JPH02174189A - Method of placing leadless component onto conductor-pattern support substrate and assembly of conductor-pattern support substrate and leadless component - Google Patents

Abstract

PURPOSE: To remove a solvent between the constitution part and the base by holding the constitution part on the base at a specific position with a pad of an adhesive material, connecting the connector and pad of the constitution part to a connector and a pattern on the base by bridges of solder, and isolating the constitution part and the base from each other. CONSTITUTION: Respective connection pads 2 of the base which supports printed wires are given solder 3 at specific height in advance, and an adhesive material 4 is placed on the base 1; and a leadless constitution part 5 is positioned thereupon, and a connection pad 6 given a specific amount of solder 7 at its side part is placed in contact with the solder 3. Then those solder parts 3 and 7 are fused to connect the pads 6 and 2 by a bridge 8, and the interval X between the constitution part 5 and base pad 2 is made relatively large so as to facilitate cleaning in the space around the constitution part 5 and base pad 2. Consequently, any solvent having entered the gap can easily be removed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a surface mounting leadless components on a substrate supporting conductors, patterns, such as, for example, so-called printed wiring.

Solder cream (a mixture of solder particles, solvent, emollients, and flow components) is applied to the connection pads of a printed wiring component and acts to lightly adhere the component to the connection pads. Add the cream (
placing the assembly in a protected state (warmed in an oven to dry) and then subjecting the assembly to a general solder reflow method (by any means, i.e., by hot gas, vapor phase, infrared radiation, or thermal conduction); That melts the solder in the solder cream and ultimately secures the component in place.

The main problem with the technique described above is that it leaves only a very small gap between the component and the interconnect substrate, perhaps on the order of 1 to 3 thousandths of 11n.

The solvent is drawn into this gap by capillary action, so
It would be extremely difficult if it were impossible to clean in that case, i.e. if the solvent was left to leak out after manufacturing, it would probably affect the flint wiring patterns and components. and corrodes the connections to the assembly. Moreover, the thermal contact between the components and the substrate deteriorates and stresses occur due to the different heating rates of the components and the substrate during use of the manufactured item, and in any case the partial Protected solder cream does not adhere strongly and is not sufficient to keep components in place during the wiring process prior to solder reflow methods, after fi, and during use. For wiring that is subject to extremely strong shock loads and acceleration, especially if the component pads are conductors,
Attachment of the components to the base solely by soldering to the pattern is not complete.

According to one aspect of the invention, the component is held in place on the base by a pad of adhesive material between the component and the base, a connector for the leadless component;
The pads are then connected to connectors and patterns on the board by solder posts, such that there is a relatively large separation between the component and the board to facilitate cleaning of the space around the component and the board pad. and a method for placing a leadless, pattern on a conductor, pattern supporting substrate, characterized in that the connector, pad of the leadless component is then connected to the conductor, pattern on the substrate by a pillar of solder. is provided.

According to a second aspect of the invention, the component is secured to the base by adhesive pads between the component and the base and by solder posts between the adhesive pads of the component and the contactors, patterns on the base. An assembly of a conductor, a pattern support base, and a leadless component is provided.

In order to better understand the invention, one embodiment will be described below with reference to the drawings.

FIG. 1 shows a ceramic substrate 1 supporting a printed wiring including connection pads 2 of the components. Each pad 2
The solder 3 is pre-soldered to a roughly constant known height by the solder 3, e.g. Redpoint
A flexible, thermally conductive adhesive material (metallic bonding material) 4, such as Elastathern®, is placed on the substrate 1, a leadless, chip support 5 is placed on the adhesive pad, The connection pad 6 is brought into contact with the solder 3.

The chip support 5 is of the usual type and has connection pads 6 L-shaped extending down the sides of the support and then onto its underside. Prior to positioning the support on the base, the sides of the connection pads 6 are applied with a predetermined amount of solder 7. The assembly shown in FIG. 1 then stabilizes the adhesive 4 and firmly attaches the chip support 5 to the base IB.
1. Placed in the oven to stabilize for attachment. A solvent, such as liquid Rosin, is then applied to the assembly, which is then reflowed and soldered.

This causes solder 3 and 7 to melt, allowing solder 7 to flow down the side of pad 6 and blend with solder 3, with the result that each post or bridge 8, as shown in FIG. This is the connection to pad 2.

