Soldering Flux

  • Why is flux important in the soldering process?

    Soldering without flux is similar to brushing your teeth without toothpaste- you can do it but it probably won’t leave you with very pleasant results. Flux plays a crucial role in the soldering process. It spreads onto the soldered metal, keeps the surface clean while the molten solder alloy reaches it, and helps the solder spread over the metal. The application of flux is made easier by using a flux pen, giving you more control of the amount of flux you wish to use.

    This is where the new Kester Select-10 Flux Pen on GoKimco comes in, keeping you smiling all Kester Select-10 Flux Penday long because you enjoy properly melting metals together just like you enjoy your pearly white teeth since you use the best flux- err, toothpaste- every day.

    But first, what is Select-10? This is a zero-halogen, no-clean liquid flux. The makeup of the flux makes it great with challenging applications such as reflowed copper OSP boards or with difficult-to-solder components. It doesn’t spread beyond the spray pattern and it won’t clog the fluxer head. The residues are non-tacky and non-corrosive. This flux has the ability to provide desired hole-fill with preheat temperatures of 135 degrees Celsius with no clogging.

    The Select-10 Flux Pen is an inexpensive addition to your work space that will make a world of difference. Being a no-clean pen, there is no cleanup necessary after its use. The pen provides good solderability under air atmosphere and is compliant to GR-79-CORE, the requirement criteria for its physical design.

    The Select-10 Flux Pen was just added to the GoKimco catalog, so make sure to go check it out! GoKimco is a proud seller of a number of Kester products and we are especially excited about the addition of this one. Kester is a leading global supplier of basic and high-tech attachment materials for the electronic assembly, component and microelectric marketplaces.

  • Gauging Solder Paste Volume

    stencil-printingKnowing just how much solder paste to dispense onto a stencil for a production run can often seem like a guessing game. The ultimate goal is for the paste to completely fill the aperture and release onto the board with 95% transfer efficiency. If the board is not sitting flush again the stencil, then you may see a greater than 100% transfer efficiency. This can lead to a final paste height that is higher than anticipated. Too little solder paste, and you risk not covering the board entirely, leading to an array of problems.

    The amount of paste that you dispense onto the stencil will vary depending on the size of your production run. For a smaller number of boards, ten or under, a minimal amount of paste will be needed to achieve the smooth, rolling action that you need. For larger production cycles, you will want to apply the maximum amount of solder paste possible without loading the squeegee too high, creating flooding and spilling over the sides. A good rule of thumb is 0.75” diameter down the length of the squeegee as a minimum and a 1.5” diameter as a maximum.

    Operators should always be watching for paste leaking out of the sides of the squeegee, which can result in skip defects. Paste remaining idle during the printing process can dry out and harden faster. To prevent this, operators should be trained to open the printer regularly, every 30 minutes is a good rule of thumb, and reposition the paste to the middle of the squeegee.

    It is good practice to print one dummy board before each production run. This first run often uses an excessive amount of flux and can pick up any dust or contamination that can then be loaded into the apertures of the board. Running this test board also ensures that the paste is rolling and that the squeegee is set up properly, with no streaks left behind.

    Using a quality solder paste paired with the right squeegee can make a big different in your product run.

    GoKimco has a complete line of solder paste and quality squeegees to ensure that your production process runs as smoothly as possible.

  • Surface Texture on Solder Joints after Reflow

    surface defects reflowSeeing surface effects when using lead-free solder is not an unusual occurrence. There are many factors that could be causing texture on the solder joints after reflow.

    The following are several of the more common factors that could be contributing to this defect:

    • Thermal profile used, peak temperature and cool down rate
    • Metal finishes on the parts that were soldered, dissolution occurs which can impact color
    • Reflow atmosphere
    • Physical or chemical properties of the flux, some fluxes react more with the solder surface than others
    • Flow properties of the flux during the reflow process, some fluxes flow more rapidly than others, giving extended exposure to oxygen
    • Excessive oxidation of the parts to be soldered
    • Shelf life of the paste or how the paste was handled prior to use

    Keep in mind that while the surface of the board may look frosty, discolored, or be demonstrating shrinkage effects this does not necessarily point to a reliability issue. Instead the solder joint may remain in excellent working condition with adequate intermetallic bonding.

