flux

How to choose the right soldering flux

A General Overview
Flux is a key contributor to most soldering applications. It is a compound that is used to lift tarnish films from a metals surface, keep the surface clean during the soldering process, and aid in the wetting and spreading action of the solder. There are many different types and brands of flux available on the market; check with the manufacturer or reseller of your flux to ensure that it is appropriate for your application, taking into consideration both the solder being used and the two metals involved in the process. Although there are many types of flux available, each will include two basic parts, chemicals and solvents.
The chemical part includes the active portion, while the solvent is the carrying agent. The flux does not become a part of the soldered joint, but retains the captured oxides and lies inert on the joints finished surface until properly removed. It is usually the solvent that determines the cleaning method required to remove the remaining residue after the soldering is completed. It should be noted that while flux is used to remove the tarnish film from a metals surface, it will not (and should not be expected to) remove paint, grease, varnish, dirt or other types of inert matter. A thorough cleaning of the metals surface is necessary to remove these types of contaminates. This will greatly improve the fluxing efficiency and also aid in the soldering methods and techniques being used.
Detailed Examination
All common untreated metals and metal alloys (including solders) are subject to an environmental attack in which their bare surfaces become covered with a non-metallic film, commonly referred to as tarnish. This tarnish layer consists of oxides, sulfides, carbonates, or other corrosion products and is an effective insulating barrier that will prevent any direct contact with the clean metal surface which lies beneath. When metal parts are joined together by soldering, a metallic continuity is established as a result of the interface between the solder and the surfaces of the two metals. As long as the tarnish layer remains, the solder and metal interface cannot take place, because without being able to make direct contact it is impossible to effectively wet the metals surface with solder.

The surface tarnishes that form on metal are generally not soluble in (and cannot be removed by) most conventional cleaning solvents. They must, therefore be reacted upon chemically in order to be removed. This required chemical reaction is most often accomplished by the use of soldering fluxes. These soldering fluxes will displace the atmospheric gas layer on the metals surface and upon heating will chemically react to remove the tarnish layer from the fluxed metals and maintain the clean metal surface throughout the soldering process.

The chemical reaction that is required will usually be one of two basic types. It can be a reaction where the tarnish and flux combine forming a third compound that is soluble in either the flux or its carrier. An example of this type of reaction takes place between water-white rosin and copper oxides. Water-white rosin, when used as a flux is usually in an isopropyl alcohol carrier and consists mainly of abietic acid and other isomeric diterpene acids that are soluble in several organic solvents. When applied to an oxidized copper surface and heated, the copper oxides will combine with the abietic acid forming a copper abiet (which mixes easily with the unreacted rosin) leaving a clean metallic surface for solder wetting. The hot molten solder displaces the rosin flux and the copper abiet, which can then be removed by conventional cleaning methods.

Another type of reaction is one that causes the tarnish film, or oxidized layer to return to its original metallic state restoring the metals clean surface. An example of this type of reaction takes place when soldering under a blanket of heated hydrogen. At elevated temperatures (the temperature that is required for the intended reaction to take place is unique to each type of base metal) the hydrogen removes the oxides from the surface, forming water and restoring the metallic surface, which the solder will then wet. There are several other variations and combinations that are based on these two types of reactions.

Once the desired chemical reaction has taken place (lifting or dissolving the tarnish layer) the fluxing agent must provide a protective coating on the cleaned metal surface until it is displaced by the molten solder. This is due to the elevated temperatures required for soldering causing the increased likelihood that the metal’s surface may rapidly re-oxidize if not properly coated. Any compound that can be used to create one of the required types of chemical reactions, under the operating conditions necessary for soldering, might be considered for use as a fluxing material. However most organic and inorganic compounds will not hold up under the high temperature conditions that are required for proper soldering. That is why one of the more important considerations is a compounds thermal stability, or its ability to withstand the high temperatures that are required for soldering without burning, breaking down, or evaporating.

When evaluating all of the requirements necessary for a compound to be considered as a fluxing agent, it is important to consider the various soldering methods, techniques and processes available and the wide range of materials and temperatures they may require. A certain flux may perform well on a specific surface using one method of soldering and yet not be at all suitable for that same surface using a different soldering method. When in doubt it never hurts to check with the flux, or solder manufacturer for recommendations.

Purging your Solder Pot – A step-by-step guide

 

Solder Pot 600

Purging Your Solder Pot
There may be times when it will become necessary to remove the existing solder alloy from your solder pot crucible. When this situation arises it is very important for you to remember that you will be handling a very hot molten solder material and you should exercise extreme caution throughout the entire purging process.

Caution: Never attempt this process without using protective shielding devices and heat resistant attire.

