JPH0356068Y2 - - Google Patents

Description

[Detailed description of the invention] (Industrial application field) This invention aims at reducing solderability due to the diffusion of heat to the metal base when bringing out terminals from a metal base board (metal base printed wiring board), and This invention relates to a metal-based printed wiring board that can suppress the occurrence of solder bridges and reliably lead out terminals from a metal substrate.

(Prior art) Conventionally, terminals have been brought out from metal boards by hand soldering using a soldering iron with a high wattage, or by joining other parts at the same time as reflow joining a flexible board.
Hand soldering has poor work efficiency as heat is transferred to the metal base, and simultaneous reflow has poor workability (handling) as the flexible board remains attached to the metal board after the reflow process, and heat during reflow is poor. As a result, there were drawbacks such as the flexible substrate easily lifting from the joint.

Therefore, a method has been considered in which an organic substrate (organic substance-based printed wiring board) 3 is directly mounted on a metal base substrate 1 via solder 5 paste and reflow bonded. There is a risk that the solder 5 paste sandwiched between the boards will be crushed, resulting in solder bridging or poor bonding at the adjacent lands 4. a is a side view, b
is a plan view.

These problems become more noticeable when lands, including circuit patterns, are brought close to each other in order to mount components at high density.

(Purpose of the invention) The purpose of the invention is to obtain a terminal that can be easily taken out from a metal substrate. By using this terminal, it became possible to finally join the flexible substrates together by thermocompression bonding or the like.

(Outline of the invention) The metal-based printed wiring board of the present invention consists of a metal-based printed wiring board, an organic-based printed wiring board having a terminal land, and a chip component with electrodes arranged at both ends and surface-mounted on the printed wiring board. The organic substance-based printed wiring board is electrically mounted on the metal-based printed wiring board with the chip component interposed between both substrates corresponding to the conductor lands provided on the mutual board surfaces. , and terminals of the metal-based printed wiring board are connected to the organic-based printed wiring board through terminal lands of the organic-based printed wiring board.

(Embodiment of the invention) The invention will be described below with reference to FIG. FIG. 2 shows an example of terminal output from a metal substrate according to the present invention. FIG. 2a shows a state in which a chip component 2 is mounted on a metal substrate 1. The conductor land 4 is present only on one side of the chip electrode. Print the solder 5 paste and then mount the chip component on the board 1. The chip component 2 used is usually a jumper chip, but it may also be a resistor, capacitor, etc. chip if necessary.

Next, the printed solder 5 paste is mounted on the organic substrate 3, and reflow bonding is performed (FIG. 2b). Since there is a space between the boards equal to the thickness of the chip, solder bridges do not occur. That is, the organic substrate is thermally isolated from the metal base by being slightly floating. After making the terminals, solder 5 paste is printed on the flexible substrate 6 as shown in FIG.
Further, even when hand soldering is performed, since the chip component 2 is interposed between the boards, there is little heat diffusion, so soldering can be performed easily.

Further, FIG. 4 shows a plan view of the embodiment, and the organic substrate 3
The lands 4 on the upper and lower surfaces are electrically connected through the through holes 8, and the lands 4 on the metal base substrate 1 and the exposed lands 4 on the upper surface of the organic substrate 3 are electrically connected, so that they form so-called terminal terminals (lands). ).

Since the chip is lightweight and easy to move, it is drawn to the target land by the surface tension of the solder, and its position is automatically corrected during reflow. Therefore, even when the chip is misaligned during mounting, this correction effect moves the chip components to the appropriate position, making it difficult for bonding defects to occur.

That is, since the electrical connection between the two substrates is made through the solder joint between the chip component and the land, the movement of the chip component during reflow can be utilized to improve the reliability of the bonding between the two substrates.

Additionally, organic substrates such as paper-phenol base materials may warp due to heating during reflow;
In the configuration of the embodiment, as shown in FIG. 3, since the connection with each board is through the connection with one electrode of the chip component, even if the chip component is attracted to each land when the board is warped, Bonding defects are less likely to occur.

(Effects of the invention) As described above, the invention is effective in bringing out terminals from a metal substrate, and has the following effects.

The heat insulation effect (preventing heat escaping to the metal base) of the chip components and organic substrate suppresses the diffusion of heat to the metal substrate during soldering, improving solderability.

Even if the land spacing is narrowed, the paste does not spread and is less prone to solder bridging and poor bonding compared to types that directly reflow bond the board to the metal board. Therefore, it is advantageous for high density.

Since the chip components move to the proper position during reflow due to the surface tension of the solder in response to misalignment during mounting, bonding defects are less likely to occur.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining a conventional example, FIGS. 2 and 4 are diagrams for explaining the structure of an embodiment, and FIG. 3 is a diagram for explaining another embodiment. Explanation of symbols, 1...Metal (base) substrate, 2...
...Chip parts, 3...Organic substrate, 4...(Conductor)
Land, 5...Solder, 6...Flexible board, 7...Heater, 8...Through hole.

Claims (1)

[Scope of utility model registration request] A metal-based printed wiring board, an organic-based printed wiring board having a terminal land, and a chip component having electrodes on both ends and surface-mounted on the printed wiring board, and conductive lands provided on the mutual board surfaces. The organic-based printed wiring board is electrically connected to the metal-based printed wiring board with the chip component interposed between both boards correspondingly, and the terminal output of the metal-based printed wiring board is connected to the A metal-based printed wiring board characterized in that the terminal land is formed on an organic-based printed wiring board.