JPH0510382Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to an improvement in the structure of a hybrid IC that can increase packaging density without impairing reliability.

[Summary of the idea]

Hybrid ICs, which consist of two thick-film circuit boards stacked one on top of the other and fixed at both ends with F-shaped lead frames, are prone to problems due to their thickness, especially if conductors are cross-wired on the inner surface of the stacked boards. However, there were problems such as a level difference at the edge of the circuit board, and when it was fixed with a lead frame, stress caused cracks. In the present invention, in order to eliminate this problem, a spacer is inserted between the terminal portions of the lead frames of multiple thick film circuit boards, and these are overlapped to realize higher-density mounting.

[Conventional technology]

Figure 3 shows a cross-sectional view of a hybrid IC with a multilayer structure that is currently in practical use. 1A and 1B are thick film printed boards, 3 is a lead frame, 4 is a clip portion of the lead frame 3, 5 is a multilayer upper conductor formed on the thick film printed board 1B, 6 is an insulating glass,
7 is a through hole, 8 is a front conductor, 9 is a back conductor, and 10 is a resistor. In this conventional example, the film thickness of the insulating glass 6 is about 40 μm, the film thickness of the multilayer upper conductor 5 is about 10 μm, and there is a gap of about 50 μm between the thick film printed circuit boards 1A and 1B, as estimated from normal thick film printing technology. It turns out. To assemble the hybrid IC, in this state, both ends of the thick film printed circuit board are sandwiched between the F-shaped lead frames 3, the clip portions 4 are deep soldered, and then the entire hybrid IC is coated with a molding material. For coating, for example, a molding material is applied and then heat treatment is performed at 120°C for about one hour, but there was a problem in that internal stress caused cracks in the thick film circuit board starting from the through holes 7. The reason for this is that the force holding down the two thick-film printed circuit boards with the lead frame and the force directed from the inside to the outside of the overlapping surfaces due to thermal expansion of the heat-treated material act in opposite directions, and the multilayer upper conductor 5 It is believed that the height of the insulating glass 6 acts as a fulcrum and causes stress to concentrate on the through-hole portion due to a lever action, causing a crack. Furthermore, thick-film printed substrates (commonly known as white substrates) already have a warpage of about 50 μm, so if these substrates are stacked on top of each other, the stress described above will be further exacerbated.

In order to avoid the above problems, it is possible to fill the gap between thick film circuit boards A and B with buffer material, or print dummy insulating glass, conductor, etc. as a spacer on the edge of the thick film circuit board. .

However, this method lacks reliability and stability due to the interference of delicate parameters such as variations in the filling amount of the buffer material and variations in the film thickness of the spacer. In addition, we design hybrid ICs by carefully setting each parameter over a long period of time.
Even if the assembly work is stabilized, this method becomes a completely cut-and-try method if the positions of cross wiring and through holes change for each thick film printed circuit board.
The production design was inefficient.

[Problem that the invention attempts to solve]

This invention was devised in view of the above-mentioned problems, and consists of stacking multiple thick-film circuit boards to create a structure that relieves stress from each part.The purpose is to extend the conventional technology without reducing reliability. Our goal is to provide more integrated hybrid ICs through on-line production.

[Means for solving problems]

In order to achieve the above object, the present invention creates a through hole in the part of the conventional thick film printed circuit board that engages with the clip of the lead frame and inserts the pin of the lead frame. It is a skewer-shaped building with a multi-story structure.

