JPS58206671A - Laser-resistant protective paint - Google Patents

Abstract

PURPOSE:To prepare the titled paint having masking effect to laser beam and capable of maintaining the insulation of an insulating film after laser trimming, by dispersing an inorganic filler opaque to laser beam in a thermosetting or thermoplastic organic synthetic resin. CONSTITUTION:The objective paint is prepared by dispersing preferably 40- 90wt% of an inorganic filler which is opaque to laser beam (preferably boron nitride, alumina, talc, lithopone, or kaoline having a particle diameter of <=10mum) in a thermosetting organic synthetic resin (e.g. epoxy resin, phenolic resin, alkyd resin, etc.) or a thermoplastic organic synthetic resin (e.g. teflon resin, polyethylene resin, polyester resin, etc.).

Description

[Detailed description of the invention] The present invention relates to a laser-resistant film-retaining coating.

Laser light has conventionally been used for trimming carbon resistors or nickel-plated resistors provided on hybrid integrated circuit boards to adjust their resistance values.

However, such laser light has the disadvantage that it not only burns out the resistor material but also damages the insulating resin underneath. For this reason, when a denomination is used as a hybrid integrated circuit board, there is a risk that a show-off with the board may occur.

The present invention was made to improve these drawbacks, and provides a new laser-resistant protection! The company provides paints to

An embodiment of the present invention will be described in detail below with reference to FIGS. 1 and 2.

The laser-resistant S-retaining paint according to the present invention is an electrically insulating material composed of a thermosetting or thermoplastic organic synthetic resin containing an inorganic filler that does not transmit laser light dispersed therein.

As the thermosetting organic synthetic resin, epoxy resin, phenol resin, melamine resin or alkyd resin is used.
As the thermoplastic organic synthetic resin, Deflon resin, polyethylene resin, and polyester resin are used.

Inorganic fillers include boron nitride (BN), alumina (Ae, o, ), and talc (3Mp; 0.
4SiO=A), lithopone (BaSα@zns) or kaolin (A/.

One or a mixture of α・2Siα・2ru0) is used.

The laser transmittance of the laser-resistant protective coating according to the present invention is shown in diagram M1. In Figure 1, the X-axis is the inorganic filler content (% by weight), and the Y-axis is the laser transmittance (%).
It is. Since the laser light that passes through the protective paint is scattered in the process and its energy density decreases, a protective effect can be obtained if the transmittance is 50% or less. The solid line indicates the characteristics due to talc, and the film thickness is 10 μm, 119 μm, 135 μm, 144
This is the case where μm is 163 μm. The dotted line indicates the characteristics of alumina, and the film thickness (f-12p m, 35 μm
% 60 am. Accordingly, from Figure 1, the laser transmittance is 50% at the film thickness of the protective paint used.
The content of the inorganic filler may be determined as follows.

However, if the film thickness is 70 μm or more, cracks may occur due to heat cycling, and insulation cannot be maintained. Therefore, the practical film thickness is 20 to 70 μm. Therefore, in the case of a protective paint containing Merck, the filler content must be about 40% or more in order for the laser transmittance to be 50% or less from the solid 63 μm curve.

Furthermore, when the filler content is increased, the function of the organic synthetic resin that binds the filler is lost, making it easier for cranks to enter the coating, and it no longer functions as a protective coating. Therefore, the upper limit of the filler content is about 90%.

Therefore, the filler content is in the range of 40 to 90% by weight, and the laser transmittance is 50% according to the characteristics shown in Figure 1 of each protective resin.
% or less.

Next, the particle size of the filler particles in the laser-resistant WI & paint according to the present invention also affects the transmittance of laser light. FIG. 2 shows the transmittance of laser light for a protective coating with a filler content of 64% by weight and a film thickness of 8 to 12 μm. The solid line shows the characteristics when kaolton with an average particle diameter of 0.55.2.4 μm is used as a filler. If the average particle size of the filler becomes larger than the wavelength of the laser beam, the scattering effect becomes larger and a protective effect can be obtained. Since the wavelength of the YAG laser beam is 1060 Jan, the average particle size of the filler is 1 srn or more.
Since the average particle size of the filler is 30 μm, a protective effect can be obtained when the average particle size of the filler is 0.5 μm or more. Practically speaking, the scattering effect is greatest when the average particle size of the filler is about three times the wavelength of the laser beam.

On the other hand, if the average particle size of the filler is 10 μm or more, the screen may become clogged when a coating film is formed by screen printing. Therefore, the average particle size of the filler is 10g.
Must be less than m.

As detailed above, the laser-resistant protective coating according to the present invention can obtain a masking effect against laser light simply by containing an inorganic filler that is opaque to laser light.As a result, the laser-resistant protective coating according to the present invention If a carbon resistor or the like is formed on the substrate, the insulation properties of the underlying insulating film can be maintained even after laser trimming. Furthermore, the laser-resistant protective coating according to the present invention allows multilayering of resistors and laser trimming of the upper resistor.

[Brief explanation of the drawing]

FIGS. 1 and 2 are characteristic diagrams explaining the present invention in detail. Fig. 1 (o/,) Filler 41 stitches p (!t) Fig. 2

Claims (1)

[Claims] 1. A laser-resistant protective paint characterized by containing a thermosetting or thermoplastic organic synthetic resin dispersed with an inorganic filler that does not transmit laser light. 2. The laser-resistant protective paint according to claim 1, characterized in that the inorganic filler is one or more of poron nitride, alumina, Merck, Suitobon, and kaolin. 6.% The laser-resistant protective coating according to claim 1, characterized in that the inorganic filler is contained in an amount of 40 to 90% by weight. 4.% The laser-resistant protective coating according to claim 1, wherein the inorganic filler has an average particle size of 10 μm or less.