JPH0380356B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a connection using discrete wires between lands provided on the surface of a printed circuit board.

(2) Background of the technology In order to improve signal transmission crosstalk and adjust delay time on multilayer printed circuit boards that are equipped with highly integrated components, the conductor pattern of the printed circuit board is not used as a power transmission line, and the desired distance between lands is improved. are connected with discrete wires, but when the standard grit of the printed circuit board pattern is 50 mil, the land is
Since the distance between the lands is 0.6mm x 0.6mm, the distance between the lands is approximately 0.67mm, so the connection between the lands and the discrete wires is made using a 10μm thick copper conductor wire of 80μmφ on a solder layer approximately 30μm thick plated on the surface of the land. A discrete wire coated with a thick polyurethane film is placed on the wire, and the bonder chip is contacted and pressed from the top of the discrete wire to apply approximately a voltage to the chip.
Heat is applied for 100 ms to melt the polyurethane film and connect the exposed conductive wire to the molten solder.

(3) Prior art and problems Figure 1 shows a method of connecting a land on a printed circuit board and a thin wire, and Figure 2 shows a curve of temperature rise of a chip to which a voltage is applied.

In the figure, 1 is a printed circuit board, 2 is a land, and 3 is a printed circuit board.
is solder plating layer, 4 is flux, 5 is thin line, 6
7 indicates a chip, and 7 indicates a power supply.

As shown in FIG.
The surface area provided on the mill reference grit is 0.6
A solder layer is formed on the top surface of the copper foil land 2 of mm×0.6 mm and approximately 30 μm thick by plating approximately 30 μm thick.
Flux 4 is applied to the top surface of the plating layer, a thin wire 5 made of a copper wire with a conductor diameter of about 80 μm coated with polyurethane about 10 μm thick is placed, and the chip 6 is placed on a lowering device (not particularly shown). After contacting and pressurizing the upper part of the land 2 and the thin wire 5 to be connected by
A voltage of a desired value is applied from the power supply 7 to the heating conductor (not particularly shown) of the chip 6 for about 100 ms to heat the contact end surface of the chip 6 to about 350°C.
After the polyurethane layer on the surface of the solder plate is thermally melted to expose the conductor, the solder plating layer 3 is thermally melted through the exposed conductor by contact with the heated chip 6, and the conductor using the flux 4 and the land 2 are bonded together. A solder connection is made, but the temperature rise curve at the connection end of chip 6 at this time shows that the heating time by chip 6 is approximately
Since the time is extremely short (100 ms), the casing that covers the heating element constituting the chip 6 and conducts the heat of the thermal chip 6 to the connection between the land 2 and the thin wire 5 has a bottom area that makes heating contact. It is made of heat-resistant metal with a volume of 0.35mm x 0.6mm and a height of approximately 2mm, and has a small heat capacity and is easily affected by the heat of the outside air.The land 2 and thin wire 5 are also minute in shape, so they are easily affected by the surrounding temperature. Due to the synergistic effect, when the Y axis is the temperature °C and the X axis is the time ms, as shown in Figure 2,
The temperature at the contact end of the chip 6 rises from room temperature to 350°C with respect to the time of energization to the chip 6, as shown by curve A shown in the figure, and after melting the polyurethane of the thin wire 5 during the rising curve, Soldering is performed in the temperature range, but when the ambient temperature is lower, the temperature rise at the contact end of the chip 6 becomes curve B, and the temperature rise point does not reach 350°C, and the temperature rise between the land 2 and the conductor of the thin wire 5 When the solder connection temperature is low, the solder connection is insufficient, and the ambient temperature is higher, chip 6
The temperature rise at the contact end becomes curve C, and the temperature rise point is 350°C or higher, and the polyurethane layer of the thin wire 5 is thermally melted for a longer length than the desired length, and the exposed length of the conductor becomes longer, and the adjacent pattern is approximately 0.67 mm apart. There is a risk of an accident resulting in electrical contact.

