JPS6014517B2 - Electronic components and wiring board fixed to each other by foamed hot melt and their fixing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wiring board in which electronic components are fixed to the wiring board using foamed hot melt, and a method for fixing the same.

Conventionally, the following two methods have been used to fix electronic components on a wiring board, particularly a printed wiring board, to the wiring board.

1. Using a solvent-based adhesive 2. Using a hot melt Fixation using a solvent-based adhesive as described in item 1 above had the following drawbacks.

In other words, '1' Pollution due to volatile gases generated during bonding work [
2- Gluing work is done manually and is difficult to automate.

{3} Since metal parts such as contacts of micro relays are corroded, a general hot melt method has recently been used.

However, this hot melt also has the following drawbacks. That is, {11) The temperature at the time of dispensing the hot melt is relatively high.

It cannot be used for parts with low heat resistance. '21 During hot melt dispensing work, the hot melt flows down, making it difficult to securely adhere and fix it.

To explain the above state using drawings, Figures 1 and 2
As shown in the figure, electronic components 2 are placed on a wiring board 1.
Since the viscosity of the hot melt 5 discharged is relatively low, it flows down and accumulates on the substrate 1 5b, creating a neck 5a as seen in the figure.

Since the hot melt solidifies in this state, the fixing force decreases. Also, multiple electronic components are close together (
34a, 34b...), the seventh
As seen in the figure, the hot melt did not flow down to the bottom of the electronic component, creating a void. The present invention not only prevents work-related pollution, but also secures electronic components on wiring boards at relatively low temperatures, more reliably, and at lower cost by using foamed hot melt. The purpose is to

The foamed hot melt used in the present invention is an uncoated rubber-based, saturated polyester-based, polyamide-based, polyolefin-based, polyolefin-based copolymer, or a modified product thereof, and is a hot-liquid-rich adhesive. Air or a gas such as N2, CQ, etc. is mixed into the agent as countless closed cells, and their volume is inevitably expanded to about 1.5 to 5 times. These characteristics include not only maintaining the original adhesiveness, but also reducing the amount of raw material adhesive due to a decrease in specific gravity, decreasing the apparent viscosity under high pressure in the applicator, and reducing the flow rate after dispensing. bond(
Key): Deterioration of adhesive properties, thinning of the adhesive layer due to pressure bonding and expansion of its bonding area, resulting shortening of set time, improvement of adhesion to porous and rough surfaces, and rapid cooling of the surface. It has many advantages in adhesive processing, such as expanding low-temperature applications, increasing elasticity, improving sealing performance, extending open time during other operations, and reducing overall costs. That is, by using the foamed hot melt, it is possible to protect electronic components, which most dislike high temperatures, from high temperatures, and to fix them more stably and reliably than with general hot melt. Next, examples will be explained based on two cases: a case of one electronic component and a case of a large number of electronic components. First embodiment: In the case of fixing a single electronic component.

As shown in FIGS. 3 and 4, the foamed hot melt 15 sprayed onto the vertical surface of a single electronic component 12 placed on a printed wiring board 11 is approximately in the sprayed state. (m) That is, the electronic component 12 is solidified in a form of approximately the same size on the upper and lower sides, and the electronic component 12 is reliably fixed on the substrate 11.

Therefore, the neck (neck 5a in FIGS. 1 and 2) that occurs in the conventional hot-bottom ejection as described above is not observed. Second embodiment: When a large number of electronic component groups are fixed at the same time.

In this case, as shown in FIG. 6, the ideal electronic component fixing method is to fix electronic components 22a, 22b, and 22c arranged in groups on one printed wiring board 21 using a foamed hot There are cases where the entire surface is three-dimensionally covered with melt 25 and completely enclosed. The advantage of this fixing method is that electrical insulators are fully enclosed between each electronic component and the wiring board.
{a} Prevent deformation of electronic components due to external forces. {b' Prevent loosening, peeling, and falling off of electronic component mounting parts. tc} Completely insulate electronic components. 'd} Protect electronic components from water and humidity.

'c} Prevents rust on metal parts of electronic components.

[f} Protect electronic components from dust.

As described above, each electronic component is protected from various disturbances, and the operation of the electronic component is ensured and the life of the electronic component is extended.

