JPH0231627B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a desoldering device used to absorb solder melted by heating by capillary attraction when it is desired to break a solder joint in an electronic circuit, for example.

Desoldering wicks in elongated form are well known, as shown for example in US Pat. No. 3,627,191 and my US Pat. Nos. 4,081,575 and 4,164,606. Such wicks are assembled together (and then flattened) into elongated cylindrical structures and then covered with thin copper (or It consists of strands (alloy coated). In use, one end of the formulated wick is applied to molten solder, which is absorbed by capillary attraction into the interstices between the strands.

In fact, the gap between adjacent strands of bare wire is
It is recognized that it is relatively small. The primary gap is the volume within the cylindrical (but flattened) structure, but molten solder can only fill this space by passing between adjacent strands of braided strands. The solder flow is slow because the volume can be reached. In fact, when carrying out a desoldering operation, the complete braid is broken at the end of the wick by "wiping" with the tip of the soldering iron over the wire ends protruding into the desoldering position, resulting in Spread the wire into a fan shape at the end,
It always happens that a widening gap is created.

According to the invention, the strand consists of at least one strand and is formed by weaving, roping, knitting, stockinette knitting, or crocheting, and at least the surface of the strand is metallic and highly receptive to solder flux. In fact, a desoldering device is provided which consists of an open mesh structure coated with a solder flux that facilitates wetting by molten solder. Furthermore, the present invention provides a method of desoldering using a device consisting of an open mesh structure consisting of at least one strand and formed by weaving, roping, knitting, stockinette knitting or crocheting. be done.

A relatively large gap size for solder absorption is advantageous because adjacent portions of the strands or strands are touching or not touching each other.

The preferred structure consists of an elongated, flat, tubular structure formed by stockinette knitting. In this way, a single strand is formed into an elongated cylindrical structure by continuously operating a stockinette knitting machine, which structure is subsequently formed (by passing between rollers or
or simply wound onto a reel) and flattened.

The open mesh structure exhibits the advantage of relatively large sized gaps for receiving molten solder. More solder is absorbed by the same amount of copper strands, with improved efficiency and economy. The stockinette knitting process makes it possible to build wicks of at least equal length within a given time interval and also makes it possible to form wicks of greater width. The wick may also be formed as a pad instead of an elongated structure, in which case it would be applied against the circuit board to remove molten solder from the entire area of the circuit board.

Open mesh has additional advantages. The twisted copper strands must be cleaned of oxide layers and other contaminants that would prevent them from accepting solder flux or being wetted by molten solder. For cleaning, place the wick in a vacuum,
Alternatively, it may be carried out by heating in a reducing gas or in an inert gas. However, because the prior art adjacent strand-contact composition structure does not readily allow gas to pass from or into the interior of the cylindrical structure, its inner surface will not be as clean as the outer surface. However, the inner surface is important as the wetted surface. Although chemical cleaning may be used if appropriate, the contacting strands in prior art composition structures inhibit the passage of cleaning fluid into and out of the composition interior. Cleaning chemicals trapped inside the braid would require extensive rinsing to remove it, or it would become a significant contaminant.
By comparison, the open structure according to the present invention
easily by heating in a vacuum or in an inert or reducing gas (e.g. by passing an electric current through the wick until it becomes red hot) or by using a chemical cleaning agent followed by rinsing. make it easier to wash. Due to the low weight of copper, less energy is required for resistive heating.

Additionally, prior art composed wicks are typically coated with flux by immersion in a solution containing rosin, followed by evaporation and drying.
The solution must penetrate the inner surface of the wick, but in prior art wick compositions, that penetration will be slow and incomplete. The open mesh construction allows the solution to rapidly access all surfaces of the strands, allowing subsequent drying by application of hot air or by placing the wick in a vacuum.

Additionally, it is possible to coat the strands with copper (or an alloy as in my U.S. Pat. No. 4,164,606) after the open mesh structure has been formed, thus covering all surfaces of the strands. A clean copper coating is obtained. for example,
The structure may be formed from bare copper wires coated with copper by chemical deposition, or from low-cost bare metal wires coated with copper (or of truly non-metallic filaments). Good too. A flux is then applied to it.