For reflow soldering, vapor phase methods are preferred because they provide an inert, relatively oxygen-free atmosphere to the molten solder, and it also tends to reduce the surface tension of the molten solder, reducing its This improves the ability of the solder 7 to flow downwardly and toward the bottom surface of the chip support 5.

Applying solder onto the pad 2 involves applying a predetermined amount of solder cream, for example by screen printing.
Alternatively, it can be carried out by placing it automatically or by a manual dispenser, drying it and then reflowing the cream to effect the removal of the solvent. The chip support 5 can be cleaned and dabbed with solder, which gives a fine surface coating of solder on the connection pads 6 and then coated with a cream of solder to prepare a layer 7 of solder. A pattern is screen printed onto a non-wetted surface, such as the surface of a bare ceramic substrate (not shown), and the pattern matches the pattern of the pads on the support 5, of course. The solder cream is positioned on this base in such a way that the solder cream is dried and then reflowed, just as the support is connected to the base by known manufacturing methods. As a result, the solder pad 6 is overlaid with cream. During the reflow process, it is advisable to apply a gentle downward force, for example by applying a small weight, to the anyway relatively light components, which causes said components to float above the molten solder. prevent this from happening.

The component is then freed of solvent.

Another method, apart from the above-mentioned method, for providing the solder joints 7 may be for a solder cream to be applied directly onto the connection pads 6, for example by using a dropper.

In the completed assembly shown in FIG. 2, the length X of the gap between the substrate 1 and the chip support 5 around the adhesive pad is relatively large 6, e.g. is 0.0
It is between 0.03 and 0.025 inches.

Preferably, it is about 0,005 in. or more,
Alternatively, it may be about 0.010 inches or more, or about 0.015 inches or more, so that any solvent that gets into this gap is unlikely to damage any wiring components. It can be easily removed by the cleaning method described above.

Meanwhile, it not only improves the thermal contact between the chip support 5 and the substrate 1, but also helps the chip support hold in place during assembly processing before shaping the solder bridges, and also improves the Satisfactory electrical contact is provided by the solder bridges 8 and the adhesive pads 4 to ensure that during use of the assembled assembly a particular adhesion of the chip support to the base occurs. At the same time, the adhesive nature of the pad 4 is relatively flexible, allowing it to accommodate any differential changes in the dimensions of the chip support and substrate due to temperature.

A protective coating, a so-called conformal coating, can be applied to the completed circuit, which covers each post joint due to the relatively large separation between the chip support and the substrate. 8, thus providing improved perimeter protection for the circuit.

As well as the chip support, other components, e.g. chips,
Capacitors and resistors, also tantalum.

A capacitor can be attached by the method shown.

In the case of certain components, especially tantalum, capacitors, for example, the component is submerged in a wave of solder to obtain a good solder coverage, and then the component is immediately dabbed downward onto a hot plate. Solder the terminations of the components in one motion by applying a shock and forcing some of the still molten solder downward toward near the bottom of the terminations while simultaneously flattening the underside of the terminations. It has been discovered that it is better to do this.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the electrical components of the dress mounted on a printed wiring board, and FIG. 2 is a similar cross-sectional view after the assembly has been soldered by reflow. In the figure, 1... Ceramic base; 2, 6...
...Pad; 3.7...Solder; 4...
・Adhesive material; 5...Leadless, chip support:
8...Solder bridge. 2nd page of purification i1 (no change in content) 1. Indication of the case 1988 Patent application No. 311049 Relationship to the case Patent applicant address Tabulus-Cii 2, London, Aegiri
・N, 5.7 A.T., Strand, 11 Name Pretty/Yu, Nearos is Chair, Public. Haru Company 4 Limited, Agent 105 Address Bussan To Noshi Annex, 1-15 Nishi-Shinbashi, Minato-ku, Tokyo Telephone (591) 0261+l) Request
Homare (2) Drawings (3) Contents of amendment to power of attorney

Claims (1)

[Claims] 1. Connectors for leadless components, wherein the component is held in place on the base by a pad of adhesive material between the component and the base. The pads are then connected to the connector on the board by solder bridges. connectors for leadless components; and connectors for leadless components. The pads are then connected to the conductors on the board by solder bridges. A conductor characterized by being connected to a pattern. Leadless on pattern support base. Method of placing the pattern 2. The components are connected by adhesive pads between the components and the substrate, and by the connection pads on the components and conductors on the substrate. A conductor characterized in that it is fixed to a base by a solder bridge between it and the pattern. Assembly of pattern support base and leadless components.