As a means of implementing the above-described effective filling and encapsulation, an experiment was conducted to compare the use of a conventional general hot melt and the use of a foamed hot melt.

1 Experimental purpose: Comparative measurement of the degree of filling by dispensing hot melt and foaming hot melt onto a group of electronic components on a board.

2 Experimental specifications: {1' Electronic components on the wiring board to be tested.

For basic experiments, a square corrugated plate material (made of PVC) was used as a substitute for the electronic components on the wiring board (see FIGS. 8 to 10).

The height of the mountain is 5 willows x the middle of the mountain is 5 ribs x the distance between the mountains is 4 ribs [2- Dispense nozzle.

Slot nozzle nozzle medium = 50 willow (active = 48 willow) [3- Hot melt.

Yokohama Rubber HM#470 olefin system, viscosity 320 ratio p
s/18000{4} Operating conditions a Temperature 18b Pump pressure 40k9/c Tiger c Usage gas C02d Expansion ratio
4.0e Discharge amount (nozzle)
400 evenings/min (5) Experimental Situation Under the above conditions, the feeding speed of the discharge cloth required to sufficiently fill the valleys of the square corrugated plate was measured, and the results are shown in Table 1 below.

Table 1 Feeding speed for filling square corrugated plates with general type hot melt and foaming type hot melt 150 min/min 300 min 450 min/min - General type hot melt 1.5 no. Less than 20 minutes
2.4 minutes or less Foamed hot melt dispensing products 10.0 M/min or less 14.0 minutes or less 17.0 minutes or less To explain Table 1, similarly, if the speed is less than 10.0 M/min. As shown in Fig. 8, both general type hot melt and foamed hot melt are sufficiently filled up to the valleys of the square corrugated plate, but at higher speeds, as shown in Fig. 9, the valleys are filled. The bottom of the pile will not be filled, and only the surface of the pile will be covered, and if the speed is increased again, the 10th
As shown in the figure, the hot melt adheres only to a portion of the top of the mountain.

As can be seen in the same way, the ratio of the feed speed when dispensing general hot melt and foaming hot melt is 1:6.6.
, 1:7, 1:7.1.

This clearly shows that the dispensing speed of the foamed hot melt is much higher than that of the general hot melt, and that the workability is greater. Although the above was an experiment on a square corrugated plate, substantially the same tendency can be seen for electronic components on actual wiring boards. However, since the arrangement of these electronic components varies widely, it is difficult to publish data, so we will omit it, but the effects on electronic components after dispensing will be described as follows. Diode NEC and Sony foam type and general hot melt type have no heat effect.

Electrolytic capacitors (including titanium capacitors and resistors) 1 In the case of general type hot melt, PVC film is violated, but in the case of foaming type hot melt, it is hardly violated.

Covered insulation resistance with no performance problems 10-130 is good for both foam type and general type hot melt.

As described above, it has been found that foaming type hot melt dispenser does not cause thermal damage to electronic components and can be dispensed at a higher speed. Above, we have explained the products in which electronic components are fixed by foamed hot melt on the wiring board.Next,
We will explain how to fix these products.

Third Example: A method for dispensing foamed hot melt onto a single electronic component will be described.

As shown in FIG. 5, first, the foamed hot melt generated by the foamed hot melt generation applicator 9 enters the discharger 7 through the automatic temperature regulating heat insulating hose 8, and is stored in the discharger 7. The foamed hot melt is discharged from the nozzle 6 through the valve, and is sprayed onto the electronic component 12 mounted on the wiring board 11 and the wiring board 11.
5. At this time, the foamed hot melt 15 dispensed is
It has low susceptibility and sticks to the electronic components 12 and wiring board 11 like whipped cream while being sprayed, solidifies and fixes them by cooling. Incidentally, the discharge operation from the discharge device 7 and the nozzle 6 and the movement of the wiring board 11 can be performed automatically by a timer or pulse transmission.

In addition, manual or semi-automatic methods are of course possible. Fourth Example: In the second example above, a product in which foamed hot melt was sprayed onto a group of electronic components on a wiring board using a slot nozzle was described. Explain the law.

