EA041721B1 - THIN-FILM TITANIUM THERMISTOR ON A FLEXIBLE POLYIMIDE SUBSTRATE AND METHOD FOR ITS MANUFACTURE - Google Patents

Description

The technical solution relates to instrumentation, namely to thin-film thermistors and methods for their manufacture. Such thin-film thermistors are designed for discrete level meters and can be used to control the level and mass flow of fuel components during refueling, consumption and storage in the chemical, space and other industries.

The prototype of the claimed technical solutions is the construct of a thin-film titanium thermistor on a polyimide substrate according to Fig. 1, shown in the applicant's patent RU 2295115 C2 dated March 10, 2007, IPC G01F23/00, G01F1/68, called Liquid level control sensor [1]. In [1] (Fig. 1) a thin-film titanium thermistor on a flexible polyimide substrate (hereinafter referred to as the thermistor) of a rectangular shape is presented, on which a meander-shaped film resistor (hereinafter referred to as the meander of the thermistor) is placed in the center, along the edges of the long side of the rectangular substrate (on its short sides) there are contact pads, which are connected to the thermistor meander in the form of wedges, the thermistor meander is made in a point design. From the description of the invention [1], it is known that a thin-film titanium thermistor on a polyimide substrate is made of a rectangular shape with dimensions: length 9 mm, width not more than 2.5 mm and thickness 10...50 μm, with a titanium film thickness not more than 0.005 mm. The meander of the thermistor is made in a point design on an area of not more than (0.15...0.5)x(0.15...0.5) mm and a titanium film thickness of not more than 0.15 µm.

The remaining (other) parameters of the thermistor [1] were not disclosed and were the applicant's know-how, because the prototype invention claimed not the thin-film thermistor itself, but the liquid level sensor assembly.

The method for manufacturing thin-film titanium thermistors on a flexible polyimide substrate according to the prototype device [1], as well as other known similar devices, consists in sequential deposition of adhesive layers and a resistive layer and a contact layer onto a thin dielectric substrate, selective photolithography and etching to form thin-film thermistors.

The disadvantage of the prototype [1], as well as the method of its manufacture, is that the thin-film thermistor included in its composition cannot be manufactured without disclosing the know-how of the applicant, including without specifying and specifying the parameters of the materials of its components, as well as without specifying specific dimensions, ranges of their change and technological regimes.

The disadvantages of the device and the method of its manufacture according to [1] pose the problem of improving the manufacturability of the design, i.e. optimization of its dimensions and materials used, as well as simplification of the manufacturing technology of the device by improving the manufacturing technology (method) to improve the accuracy of obtaining geometric dimensions.

The essence of the claimed device is that a thin-film titanium thermistor on a flexible polyimide substrate (hereinafter referred to as the thermistor) is rectangular in shape, on which a film resistor in the form of a meander (hereinafter referred to as the meander of the thermistor) is placed in the center, along the edges of the long side of the rectangular substrate (on its short sides) there are contact pads, which are connected to the thermistor meander in the form of wedges; the meander of the thermistor is made in a dot design. The substrate is made of a thin heat-insulating material - polyimide with a thickness of 25 ... 125 microns, a rectangular substrate has dimensions of 4 ... 6 mm long and 0.8 ... 2.0 mm wide, the meander of the thermistor occupies an area 1 mm)...(0.3x0.3 mm), the meander of the thermistor is made of a resistive layer of titanium 0.1...0.2 µm thick, the contact pads of the thermistor are made of a copper layer 1.5...3 thick, 0 µm, and a 0.02-0.03 µm thick chromium layer is used as an adhesive sublayer between the titanium and copper layer, and a chromium layer 0.02-0.05 µm thick is used as a protective layer for copper.

The essence of the claimed method lies in the fact that the method of manufacturing thin-film titanium thermistors on a flexible polyimide substrate, consisting in sequential deposition of adhesive words and a resistive layer and a contact layer on a thin dielectric substrate, selective photolithography and etching to form thin-film thermistors. As an adhesive and resistive layer, titanium 0.1 ... 3.0 µm and a protective layer of chromium with a thickness of 0.02-0.05 µm, then selective photolithography with etching is performed sequentially in four stages with the formation of thin-film thermistors, namely, at the first stage, the total layer is removed, at the second stage, a titanium film resistor is formed, at the third stage, copper pads are formed; at the fourth stage, windows are opened in the protective chromium layer to cover the copper pads with a solder layer, the substrate is divided into separate thermistors, each of which has their pads covered with a layer of solder, soldered onto an individual printed circuit board of the sensor flip-chip technology and carry out electrical training of each thermistor.

