Solder Paste FAQs

solder paste faq
When should I use a flux pen?

Dispensing flux into confined areas can be problematic. Use of a flux dispensing pen helps to solve this problem because the flux pen works like a marking pen, dispensing just the right amount of flux where needed. After a certain number of applications, the felt tip starts to wear down, so replacement tips are available.  For better dispensing control, consider using a tacky flux instead of an alcohol based flux.


What is the best way to store flammable chemicals?

Generally, flammable chemicals be stored at room temperature with normal humidity, unless otherwise specified. Flammable materials should also be stored in an approved flammable materials storage cabinet. Special care is required when storing flammable chemicals at elevated temperatures, especially alcohol and other chemical compounds that can expand when heated, which could create explosive pressure within the container.


How are pin holes formed?

Pin holes are formed by moisture that is trapped within or beneath the solder. When the moisture comes into contact with the component-lead, solder paste, through-hole, wire or material under elevated temperatures, the water can begin to boil, causing pin holes to be formed by trapped or escaping water vapor.


Why is 2% silver sometimes beneficial?

When soldering silver or silver-plated component leads, adding a small amount of silver (typically 2%) to the solder helps prevent the silver found on the component lead from migrating onto the solder, which can result in a weak or brittle solder connection.


What is the ideal size for syringable solder paste?

AMTECH offers 100 grams of paste in a standard 30cc syringe, as well as 35 grams of paste in a standard 10cc syringe.  A 30-guage needle is the smallest size recommended for dispensing SMT solder paste (Type 6 powder).  Plungers and needles are available upon request.


When is Sn60 recommended over Sn63?

Sn60Pb40 solder paste has a plastic range that allows it to lay down a slightly thicker coating of solder than Sn63Pb37, which is often preferred for lead tinning or similar applications. By contrast, Sn63Pb37 solder is eutectic, with no plastic range, and generally flows better than Sn60Pb40, making it the preferred solder paste solution for surface mount and wave soldering applications.


Do I need to remove rosin flux?

Under normal circumstances, rosin flux residues are non-conductive and non-corrosive and thus do not have to be removed from a printed circuit assembly, except perhaps for aesthetic reasons. However, in situations where the working temperature of the PCB exceeds 200°F, rosin flux residues can melt and become conductive. In such instances, the rosin flux needs to be removed.


How is dross created?

Dross is generated by a combination of heat and agitation that caused oxides to form in various solders. As the solder pot gets hotter, and with increased agitation, the faster the dross gets generated. Dross formation can be reduced or eliminated by the use of nitrogen, which prevents oxygen form reacting with the outer surface of the solder. Dross reducing agents can also be used to minimize tin and lead oxides by releasing oxygen into the air. When using dross-reducing gents, be careful to follow the instructions on the product data sheet and SDS, where applicable.


Can I solder to aluminum?

AMTECH dose not offer any solder products that can be used for soldering to aluminum.


Why are thermocouple wire materials not solderable?

A thermocouple works by measuring the change in resistance of two dissimilar metals joined in a welded bead. If you were to join the two metals with solder, the thermocouple would provide meaningless numbers. In some cases it is possible to surround or encapsulate a thermocouple wire without forming a metallurgical bond. To fix a broken thermocouple, you can attempt to re-weld the thermocouple bead. When attaching a thermocouple to a PCB for reflow profiling, you generally have two choices: utilizing a high temperature alloy to encapsulate the thermocouple; or using a cyan-acrylate adhesive product to attach the thermocouple to the PCB.


How do you properly dispose of processing chemicals?

Chemical disposal regulations vary form state to state and from country to country. We suggest that you contact your local EPA office to verify that proper disposal requirements are being followed. An EPA representative can also recommend qualified hazardous waste handlers in your area. Prepare in advance by having copies of all relevant product data sheets and Safety Data Sheets (SDS) available for review by a certified hazardous waste disposal expert.


What are the normal temperature ranges of the alloys available for AMTECH?

See Alloy Temperature Chart


Gold color is appearing on the surface of the solder pot?

When molten solder is exposed to air it can oxidize and create dross, which can appear as gold or a purple-blue in color. Formation of tin oxide is normal and generally does not degrade the reliability of the solder. This discoloration can be prevented by the use of a dross inhibitor, which is generally available as an anti-oxidant powder or pellet.


What is the standard ratio of flux to metal in a solder paste?

The typical solder paste formula consists of 90% metal and 10% flux by weight, and 45% metal and 55% flux by volume.









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