Receptacle:
You will need to have a discard receptacle for collecting the solder that is being removed from your solder pot. This can be a reservoir made from aluminum foil that is nested inside a larger container on a blanket of noncombustible material such as sand, vermiculite or clay based kitty litter. Make sure that the receptacle is of a sufficient size to accept all of the solder that is being removed from the solder pot.

Safe Work Area:
The work area, solder pot and discard receptacle that are being used for this process should all have highly visible signs and posted markings warning personnel of the intense heat and the potential for severe burns that may exist. The work surface that you intend to use for this procedure should be smooth, level, and heat resistant. It is also a good idea to have the work surface covered with a protective sheet of noncombustible material in case there are any accidental spills or splashing of the hot molten solder.

In order to help prevent the possibility of any unnecessary accidents you should always limit the number of personnel that are allowed to be within the work area especially during this type of process. To help prevent tripping or restricted movements of your operators you should make sure that the work area is always kept clean, organized and uncluttered.

How to select the correct soldering iron tip: The Important Factors

A guide to choosing the most appropriate tip for your intended soldering application

The soldering iron tip is the part of the iron that is used to transfer heat from the element to the work pieces that are being soldered. The size, composition and configuration of the tip being chosen should be determined by the requirements of the intended application and by the work environment that it will be used in. There could even be rare instances where a custom tip may be desired.

pr6_large

Choosing the correct tip will greatly increase your chances of creating a quality solder joint. It is very important for you to match both the tip and the iron to the soldering application that it will be used on. It is always a good idea to make sure in advance that the desired tips size and configuration are readily available for the type of irons that you have chosen to use. Always remember that a good quality solder joint is rarely achieved by using improper, or inappropriate tools, materials, or equipment.

Technical overview of Solder Pots

Solder Pots provide a method of conduction soldering referred to as dip soldering, that may be used in a wide variety of applications. In dip soldering the solder pot serves as the source of heat and the solder supply. The solder alloy is kept molten in the pot, which maintains the required soldering temperature. The overall heat content of this mass is generally large enough to offset any small heat losses that take place during the dip-soldering application. The pre-fluxed parts are simply dipped into the Solder Pot at the required rate of speed and then withdrawn. The amount of solder that adheres to the assembly is controlled in part by the temperature and by gravity. With this method (assuming the assembly has been properly designed and that the dip-soldering application is correctly performed) a large number of quality and uniformly soldered connections can be made at the same time.

pr4_large

Most of the Solder Pots that are currently being manufactured are heated electrically and there are a wide variety of shapes, sizes and styles that are available. When deciding on the correct Solder Pot to be used, there are some basic considerations that should be taken into account. Some of these include the specific soldering application, the types of materials that will be used, the required temperature range and the acceptable operating tolerance allowed.

How to Properly Care for your Soldering Iron Tip

Proper care and maintenance of your soldering iron tip involves tinning, wiping (and wetting) and also periodic cleaning of the tips shank. These actions are very important and quite simple to perform, but are often neglected. When performed properly they will not only ensure the longest possible working life for your soldering iron tips, but they will also have positive effects on the overall performance of your soldering iron.

 

Tip Care 001

Creating brass models from scratch using resistance soldering

 

 

Bob Connors called up one day and asked if “American Beauty” resistance soldering tools could be used for building a 1/16th scale brass model of a soil finisher. His intent was to use (primarily) 1/4″ Brass bar stock for most of the frame-work and knew that an intense and localized heat would be required for soldering this type of mass together. He needed to be able to heat and solder each joint quickly enough so no previous joints could get hot enough to de-solder. Bob knew this was going to be a real challenge because brass is such an excellent conductor of heat. He sent us a schematic design of the soil finisher and we began to discuss resistance soldering equipment and process recommendations that we felt would work best for his special application.

 

724 001e

 

After our initial discussion regarding the high thermal requirements and the accessibility of the intended solder joints, we agreed the best place to start would be the Model 105H9 High Capacity Probe System, with the addition of the Model 105358 Industrial Pliers-Style Handpiece. This worked out very well and as Bob continued working on this project we had some follow up conversations regarding additional soldering tools that could be added to increase the soldering range and capabilities needed to move forward with this project. This would include items like the Model 105227 Industrial Tweezers-Style Handpiece and the Model 10573 3/16″ Carbon Probe-Style Handpiece  for greater accessibility and attaching smaller component parts. As Bobs new resistance soldering system continued growing to meet his needs his 1/16th scale, highly detailed soil finisher drew ever closer to completion.

 

8005

 

We were excited to receive Photograph updates showing Bobs progress as his soil finisher slowly came to life and are now happy to be able to share this project and the final results with you.

 

P1020308

 

 “American Beauty Resistance Soldering”  and “Your Imagination” The results are infinite.

 

P1020309