The essence of the claimed device and method of its manufacture is illustrated by graphic materials.

- 1 041721

In FIG. 1 is an enlarged side view of the thermistor in section - the structure of the thermistor in longitudinal section.

In FIG. 2 is a plan view of a thin film platinum thermistor on a flexible polyimide substrate, where 1 is a flexible polyimide substrate; 2 - thermoresistive layer of titanium; 3 - adhesive sublayer of chromium; 4 - contact layer of copper; 5 - protective layer of chromium; 6 - protective layer of varnish; 7 - meander of the thermistor from the thermoresistive layer of titanium.

In FIG. Figure 3 shows the stages of manufacturing titanium thermistors on a flexible polyimide substrate: on the left - layer structures, on the right - the pattern obtained after etching.

Fig. 3a): layers are sequentially deposited on the substrate, namely, the resistive layer of titanium - 2; adhesive sublayer of chromium - 3; copper contact layer - 4; protective layer of chromium - 5.

Fig. 3b): after removing the deposited layers using photomask no. 1, the topology of the total layer remains on the substrate, from which the thermistor is formed.

Fig. 3c): after opening the window - removing the layers of chromium and copper from the surface of the resistive layer using photomask No. 2 - a film resistor was formed in the center of the substrate.

Fig. 3d): after opening the windows - removing chromium from the copper surface using photomask No. 3 - copper contact pads were formed on the edges of the board for tinning and soldering the thermistor to the printed circuit board.

In FIG. Figure 4 shows an enlarged view of the meander of a thin-film titanium thermistor with its dimensions.

In FIG. 5 is a plan view of the claimed thin film platinum thermistor on a flexible polyimide substrate.

In FIG. 6 - sensor (for the sensor) with a thin-film titanium thermistor soldered to the board with three point-type resistors located on one flexible polyimide substrate with contact pads located on opposite sides of the long side of the substrate (on its short sides).

The device - the claimed thermistor - consists of sequentially deposited on a thin flexible polyimide substrate (1) layers of a thermally resistive titanium layer (2), an adhesive chromium sublayer (3), a copper contact layer (4), a protective chromium layer (5) and a protective layer of varnish (6), which is covered with a meander (7), formed from layers of a thermoresistive layer of titanium (2). A thin-film titanium thermistor on a flexible polyimide substrate (hereinafter referred to as the thermistor) is made on a rectangular-shaped substrate (1), on which a meander-shaped film resistor (7) (hereinafter referred to as the thermistor meander) is placed in the center from a thermally resistive layer of titanium (2). Along the edges of the long side of the rectangular substrate (1) (on its short sides) there are contact pads, which are connected to the thermistor meander in the form of wedges. The meander (7) of the thermistor is made in a dot design. The rectangular substrate (1) has dimensions of 4...6 mm in length and 0.8...2.0 mm in width and is made of polyimide with a thickness of 25...125 μm. The meander (7) of the thermistor occupies an area (0.1x0.1 mm)...(0.3x0.3 mm) and is made of a resistive titanium layer (2) 0.1...0.2 µm thick. The contact pads of the thermistor are made of a layer of copper (4) 1.5...3.0 µm thick. A layer of chromium (3) with a thickness of 0.02-0.03 µm was used as an adhesive sublayer between the layer of titanium (2) and copper (4). A layer of chromium (5) with a thickness of 0.02-0.05 µm was used as a protective layer for copper (4).

A method for manufacturing thin-film titanium thermistors on a flexible polyimide substrate consists in sequential deposition on a thin dielectric substrate (1) of a thermally resistive titanium layer (2), an adhesive chromium sublayer (3), a copper contact layer (4), a protective chromium layer (5). As an adhesive and resistive layer, titanium (2) with a thickness of 0.1 ... 4) with a thickness of 1.5...3.0 µm and a protective layer of chromium (5) with a thickness of 0.02-0.05 µm. Next, sequentially in four stages (No. 1, 2, 3 and 4) selective photolithography with etching is performed to form thin-film thermistors in the form of a meander (7) formed from a thermally resistive layer of titanium (2). The steps of selective photolithography are as follows:

the first stage is the removal of the summary layer;

the second stage is the formation of a titanium film resistor;

the third stage - the formation of copper pads;

the fourth stage is the opening of windows in the protective chromium layer to cover the copper contact pads with a layer of solder.