〔Example〕

An embodiment of the present invention is shown in FIGS. 1 and 2 below. Figure 1 shows the same type of thick-film printed circuit board as in Figure 3, with through-holes formed in the parts to be mated with the clips, and pins of the lead frame inserted into the holes to create a multi-layered structure, and spacers installed between the boards. The structure is such that the above-mentioned internal stress is released by providing a slight gap between the substrates. Here, 3 to 10 are the same parts as in FIG.
Shows hierarchy. 4A is a bent portion of a pin formed integrally with the lead frame 3, and a straight pin is bent by an appropriate method after overlapping the substrates. Although bending is shown here as an example, if the thick film printed wiring board does not move by the time of soldering, appropriate means such as crushing or twisting the pins may be used. FIG. 2 is an enlarged perspective view of the spacer 11. Here, reference numeral 111 denotes the spacer core, and any material may be used as long as it has a small thermal expansion and can withstand soldering of the lead frame. 1
Reference numeral 12 denotes a hole for inserting a pin of the lead frame 3, and there is sufficient clearance between the hole and the pin. Further, 113 is a plate-shaped preform solder, and a hole is made in the same part as 111. 114 more
When the lead frame 3 is soldered to the notch portion formed in the preform solder 113, the solder is properly supplied to each hole. In addition, the core 111 and the preform solder 11
3 is shown assuming a state in which they are simply overlapped, but they may be formed integrally.

As can be seen in FIG. 1, the thickness of the spacer 11 is slightly thicker than the thickness of the conductor and insulator layers formed between the thick film printed circuit boards 1B and 1C or between 1C and 1A, so that they No stress is generated by hitting each other. Further, even if the thick-film printed substrates 1A to 1C have warpage from the beginning, even better results can be obtained if the thickness of the spacer 11 is taken into account. As described above, by stacking the thick film printed circuit boards with spacers in between and bending the pins 4A of the lead frame in this state, a stress-free state can be achieved structurally.

As can be seen from Fig. 2, in this example, the holes for inserting the pins of the lead frame are arranged as an example, but if it is difficult to process the white board due to the pitch, it may be arranged in a staggered arrangement, etc. You can try your best. On the other hand, when soldering the terminals of the lead frame 3 and each thick film printed circuit board, the conventional dipping method has no problem when the number of stacked boards is two, but when the number of stacked boards is three or more, Concerns remain regarding the supply of 1C solder. As an example of a solution to this problem, as shown in FIG. 2, if a plate-shaped preform solder is superimposed on the core 111 and deep soldered, the preform solder is supplied to the through hole of the thick film printed circuit board 1C, and the thick film You can connect pins to through holes on printed circuit boards. Although not clearly shown in the drawings, it is also possible to take measures such as supplying cream solder to each through hole using a dispenser when the thick film printed circuit boards 1C are stacked on top of each other. In the above description, it is assumed that the material of the thick-film printed substrates 1A to 1C is ceramic such as alumina, but a general resin substrate may be used, and there is no restriction on the number of stacked thick-film printed substrates.

[Effect of idea]

As described above, according to the present invention, the current hybrid
As an extension of IC manufacturing technology, we are developing a hybrid multilayer structure for thick-film printed circuit boards, which is generally considered difficult.
IC can be realized. In addition, since there is no technical limit to the number of stacked boards, the packaging density approaches that of the conventional wet build-up method, and in terms of cost, even after subtracting the spacer cost, the mounting density is close to that of the conventional wet build-up method. Compared to the mold cost, significant cost reductions are possible.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is an enlarged perspective view of the spacer shown in FIG. 1, and FIG. 3 is a sectional view showing a conventional example. 1A to 1C...Thick film printed circuit board, 3...Lead frame, 4, 4A...Clip portion of lead frame, 5...Multilayer upper conductor, 6...Insulating glass, 7
... Through hole, 8 ... Surface conductor, 9 ... Back conductor, 10 ... Resistor, 11 ... Spacer.

Claims (1)

[Claims for Utility Model Registration] 1. In a thick-film printed circuit board for forming a dual-in-line hybrid IC, a through hole is provided in the terminal portion to which the lead frame is to be mated, and the through hole is formed integrally with the lead frame or independently. Then, while the spacers and thick-film printed circuit boards are stacked alternately or in a fixed order, and the pins are skewered, solder the terminals of each thick-film printed circuit board, the lead frame, and the pins. A hybrid IC characterized by being formed using 2 The spacer sandwiched between each thick film printed board is
2. The hybrid IC according to claim 1, wherein the hybrid IC is fixed to a pin of a lead frame by a method such as soldering. 3. The hybrid IC according to claim 1 or 2, wherein the thick film printed substrate uses a resin substrate such as glass cloth epoxy instead of ceramics.