    If you suspect that there may be a reliability issue associated with the appearance you will need to do some pull/shear testing to examine the bond layers. Use a quality pair of shears for the most accurate results. ( If there is a problem with the bond layers, examining the reflow process for problems and / or changing to a different solder paste can correct the problem.

    GoKimco has a wide variety of solder pastes so that you are sure to find one that will sort out this issue. Visit

  • Save on hazmat fees by buying in bulk

    Kimco is always looking for ways to save you the most money on the quality products you or your business needs. We know many of you regularly purchase items from us that must ship via hazmat regulations.


    We are required to charge an additional fee for products that ship as hazmat. This fee is added to any shipping fees incurred. However, the hazmat fee is the same for 1 item as it is for a carton (usually 4, 6, or 12 units) of a particular item.


    For example, if you purchase a carton (4 Gallons) of  Kester 1544 Activated Rosin Liquid Flux, you'd pay the same Hazmat fee as you would for one gallon by itself. Therefore, it is much more economical to purchase hazmat products in carton quantity.


    Hazmat Fee Illustration Hazmat Fee Illustration


    To make it easier for you to take advantage of these savings, we have added carton quantities of many popular hazmat products. And if you are browsing a single product and see this button:


    Buy a Carton

    It will take you to the carton quantity version of the product, where you can easily order the best amount to save you money.
    We appreciate your business and want to help you make the most of every dollar spent with us. Please contact us if you need more information about hazmat fees.
  • Choosing the Best Tools When Soldering with Lead Free Materials

    photoRecent trends in electronics and other areas have suggested that lead free solder is now more popular than lead options. This being said, it is important to first understand why lead free solder may be a more viable and useful option than other soldering methods.

    Lead has long been known to be toxic making it a difficult

    Lead Free

    material to work with. While it can be harmless in some applications, it can be incredibly toxic in other instances. With electronics and other items that we come in contact with every day, it is highly important that the use of toxic materials be limited to protect consumers.

    Lead free solder paste, lead free wire solder, and lead free compatible fluxes are also necessary. The Kester Lead Free solder paste is a great option that is fairly inexpensive. You will also need lead free solder masking agent like the one offered by Chemtronics Chemask.The European Union outlawed the use of lead in consumer goods in 2008 making it essential for users to find an alternative when it comes to soldering. Lead free alternatives are far more available than ever before as more and more people are switching to lead free alternatives. That being said, it may be necessary for users to find new tools in order to work with these lead free materials.

    Choosing something like the Hakko Lead Free solder pot FX301B-03 is a great place to start. Finding a lead free solder pot is the first step to making a successful transition. It is necessary to get a lead free solder pot as it will have different temperature settings, different gauges and more which could make lead free solder unstable and far less suitable for sturdy and durable solders.

    Still another item you may need is of course lead free solder itself. This can either be solder wire like the Kester 24-6337-6401 331 Organic Water Soluble Cored Wire is a great option. These spooled solder wires are great and are easy to use and easy to work with.

    Another option is of course lead free bar solder like the Kester K100LD 04-9574-0050 bar solder. This is also easy to work with and fast for those that do not want to deal with wire spools and unspooling the solder that they need. All of these products can help you quickly switch over to a lead free solder option making your soldering safer and easier all around.

    If you're still not sure what you need for Lead Free Soldering:

    If you have questions about anything related to Lead free soldering, Kimco has the answers you need.  You can browse our website or If you prefer, you can also contact our team of professional customer service representatives for assistance with your needs by calling (800) 521-9197.


  • Why does solder paste need to be stored in a refrigerator?


    Refrigerating solder paste significantly extends the life of the paste. In general, manufacturers recommend storing solder their pastes between 0 and 10 °C (32 – 50 °F), but customers should confirm this with each manufacturer’s specific instructions for storage. The paste should be stored within this range, either in a refrigerator or cold room, as soon as it is received from Kimco Distributing Corp.

    Solder pastes are comprised of flux and powdered solder alloy. (Alternatively, Kimco Distributors also carries flux without powder in it.). The flux in solder paste serves two functions. During the soldering process, it efficiently conducts heat. It also removes impurities, both on the components being soldered and the powdered allow. Thus, even when solder paste is being stored, the flux is reacting with the powder suspended in it.