After that, a meander (7) is covered in each thermistor with layers of a thermoresistive layer (2) brought to it by wedges and covered with a protective layer of varnish (6). Next, the substrate (1) is divided into separate thermistors, each of which has their contact pads made of copper (4) covered with a layer of solder. Coating with a solder layer of contact pads made of copper (4) of each thermistor can be carried out on one (large) substrate before its separation (cutting) into separate thermistors, which further increases the manufacturability of production and reduces its cost.

After separation into separate thermistors, the latter (them) are soldered onto an individual printed circuit board (8) of the sensor using flip-chip technology and each thermo-resistor is electrically trained.

Claims (2)

sea resistor. The specific design of the claimed device and method for its implementation, which are implemented and tested by the applicant, is given below. The substrate is made of a thin heat-insulating material - polyimide - 25 thick, the rectangular shape of the substrate (1) has dimensions of 5.0 mm long and 1.0 mm wide, the meander (7) of the thermistor occupies an area of 0.2x0.2 mm and is made of a resistive layer titanium (2) with a thickness of 0.15 microns, the contact pads of the thermistor are made of a layer of copper with a thickness of 2.0 microns. A 0.025 µm thick chromium layer was used as an adhesive sublayer between the titanium (3) and copper (4) layers. A layer of chromium (6) with a thickness of 0.03 µm was used as a protective layer for copper (4). A method for manufacturing thin-film titanium thermistors on a flexible polyimide substrate consists in sequential deposition onto a thin flexible polyimide substrate (1) of layers of a thermally resistive titanium layer (2), an adhesive chromium sublayer (3), a copper contact layer (4), a protective chromium layer (5) and a protective layer of lacquer (6), which is covered with a meander (7) formed from layers of a thermally resistive titanium layer (2). Titanium 0.15 µm thick is used (applied) as an adhesive and resistive layer, on which an adhesive chromium layer 0.025 µm thick, a copper contact layer 2.0 µm thick and a protective chromium layer 0.03 µm thick are sequentially applied. Next, the selective etched photolithography described above in four steps is performed sequentially to form thin-film thermistors. After that, the substrate is divided into separate thermistors, each of which has their contact pads covered with a layer of solder, soldered onto an individual printed circuit board of the sensor using flip-chip technology, and each thermistor is electrically trained. According to the claimed technical solutions, devices (thermistors) with several film resistors can be manufactured, for example, shown in Fig. 6 is a thermistor device with combined point-type resistors located on one polyimide substrate. Literature. 1. A thin-film titanium thermistor on a rectangular flexible polyimide substrate, on which a meander-shaped film resistor is placed in the center, and on the short sides of the rectangular substrate there are contact pads, which are connected to the thermistor meander in the form of wedges, and the thermistor meander is made in a point design, characterized in that the substrate is made of a thin heat-insulating material - polyimide - 25 ... 125 microns thick, the rectangular substrate has dimensions of 4 ... 6 mm in length and 0.8 ... 2.0 mm in width, the thermistor meander occupies an area from 0.1x0.1 to 0.3x0.3 mm; µm, and a chromium layer 0.02...0.03 µm thick is used as an adhesive sublayer between the titanium and copper layer, and a chromium layer 0.02...0.05 µm thick is used as a protective layer for copper. 1. Patent for the invention of the Russian Federation: RU 2295115 C2 dated 03/10/2007, IPC G01F 23/00, G01F 1/68, called Liquid level control sensor. CLAIM 2. A method for manufacturing thin-film titanium thermistors on a flexible polyimide substrate, consisting in sequential deposition of an adhesive and resistive layer and a contact layer on a thin dielectric substrate, selective photolithography and etching to form thin-film thermistors, characterized in that titanium is applied as an adhesive and resistive layer with a thickness 0.1 ... 0.2 μm, on which an adhesive layer of chromium with a thickness of 0.02 ... 0.03 μm, a contact layer of copper with a thickness of 1.5 ... 3.0 μm and a protective layer of chromium with a thickness of 0 02...0.05 µm, then selective photolithography with etching is performed sequentially in four stages with the formation of thin-film thermistors, namely, at the first stage, the total layer is removed, at the second stage, a titanium film resistor is formed, at the third stage, copper contact pads are formed and at the fourth stage, windows are opened in the protective layer of chromium to cover the copper contact pads with a layer of solder, after h it is divided by the substrate into separate thermistors, each of which has their contact pads covered with a layer of solder, soldered onto an individual printed circuit board of the sensor using flip-chip technology, and each thermistor is electrically trained. -