(4) Purpose of the Invention In view of the above-mentioned drawbacks of the conventional art, the present invention provides a method for reliably bonding the land of a printed circuit board and a thin wire coated with polyurethane using a bonder chip without being affected by the ambient temperature of the bonding operation. The object of the present invention is to provide a method for soldering and heating a bonder chip to obtain a desired thermal melting length of a polyurethane coating.

(5) Structure of the Invention According to the present invention, the solder plated land of the printed circuit board and the chip of the bonder for the heat pressure wire of the fine wire coated with polyurethane are heated during heat pressure welding. At the pressure welding position, increase the voltage at the beginning of voltage application,
This is achieved by a thin wire connection method characterized in that the applied voltage is then lowered over time to a predetermined value and the predetermined value is maintained for a predetermined period of time.

(6) Examples of the invention Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 3 shows the temperature increase of the heated chip of the bonder according to the present invention, and FIG. 4 shows the method of increasing the temperature of the heated chip of the bonder according to the present invention. When connecting the thin wire 5 of the discrete to the land 2 of the printed circuit board 1 by soldering, the shape of the heating chip 6 of the bonder is small, the heat capacity is small, and the temperature dependence of the ambient temperature is large, so it is difficult to solder the connection. Sex and thin lines 5
To avoid problems due to excessive heat melting of the polyurethane coating, in the present invention, the temperature rise curve of the chip 6 is shown in the conventional curve A, and the duration of the saturation temperature of 350°C on the contact surface of the chip 6 is 10 ms. As shown in the D curve, the duration of the saturation temperature is
This effectively increases the apparent heat capacity of the chip 6, reduces the temperature dependence of the chip 6 on the temperature of the outside air surrounding the chip 6, and ensures stable soldering and polyurethane connections. This is done to obtain the desired length of peeling by thermal melting of the coating, and for this purpose a voltage is applied to the heating element of the chip 6.
As shown in FIG. 4 in a time period of 100 ms, the Y-axis is the applied voltage V, the X-axis is the voltage application time ms, and the conventional voltage application curve to the chip 6 is E, and the voltage application according to the present invention is applied. When the curve is F, the E curve has the same value during the conventional voltage application period, whereas in the present invention, the F curve has the same value at the beginning of voltage application. On the other hand, as shown in the F curve, by increasing the voltage value compared to the conventional value and decreasing the voltage over time to reach the conventional value, the third
As shown by curve D in the figure, the temperature rise is assumed to be rapid and the voltage is applied to reach the saturation temperature within 50 ms.

By applying this voltage with a stepped voltage, it is possible to easily obtain a desired temperature rise curve.

(7) Effects of the invention As explained in detail above, by making the duration of the saturation temperature of the temperature rise of the heating chip of the bonder that connects the land of the printed circuit board and the discrete thin wire for a longer time, By ensuring the solder connection between the land and the thin wire and by preventing excessive peeling of the polyurethane coating on the thin wire, the reliability of the solder connection is ensured. This has been very effective in preventing contact.

[Brief explanation of drawings]

Fig. 1 shows the connection method between the land of the printed circuit board and the thin wire, Fig. 2 shows the temperature rise and curve of the chip to which voltage is applied, and Fig. 3 shows the temperature rise of the heated chip of Honda according to the present invention. , FIG. 4 shows a method of increasing the temperature of a heated chip of a bonder according to the present invention. In the figure, 2 is the land, 3 is the solder plating layer, and 5
6 indicates a thin line, and 6 indicates a chip.

Claims (1)

[Claims] 1 The soldered land of the printed circuit board,
During heat pressure welding, the voltage is increased at the beginning of the voltage application to the bonder chip for heat pressure welding of thin wires coated with polyurethane at the heat pressure welding position, and then the applied voltage is increased to a predetermined value over time. A method for connecting thin wires, characterized by lowering the wire to a certain value and maintaining the predetermined value for a certain period of time.