JPS5814595A - Method of temporarily fixing cylindrical leadless chip part - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for temporarily fixing a cylindrical lead-less step (hereinafter simply referred to as a chip) component, particularly a method for applying a temporary fixing adhesive for mounting a chip component on a printed wiring board. Regarding this, it is possible to apply a fixed amount of adhesive and prevent the chip components from shifting.

In recent years, the use of chip components in consumer devices has been increasing. This means making equipment smaller and thinner.

This is due to its ability to reduce weight and the relative ease of automatic assembly.

Conventionally, as a general method for mounting chip components on the conductor circuit surface of a printed wiring board, adhesive is applied in advance to the position where the chip components of the conductor [11 circuits] are to be mounted by means such as screen printing, and then After placing the chip components, the chip components are temporarily fixed to the printed wiring board by curing or UV curing, and after that, the discrete components are inserted into the printed wiring board, and the circuit is connected using solder dip. It is.

Recently, a method has also been adopted in which discrete components are first inserted into a printed wiring board and then chip components are mounted on the conductive circuit surface.

In the former mounting method, since the chip component is first fixed to the printed wiring board, there is no need to consider heat to other components, and a thermosetting adhesive such as epoxy resin can be used. In the latter mounting method, the chip components are fixed in a later process, so the effect of heat on the discrete components attached first must be taken into consideration. For example, for aluminum electrolytic capacitors, the maximum guaranteed temperature adhesive must cure at 85°C or less.

Also, in the former case, the wiring board is flat and the adhesive can be applied to the printed wiring board using the double IJ+ printing method, but in the latter case, the leaded parts have already been inserted, so The conductor circuit surface has protrusions from cut-clinched lead wires, making screen printing impossible.

Therefore, in such cases, a method using a dispenser is preferred in order to apply the adhesive while avoiding the protrusions.

Conventionally, thermosetting and ultraviolet curing types have been used as adhesives for attaching chip components to printed circuit boards, depending on the purpose, but the characteristics required of these adhesives are (1) It must be able to consistently and consistently apply a fixed amount, (2) It must have a viscosity that prevents the chip components from shifting after the adhesive has hardened, and (3) It must be able to cure at low temperatures in a short time. (4) After the adhesive hardens, the adhesive strength is sufficient to prevent the chip components from falling off during normal processes and soldering, and (6) the adhesive has no adverse effect on the electrical characteristics of the printed wiring board. For example, it should not be affected. In order to meet these required characteristics, conventionally, when applying with a dispenser, the adhesive does not come off from the dispenser nozzle immediately after applying the adhesive, resulting in a stringing phenomenon. Problems such as sticking to the land and not being able to solder occur. Also applied 1
There was a problem that the adhesive also flowed during the several tens of seconds until the chip component was placed, and the applied area spread and came into contact with the lands, resulting in no solder.

Also, cylindrical chips, parts (e.g. 5.91!X2.2φ
) are square chip parts (e.g. 1.eWx s, l'xo
, et), and because of its round shape, there was also the problem that the printed wiring board could easily shift from its normal position when moved.

Additionally, conveyor-type furnaces are common for curing adhesives, but they require a furnace length that matches the production speed, and if the number of production increases with the same equipment, the furnace length must be lengthened. However, the disadvantage is that the equipment itself becomes large.

The present invention provides a completely new method for temporarily fixing chip components that eliminates the above-mentioned drawbacks.The present invention is characterized by the fact that it can be applied as an adhesive in a fixed amount with a dispenser;
There is almost no flow of the adhesive after application, and no deviation occurs even after the chip is placed.