    These chemical reactions that the flux induces can be slowed by storing the solder paste at cool temperatures. Manufacturers recommend the above range of temperatures, because they have designed solder pastes to not react as quickly at cooler temperatures. Their chemists carefully select compounds that will react quickly at higher temperatures but are fairly dormant at lower temperatures.

    When properly stored, most of the solder pastes Kimco Distributing Corp. carries have a shelf life of approximately six months. (Again, check with each manufacturer’s specifications to confirm this). Once pastes reach room temperature, though, they will quickly expire – some in as little as 24 hours. This is why refrigerating solder paste is so important.

  • Kimco has solutions for Dealing with Component Tombstoning & Wettability


    In the microelectronics assembly and repair industries, wettability can be a major issue. As the size of components decrease, parts become more and more susceptible to the surface tension of solder paste. 01005-sized components are the most problematic pieces to work with, but this affects parts that are 0201, 0402 and 0603 as well. Kimco Distributing carries a full line of Kester solder paste, which helps solve the problem of wettability, but changing the solder paste is not the only solution.

    In an ideal world, parts and pad sizes always match up perfectly. Anyone who has repaired laptops or other electronics, though, knows this is not always true. Wettability can be an issue with any microelectronic work, but it especially comes into play when the component and pad size are not perfect matches. This scenario often results in excess solder paste on the pads, which in turn leads to uneven thermal mass distribution. Ultimately, this causes tombstoning.

    Selecting a different solder paste from Kimco Distributors can overcome wettability issues. In addition to changing solder paste, using a different type of wire is another way to alter the wettability. Kimco Distirbutors has a Kester wire solder for virtually every type of application. Finally, since reflow also contributes to tombstoning, using a different flux is another possible solution. Changing to a Kester flux does not directly solve the wettability issue, but it may be enough to prevent tombstoning, which is often the real issue at hand.

    As you might guess, the solution for tombstoning and wetability requires a unique approach for your specific application. Selecting the right product to meet your specific need might require a quick converstation with one of our customer service representatives. Please feel free to contact us via email or call (800) 521-9197. With over 30 years experience working in the electronic repair and assembly industry, repair and assembly industry, there's no application issue we can't fix.

  • Feature Brand of the Month - Kester Soldering Products


    With over 100 years of manufacturing experience, Kester is a leading global supplier of higher performance interconnecting materials and related services for the electronic and semiconductor assembly markets.Kester has established itself as one of the most respected welding product manufacturers in the industry, and Kimco Distributing is pleased to offer Kester’s products. Because Kester focuses on providing supplies for the micro-electronic and semiconductor assembling industry, their products are among the best available for those purposes. Kimco Distributing Corporation has a full line of Kester’s products. As a primary distributor for Kester Products, Kimco can offer you their quality products at a VERY LOW PRICE plus we stock the items you want for FAST Shipping.

    Kimco Distributing Corp.’s best selling Kester products are their wire solders. Many of the flux-cored wire solders have an instant “wetting behavior,” which makes working with them simple. Because these wire solders spread quickly, they are perfect for fast-paced assembly situations. Businesses often use them in assembly lines, because they are reliable and can be quickly applied. In addition to their viscosity, Kester’s wire solders are compatible with a variety of different metals.

    (Those who know exactly what solder they need are able to search the site by product number. Kimco Distributors has Kester wire solders with product numbers: 2460400027, 2463370010 , 2463370027, 2463376401, 2463376403, 2463376411, 2463378800, 2463378807 and 2470687601.)

    In addition to the Kester wire solder Kimco Distributing carries solid bar solder, flux, flux remover and defoamer. Solid bars of solder are sold by the bar. Customers looking for flux, however, have several sizes to choose from. In addition to these, Kester’s defoamer is available in a 5-gal. container, and their flux remover comes in a 1-gal. size.

    Kester has been around since 1929, when the company transitioned from Chicago Solder Company to Kester, Inc. Few other companies have as long a history as Kester does in the microelectronics industry, and Kimco Distributing is proud to provide their products.

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