with light, but the photoresist 23 of the other portion is irradiated with light. and harden. When the photoresist 23 is developed with a developer, as shown in FIGS. 3A and 3B, only the portion of the photoresist 23 corresponding to the gap 16 of the wiring lead 14 is not hardened and is removed. be done. The portion where the photoresist 23 is removed is formed to be slightly larger than the gap 16 of the wiring lead 14, and the ends of the common electrode 17 and the signal electrode 18 of the wiring lead 14 are slightly exposed.

Next, as shown in FIGS. 4A and 4B, a conductive ink 24 such as carbon ink is printed along the portion where the photoresist 23 has been removed. At this time, the conductive ink 24 only needs to be printed in a strip shape, so high precision is not required in the printing work, and the conductive ink 24 can be easily printed.
can be printed.

Thereafter, as shown in FIGS. 5(A) and 5(B), the photoresist 23 is removed using a removing solution. Then, the conductive ink 24 attached to the top surface of the photoresist 23
is also removed at the same time. As a result, the conductive ink 24 remains only in the gap 16 of the wiring lead 14, and by drying and hardening this conductive ink 24, the heating resistance layer 3
is formed. This heating resistance layer 3 is formed to protrude above the wiring lead 14 by approximately the thickness of the photoresist 23, and is formed to protrude above the wiring lead 14 from the common electrode 17 and the signal electrode 18 of the wiring lead 14.
Connect.

Note that after this, the wiring leads 14 and the heating resistor layer 3 on the left side of the driving chip 4 are covered with an insulating protective film 6 to protect them. After that, the driving chip 4 is placed in a place surrounded by the right end of the signal electrode 18, and each pad electrode of the driving chip 4 and each signal electrode 18 and connection electrode 19 are connected with a gold wire 20 using wire bonding equipment. At the same time, each lead terminal 22 of the control chip 5 is connected to each connection electrode 19 by soldering or the like. At this time, since the metal lead 2 is attached to the film substrate l with sufficient adhesive strength without using an adhesive, the positioning of the gold wire 20 and the soldering of the control chip 5 are not necessary. Finally, by adhering the film substrate 1 to the support 7 with adhesive 8 without causing any displacement or peeling, the print head shown in FIG. 1 is obtained.

Next, the case where thermal recording is performed using the above-described print head will be explained. In this case, the print head is placed on the plantain in advance with the recording paper and the thermal ink sheet sandwiched between them. Corresponding parts can be assigned well. When a print command is given to the control chip 5, the control chip 5
The driving chip 4 is controlled to selectively output a driving signal to each signal electrode 18 of the wiring lead 14, and as a result, a current flows through the heat generating resistor layer 3, and the heat generating resistor layer 3 selectively generates heat due to Joule heat. do. This heat is transferred to the heat-sensitive ink sheet via the insulating protective film 6, and the heat generating resistor layer 3 generates heat.
and melt the ink on the corresponding thermal ink sheet. As a result, the ink on the thermal ink sheet is transferred to the recording paper, and thermal recording is performed.

Note that the present invention is not limited to the above-mentioned embodiments.
may be formed by electroless plating or the like in addition to vapor deposition or sputtering.

The drive chip 4 and the control chip 5 may be integrated into one chip rather than separate chips, and their bonding is not limited to wire bonding or soldering, but may also be done by a flip chip method or by TAB (Tape Automated).
They may be joined by a bonding method or the like. In particular, if the TAB method is adopted, production using a roll-to-roll measuring machine becomes possible, and productivity is extremely high.

Further, the print head is not limited to the above-mentioned heat-sensitive thermal printer, but can also be used as a print head for bubble generation in a bubble-type ink shed printer.

[Effects of the Invention] As described in detail above, according to the print head of the present invention, the metal lead is made of a metal layer deposited on the film substrate by plating.

Even if a film substrate is used as the base member, metal leads can be formed on the film substrate with sufficient adhesive strength. This makes it possible to fine-pitch metal leads, making it possible to
The metal leads are less likely to be misaligned due to heating during chip bonding, and uneven pitches, short circuits, etc. can be prevented. Moreover, since no adhesive is used, it is possible to eliminate operational problems caused by insufficient electrical resistance caused by conventional adhesives. Therefore, according to this print head, each material is inexpensive, high manufacturing technology is not required, and the print head can be easily manufactured, so that productivity can be greatly improved.

[Brief explanation of drawings]

Fig. 1 is an enlarged sectional view of the print head of the present invention, Fig. 2 is a block diagram showing the manufacturing procedure of the print head, and Figs.
The figure shows a process of forming a heat generating resistor layer of a print head. 1...Film substrate, 2...Metal lead, 3...Heating resistance layer, 4...Drive chip, 6...Insulation Protective film, 9... needle hole, 16... gap part. ■ Fig.

Claims (1)

[Scope of Claims] A heat-resistant film substrate having needle holes penetrating the front and back surfaces at predetermined locations, and a metal layer deposited on the front and back surfaces of the film substrate by plating, which is patterned into a predetermined shape. a plurality of metal leads formed in parallel with each other, the front and back sides of which are electrically conductive at the needle holes, and provided with a gap section for disconnection at a predetermined point; and a heating resistor layer deposited in the gap section of each of the metal leads. A print head comprising: an insulating protective film that covers and protects the heat generating resistor layer; and an IC chip that is directly bonded to the metal lead and selectively drives the heat generating resistor layer to generate heat.