In the method for temporarily fixing cylindrical chip parts of the present invention, the viscosity is 650 poise to 1100 poise (BH type rotational viscometer
118 to 68390-ta 7.2 Orpm, 25°C
), thixotropic index 6.6
~y, s (ASTM D-2566-eeT, BH
type viscometer rotor & 7.25”C, 2rpm viscosity/
2 Orpm), apply an ultraviolet curing adhesive having properties of 0.411 to the conductor circuit surface of the printed wiring board.
Apply with a dispenser with a nozzle diameter of L-0,9111 and mount the hetinop parts on the adhesive. Next, the printed wiring board is introduced into a curing oven using an ultraviolet lamp to cure the adhesive. There is an important relationship between the viscosity of an adhesive and the thixotropic index, and as a result of research experiments, the present inventors have found that the viscosity ranges from 660 poise to 1 as described above.
It has been found that a range of 100 poise is very effective against misalignment of chip components. Furthermore, it has been found that when the thixotropic index is in the range of 6.6 to 7.5, there is no stringing from the nozzle when applying with a dispenser, and a fixed amount can be applied in a short period of time. Viscosity is 660
It is natural that the amount dispensed from the dispenser will be large if there are no poise drops, but it has been reported that the chip components may shift when a slight impact force is applied during the transfer of the printed wiring board after placing the chip components. A problem arises. Further, when the viscosity exceeds 110 poise, although it improves the positioning of chip parts, it becomes difficult to apply with a dispenser. Even if the viscosity exceeds 110 O poise, coating will not be possible if the dispensing time is increased.
7, but the productivity of chip mounting is poor. On the other hand, the pixel tropic index greatly affects the applicability with a dispenser. Generally, liquid synthetic resins containing organic or inorganic pigments such as paints and adhesives have a property called thixotropy.

This refers to the property that the shear stress does not change proportionally to the shear rate, but changes exponentially. On the other hand, fluids that exhibit a proportional change are called Neaton fluids, but they are very difficult to apply with a dispenser because of stringiness. The thixotropic index indicates the degree of thixotropy, and in the present invention, a value of 6.6 to 7.6 was very good on the coating surface. If it is less than 6.6, stringiness will occur and it will adhere to the nearby copper foil lands, impairing soldering properties.

In addition, the adhesive itself flows better and its area gradually expands after application, making it enough to touch copper foil lands and fix chip components. The height will be higher than expected. Furthermore, if the value exceeds 7 or 6, the adhesive loses its viscosity and becomes unable to hold the chip components.

On the contrary, the discharge condition from the dispenser is good and there is no stringiness. As described above, the inventors of the present invention have carefully studied the relationship between viscosity and thixotropic index as adhesives for chip mounting. As a result, the use of adhesives with the above properties is optimal in terms of productivity and characteristics. I found that. It should be noted that ultraviolet rays have a more direct property than infrared rays, and also have a property that they are extremely attenuated by reflection. Particularly in the present invention, if there is an adhesive under a chip component, irradiation with ultraviolet rays becomes impossible when the adhesive is irradiated from directly above because the chip component is in the shadow. Therefore, in order to effectively utilize diagonal light and obtain a uniform illuminance distribution,
By moving the lamp itself, it is possible to irradiate light from an angle and harden the adhesive more deeply and evenly. There are two commonly used UV curing furnaces: a conveyor type (the wrap is fixed and the printed wiring board moves) and a fixed lamp type (the lamp and the printed wiring board are both fixed). It is not possible to irradiate areas that are in the shadows. Therefore, a long period of irradiation is required for sufficient curing, resulting in an extremely large temperature rise in the printed wiring board.

The present invention will be described in more detail with reference to Examples below.

Example 1 As a printed wiring board, thickness of 1.611, 180×2
A wiring board having a size of 2 om and a circuit pattern formed by a conventional method and holes provided at predetermined positions by punching was used. The lands on which chip components are mounted are spaced 6.
Oa, diameter 2.511 A through hole of 0.8 mm was provided in the center of the land. Nozzle diameter 0.711B in the center between the lands,
The ultraviolet curing adhesive was extruded and applied to the wiring board at a pressure of 2.5 Kg/rrt and a discharge time of 0.16 seconds. The ultraviolet curable adhesive contained 65 parts by weight of a methacrylate oligomer (for example, epoxy acrylate).

Methacrylate monomer [e.g. 2.2'bis(4
-acryloxycytoxyphenyl)propan] 45 parts by weight, photosensitizer (e.g. benzoin isobutyl ether) 2 parts by weight, peracid, compound (e.g. t-butyl peroxyacetate) 3 parts by weight, inorganic filler ( 8 parts by weight of silica was used. The properties of the adhesive at this time were a viscosity of 700 voids (25°C) and a thixotropic index of 6.5. The vertical movement distance of the dispenser nozzle is 10m + 1, and the round trip time is 0.46
Seconds. There was no stringing from the nozzle, and the adhesive was applied in a conical shape, and the amount applied at that time was 3.2111p. Also, the area after 60 seconds is 2.1-2.
It was 4-. To this adhesive □ P1 construction f27. Oh (6
, and 2.2$)□.