As shown in FIG. 11, electronic components 42a, 42b, 42c, . . . are arranged and attached on a printed circuit board 41.
...Applicator 4 for foaming hot melt generation on the top surface
The foamed hot melt produced in step 9 is discharged in the form of a sheet from a slot nozzle 46 connected to a nozzle of a discharger 47 with a built-in valve through an automatic temperature-controlled heat-insulating hose 48, and the slot nozzle 46 is The substrate 41 can be moved in the "A" direction at a suitable speed, or by fixing the slot nozzle 46 and moving the substrate 41 in the "B" direction at the same speed. Electronic parts groups 42a, 42b, 42c, . It fixes electronic parts. The above-mentioned movement of the slot nozzle or wiring board and discharge of the foamed hot melt can be performed automatically by a timer or pulse generation.

In addition, manual or semi-automatic methods are of course easily possible. Fifth Example: In the third example described above, the foamed hot melt was applied to a group of electronic components on a wiring board through a slot nozzle, but using a general hole-shaped nozzle, This is a method of forming a foamed hot melt in a flat plate shape by discharging it in a zigzag pattern onto the group of electronic components on the wiring board.

FIG. 12 shows the state of dispensing work using the manual gun 57. Needless to say, the feed speed of the manual gun 57 in this operation is determined by the discharge amount of the gun and the thickness of the discharged fabric layer in the same manner as in the second embodiment. In addition, this zigzag dispensing method can be performed using an NC device.
Automatic dispensing is also possible.

As described above, the fixing of electronic components on a wiring board using the foamed hot melt according to the present invention is performed by spraying at a relatively low temperature, so that the electronic components are not damaged by heat and are covered thoroughly, and furthermore, the material is In addition to being a fraction of the cost of conventional products and allowing automation to reduce production costs, this product not only fixes electronic components, but also completely protects them through insulation, waterproofing, moisture-proofing, and rust-proofing effects. This contributes to increasing the lifespan of people.

[Brief explanation of the drawing]

Fig. 1 is a front view of an electronic component fixed using a conventional general type hot melt, Fig. 2 is a side view of Fig. 1, and Fig. 3 is a foamed hot melt applied to an electronic component according to the present invention. Front view when the discharge cloth is fixed with melt, 4th
The figure is a side view of FIG. 3, FIG. 5 is an explanatory diagram of the dispensing process for electronic components using the foamed hot melt according to the present invention, and FIG. Fig. 7 is a state diagram of fixing the dispensed cloth to parts, and Fig. 7 is a state diagram of fixing the dispensed cloth to electronic components placed and mounted on a wiring board, which is often seen in the case of conventional general hot melt. Fig. 9 is a diagram of the filling state of general type and foamed hot melt for a square corrugated plate at an appropriate speed. Fig. 9 is a diagram of the dispensing state when the speed is higher than the above-mentioned appropriate speed. Fig. 10 is a diagram of the filling state in the case of the above-mentioned Fig. 9. Fig. 11 is a diagram showing the state of dispensing when the dispensing speed is higher than the above speed, and Fig. 12 is an explanatory diagram of the work situation in which dispensing is performed using a slot nozzle on a group of electronic components arranged and mounted on a wiring board according to the present invention. FIG. 2 is an explanatory view of the work in which a hand-held gun is used to spray a zigzag pattern onto a group of electronic components arranged and mounted on a wiring board according to the present invention. Explanation of main symbols, 1, 11, 21, 31, 41, 51
...Wiring board, 2, 12, 22a, 32a, 42a
, 52a... electronic component, 5, 17, 35...
... General type hot melt, 15.16, 25, 45,
55... Foaming hot melt, 24a, 34a
...... Spacing between electronic components, 46... Slot nozzle, 56... Hole nozzle. Tsutomu Figure 2 Figure 3 Figure 4 Figure S Figure 6 Figure Aoitsu Figure 8 Figure 9 Figure ll Figure l0 Figure Longevity l2 Figure

Claims (1)

[Scope of Claims] 1. An electronic component and a wiring board on which electronic components are arranged, characterized in that the electronic components are fixed to each other on the wiring board by foamed hot melt. 2. An electronic component and a wiring board characterized in that a slot nozzle sprays foamed hot melt onto a wiring board on which a plurality of electronic component groups are arranged in a flat manner from the upper surface of the electronic component group. How to fix it.