JPH01232794A - Soldering - Google Patents

Abstract

PURPOSE:To allow only a predetermined surface of a printed wiring board to be kept at low temperatures even if the soldering temperature is about 260 deg.C by covering the surface of the printed wiring board with a masking material of a predetermined thickness and by soldering the surface of the printed wiring board excluding the masked surface at a predetermined temperature for a predetermined time. CONSTITUTION:After a wiring has been formed by a copper foil 2 on the surface of a printed board 1, an electrode 5 of an electronic component 4 is jointed by a first soldering material with a part of the copper foil wiring 2 on which a solder resist 3 has already been arranged. Then, another electronic component of a different place is temporarily mounted by inserting its leads into throughholes of the printed board 1. At this stage, a mask 10 for covering a part of the electronic component 4 is covered. Further, with this mask 10 covered, the component is brought into contact with a soldering solution 11 in which the solder is melted at 260 deg.C to connect the leads of the electronic component to the copper foil wiring 2 at a second soldering joint. The preferred processing conditions are as follows: 230-270 deg.C, 3-7 seconds, and 2.0cm or more for both horizontal thickness H1 and vertical thickness H2 of the mask 10.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a technology for assembling printed circuit boards constituting electronic equipment, and in particular, to assembling technology for assembling printed circuit boards constituting electronic devices, and in particular, assembly of leads or electrodes of components mounted on the printed wiring board and conductive lands on the surface of the printed wiring board. This relates to a second soldering method using the dip method.

Conventional technology Conventionally, a component is placed on the top surface of a printed wiring board, and its lined part is passed through a hole and brought into contact with the molten solder surface together with the bottom surface of the printed wiring board. I have been making solder joints. In addition, as an applied method, in order to prevent solder from forming on the entire surface conductor of a printed wiring board, a resin called solider resist is printed with a thickness in the range of 15 ± 5 μm at a time, and solder does not adhere to the printed portion of this resin. Non-forming methods have also been used.

Problems to be Solved by the Invention In such a conventional configuration, unnecessary and harmful heating is performed on the exposed resin surface of the printed wiring board or the printed portion of the solder resist due to solder contact. In addition, the continuous heat resistance temperature limit of paper-based phenolic resin laminates and epoxy glass laminates, which are often used as printed wiring boards, is said to be approximately 150°C, but in reality, the temperature limit for contact with soldering temperatures of 260°C is As a result, overheating of over 150°C has occurred. As a result, the laminate and XJpI73 that make up the printed wiring board are burnt and bulged.Furthermore, the bottom surface of the printed wiring board has already been soldered manually.

When a surface layer of tin/lead-based low-temperature solder is present, dip solder is sometimes printed on solder resist to contact the part where a component with an electrode is bonded to the surface layer. There were some things that weren't there.

The purpose of the present invention is to eliminate these problems,
In particular, the aim is to realize a process in which only a predetermined surface of a printed wiring board can be maintained at a low temperature even when the soldering temperature is about 260°C.

Means for Solving the Problems The present invention covers the printed wiring board surface with a mask material having a thickness of two or more fences, and covers the printed wiring board surface outside the mask,
Under processing conditions of 230°C to 270'C, 3 seconds to 7 seconds,
This is a soldering method that includes a soldering process.

According to the present invention, since the mask material has a thickness of 2 uu++ or more, the soldering process under the above processing conditions),
2 degrees, the temperature inside the printed wiring board covered with this mask material is maintained at 150 degrees Celsius or less.

Example Next, the present invention will be described in detail by way of examples.

The drawings are schematic cross-sectional views for explaining the steps of an embodiment of the present invention. In this embodiment, after forming wiring with copper foil 2 on the surface of a printed circuit board 1 whose base material is a paper-based phenolic resin laminate, a solder resist 3 is placed in advance, and
An electrode 5 of an electronic component 4 is bonded to a portion of the copper foil wiring 2 using a first solder material 6. Next, another electronic component 8 is temporarily attached to the same printed wiring board 1 at another location on the same printed wiring board by inserting its lead 9 into the through hole 7 of the printed wiring board 1. At this stage, in preparation for soldering in the next step, a mask tO is placed over some of the electronic components 4. Then, with this mask 10 still on, it is brought into contact with a solder liquid 11 melted at 260° C., and the leads 9 of the electronic component 8 and the copper foil wiring 2 are connected at the second solder joint 12. According to experience, the appropriate treatment conditions are 230°C to 270°C for 3 seconds to 7 seconds, preferably 260°C±10°C.

The time was 5 seconds±1 second.

When a resin material is used as the mask 10, heat conduction is relatively low, but solder heat is easily transmitted with a normal film thickness. As a result of experiments, when using relatively inexpensive thick resin materials such as phenol and epoxy,
It has been found that in order to satisfy the requirement that the solder temperature transmission at 260° is 150°C or less, it is effective to have a horizontal thickness I (and a thickness H2 of 2.0 or more in the thickness direction). .

Printed wiring board (size 10
The table shows the case where the temperature of the bottom surface of No. 10 is 1.4 m and the sample is passed through the Flora solder bath at a conveyor speed of z minutes. The temperature measurement point is the position of the solder joint 6 of the internal electronic component 4.

(Margin below) Effects of the Invention As described above, according to the present invention, it is possible to maintain the surface temperature of the printed wiring board at 150°C or less, and the above-mentioned three drawbacks of the conventional method can be solved. . Polyimide, polyolefin, aramid, Teflon, etc. can also be used as mask materials, although they are expensive.

[Brief explanation of the drawing]

The drawings are sectional views of essential parts for explaining embodiments of the present invention. ■...Printed circuit board, 2...Copper foil conductor, 3...Tsuruda Regis I, 4...Electronic components, 5...Electronic Electrodes of parts, 6...
・Solder (joint part), 7...Through hole, 8...
...Other electronic components, 9...Leads, 10...
... Resin mask, 11 ... Solder liquid, 12
...Solder joint. Name of agent Patent attorney Toshio Nakao 1 person 1 hour -- Thickness in the plane direction of the mask H2 - 1 between all rectangular sides of the mask:!

Claims (1)

[Claims] After soldering the electronic components to the printed wiring board in advance, cover the electronic components and the soldered parts to a thickness of 2.
A soldering method comprising the steps of covering the printed wiring board surface with a mask material having a thickness of mm or more and performing soldering under processing conditions of 230° C. to 270° C. and 3 seconds to 7 seconds.