After introducing it into a curing furnace and allowing it to stand still, it was irradiated with a high-pressure mercury lamp with an effective length of 400 mm and a power of 4 KW at a distance of 1201 B from the wiring board. The irradiation time at that time was 20 seconds. These conditions are shown in the drawings. First, the high-pressure mercury lamp 1 is turned on at point A,
Shutter 2 comes off backward and starts moving to point B. A-B
The spacing is printed wiring board 30 width l (180MI&)
L was set to 2001111 so that it was 10 inches larger than . The going time is 20 seconds, and after finishing, the printed wiring board 3
The surface temperature was 82°C. As the chip component 4, a carbon film resistor made by Matsushita Electronic Components Co., Ltd. is used, and the adhesive strength is 1.39 with a pull tester, and the maximum is 2.
．． 1P, the minimum was 0.9 hairs. No chip components 4 fell off during the subsequent solder dip process (260° C. for 26 seconds).

In addition, in the figure, 6 is an ultraviolet curing adhesive, and 6 is a high-pressure mercury lamp 1.
, and D is a high-pressure mercury lamp 1 and a printed wiring board 3.
It shows the distance from

Example 2 An adhesive with a viscosity of 11 oO poise and a thixotropic index of 7.6 was used in the same manner as in Example 1 (the ultraviolet curable adhesive of Example 1 contained 10 parts by weight of silica). , the same furnace as in Example 1 was used, and the travel distance was 100% longer than the substrate length. As a result, there was no stringing from the dispenser nozzle, and good soldering properties were obtained.

Example 3 A dispenser nozzle with an inner diameter of 0.4M was used, and the pressure was 0.6~. The chip components were temporarily fixed using the same adhesive and method as in Example 1, except that the adhesive was discharged with a pressurization time of 0.8 seconds. As a result, although the amount of adhesive was slightly insufficient, it was possible to temporarily fix the chip components. When a chip component was mounted under the same conditions with a nozzle diameter of 0.9 mm, the amount of adhesive was approximately the appropriate amount, and sufficient adhesive strength was obtained.

Example 4 Dispenser nozzles 0 and 41 were prepared in the same manner as in Example 3.
1B, pressure 6~. When the adhesive was applied with a pressure time of 0.03 seconds, the average adhesive strength was 0.9t, which was a practical strength.

Example 6 Adhesive was applied to 100 points under the same conditions as Example 1 and the weight variation was measured, and the average value □'
3.2'IiI, and the variation coefficient was 4.3%. In other words, the weight change was within ±13 inches from the average value.

1 In the method of the present invention, the pressure applied to the dispenser is 0.5% g to 6.0 g, and the pressurizing time is 0.03 seconds to 0.
．． If the time is 8 seconds, the amount of ultraviolet curable adhesive coming out of the dispenser nozzle can be controlled stably to an appropriate amount.

As described above, the method for temporarily fixing cylindrical leadless chip components of the present invention has a viscosity of 660 to 1100 poise.

The ultraviolet curable adhesive with a thixotropic index of 6.6 to 7.6 is applied to the printed circuit board using a dispenser with a nozzle diameter of 0.4 to 0.911 IB, resulting in faster chimp mounting. The adhesive does not become stringy and can be dispensed in a short period of time, making it easy to apply with a dispenser, providing a stable application state, ensuring that the chip parts are not in the wrong position, and having a practical strength after curing. Sufficient products can be obtained and its industrial value is high.

[Brief explanation of drawings]

The figure is for explaining one embodiment of the method of the present invention. 1... High-pressure mercury lamp, 3... Printed self-wiring board, 4... Chip parts, 6... Ultraviolet valence adhesive, l... Printed. Width of wiring board, L
・・・・・・High) 1-Distance traveled by mercury.

Claims (1)

[Claims] A method for temporarily fixing cylindrical leadless chip components to a printed wiring board using an ultraviolet curable adhesive with a viscosity of 6.
An ultraviolet curing adhesive having properties of 60 poise to 1100 poise and a thixotropic index of 6.6 to 7.6 is applied to the printed wiring board using a dispenser with a nozzle diameter of 0.41EB-0.91111, and one cylindrical lead is applied. A method for temporarily fixing a cylindrical leadless chip component, comprising curing the ultraviolet curable adhesive after placing the leadless chip component.