JPH0429406Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a urea sensor that detects urea contained in blood or the like.

[Prior art and its problems]

Conventionally, a urea sensor chip 6 in which an enzyme immobilization film is provided on the surface of an ion-sensitive field-effect transistor has a sapphire substrate 1 as shown in FIG.
An ion-sensitive field effect transistor 2 having enzyme membranes 3 and 4 is fixed on one surface of the electrode, and a reference electrode 5 is fixed on the other surface. As shown in FIG. 3, this urea sensor is constructed by fixing a sensor chip 6 to a printed circuit board 7 with an adhesive, and connecting the sensor chip 6 and a pattern 8 on the printed circuit board 7 by wire bonding with a wire 10. The surrounding area is covered with a potting agent 11. FIG. 4 shows a perspective view of a urea sensor in which this sensor chip 6 is mounted on a printed circuit board 7.

When using this urea sensor, blood is dropped onto the sensor chip 6, and the reaction of the enzyme at that time is expressed by the potential difference with the inactivated enzyme, thereby detecting urea in the blood. Therefore, in order for this sensor chip to react normally, the enzyme must be stable. Furthermore, from 1 to actual use
If it is necessary to store the enzyme for two years, it is necessary to keep the enzyme stable for a long period of time, and for this purpose it is necessary to immerse it in water. Therefore, the adhesives and potting agents used need to be water resistant over a long period of time, and if materials with poor water resistance are used, the adhesive or potting agent will peel off, resulting in wire breakage and even damage between wires. This may cause leaks, etc. For this reason, adhesives and potting agents with strong water resistance are selected, but there are limits to their long-term water resistance.

The purpose of the present invention is to eliminate such drawbacks and provide a urea sensor with enhanced water resistance, good quality, and improved reliability by coating wax over the potting agent of conventional sensors. There is a particular thing.

[Means for solving problems]

The configuration of the present invention is to mount a sensor chip having an enzyme immobilized film on the surface of an ion-sensitive field effect transistor and a printed circuit board, and fix the chip and the printed circuit board with an adhesive.
A urea sensor in which the chip and a desired electrode of the printed circuit board are connected by wire bonding, characterized in that the vicinity of the wire is covered with a potting agent, and the surface of the potting agent is covered with wax. .

〔Example〕

FIG. 1 is a cross-sectional view showing an embodiment of the present invention;
FIG. 2 shows the sapphire substrate shown in FIG. 1, on which a transistor 2 is formed, on which a deactivated enzyme-immobilized film 3 and an enzyme-immobilized film 4 are formed, and a reference electrode is separated from them. 5, and together constitute a sensor chip 6.

In FIG. 1, a printed circuit board 7 has a connection pattern 8 for connecting to the sensor chip 6 at one end and a pattern 8' for connecting to a measuring instrument at the other end. The printed circuit board 7 may be flexible, and may be made of polyimide, epoxy, or the like. Further, 9 is an adhesive, and epoxy type is good in terms of water resistance. Further, considering mass production, it is necessary to use a dispenser, and for that purpose, a dispenser with low viscosity is preferable. The sensor chip 6 and the pattern 8 are positioned so as to facilitate wire bonding, and are firmly fixed to the substrate 7 with an adhesive 9. A wire 10 is shown in a bonded state, and is connected between the sensor chip 6 and the pattern 8 at desired points.

When wire bonding the wire 10, if a heated Au wire is used, the heat will have a negative effect on the enzyme, so room temperature Al wire ultrasonic bonding is better. Also, 11
is a potting agent, which is supplied with a dispenser from above the wire 10 to cover the entire surface. The purpose of this potting agent 11 is to protect the wires 10 and also prevent leakage between the wires 10. However, silicone-based potting agent 11 has relatively good water resistance and does not cause any adverse effects such as cutting the wires 10. things are appropriate. 12 is wax, which can be coated over the potting agent 11 to provide complete water resistance. That is, the wax 12 has the effect of completely shutting out water.

[Effect of idea]

As explained above, according to the present invention, the wax completely shuts out water, so even if the urea sensor is immersed in water for a long time, the enzyme will not be deactivated and the sensor function will be satisfied. The reliability is extremely high. Of course, adhesives and potting agents were selected from among many, taking into consideration various conditions.
It's quite effective, but it's not necessarily perfect. Therefore, simply coating with wax as in the present invention can guarantee complete water resistance, which is extremely advantageous.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an implementation of the present invention, FIG. 2 is a cross-sectional view of an example of the chip shown in FIG. 1, FIG. 3 is a cross-sectional view of a conventional sensor chip and printed circuit board, and FIG. The figure is a perspective view showing the overall configuration. 1...Sapphire substrate, 2...Transistor,
3... Deactivated enzyme-immobilized membrane, 4... Enzyme-immobilized membrane, 5... Reference electrode, 6... Sensor chip, 7...
...Printed circuit board, 8, 8'...Connection pattern, 9
... Adhesive, 10 ... Wire, 11 ... Potting agent, 12 ... Wax.

Claims (1)

[Scope of utility model registration request] A sensor chip provided with an enzyme immobilized film and a printed circuit board are mounted on the surface of an ion-sensitive field effect transistor, and the chip and the printed circuit board are fixed with an adhesive, and the chip and the printed circuit board are bonded together. A urea sensor in which desired electrodes are connected by wire bonding, characterized in that the vicinity of the wire is covered with a potting agent, and the surface of the potting agent is covered with wax.