Because the open mesh structure of the present invention has a lower copper content per unit length, it may also require a lower wattage soldering iron for heating than the structured wicks of the prior art. It will be recognized.

An embodiment of the present invention will be described with reference to the accompanying drawings.

Referring first to FIG. 1, the prior art constructed wick consists of parallel, contacting copper strands 10, 12 which are constructed together into a cylindrical structure and flattened. The wick end 13 is shown fanned out (as described above) to improve the size of the clearance for desoldering. Referring now to FIG. 2, the stockinette wick according to the invention consists of a strand 20 of copper formed into a tubular open mesh structure by a continuous spiral forming stockinette machine and subsequently flattened. Although the wick is shown formed by knitting the strands into loops, if the adjacent strands do not touch and have an open space to absorb the molten solder, the wick may instead be made of cloth. The open mesh structure may be formed by knitting or, where appropriate,
It may be formed by weaving or composition. After cleaning, the strands 20 are coated with flux to complete the wick. As mentioned above, the copper strands (copper,
Alternatively, it may be coated with tin or a low melting point alloy such as a tin-lead alloy. And, indeed, the strands may consist of low cost metal or non-metallic filaments that are coated with one of the metals mentioned above prior to flux coating. Instead of the elongated shape shown, the wick may also be formed in the shape of a pad.

In stockinette constructions as shown in Figure 2, the diameter of the strands is in the range of 0.1 mm to 0.25 mm. With a diameter below 0.1 mm, the stockinette knitting process will be too slow and there is a risk of breaking the strands, and with a diameter above 0.25 mm, the mechanical wear on the stockinette machine will be too great. However, the range of diameters varies depending on the type of stockinette knitting machine. In any event, stockinette knitting machines produce, for example, cylindrical structures with a diameter of about 2 mm to 25 mm or more, which tubes are flattened between rollers. The size of the needle mesh or mesh is determined by the selected diameter and the number of machine needles arranged around it, thus 2, 3, 4, 6, 8 or 12 or more needles can be knitted. and this will be the number of stitches per circumference. The larger the number of needles for a given diameter, the greater the number of stitches per unit length and the smaller the mesh size. In the example shown in Figure 2, the strands are copper strands with a diameter of 0.1 mm, and the manufacturing speed is 1
It was 130m per hour.

Stockinette knitting can be performed with all types of yarns, including cotton, wool, silk, nylon, acrylic, plastic, and metal. If it is metal, it must be flexible, such as copper. Stockinette knitting of metals is substantially the same as stockinette knitting of textiles or similar yarns by selecting appropriate operating parameters, since metals tend to suffer greater wear during machine processing. According to the necessary metal threads, a knitted wick would of course require subsequent metallization.

[Brief explanation of drawings]

FIG. 1 is a detailed elevational view of one end of a prior art composite wick, and FIG. 2 is a detailed elevational view of a knitted knitted wick according to the present invention. DESCRIPTION OF SYMBOLS 10, 12... Parallel contact copper wire group, 13... End of wick body, 20... Strand.

Claims (1)

[Scope of Claims] 1 Consists of a strand having at least a metallic surface, receptive to solder flux, and coated with a solder flux that makes it easily wettable by molten solder, said strand being knitted or woven. an open mesh structure is provided by forming, stitching, composition, or cross-knitting, and the open mesh structure includes adjacent portions of the strands or strands of which the open mesh structure consists of substantially the entire length of each other. A desoldering device characterized by forming a relatively large gap that is effective for absorbing solder with almost no contact between the solder and the solder. 2. The desoldering device according to claim 1, characterized by an elongated, flat cylindrical structure. 3. The desoldering device according to claim 1, characterized by a pad-shaped structure. 4. Desoldering device according to any one of the preceding claims, characterized in that the strands are copper-coated after being formed into the open mesh structure and before receiving the flux. 5. A desoldering device according to claim 4, characterized in that the strands are made of non-metallic filaments. 6. The method according to claim 1, 2 or 3, wherein the strands are coated with an alloy after being formed into the open mesh structure and before receiving the flux. Desoldering equipment.