ALPHA® CL-78 is a no-clean, dispensable solder paste compatible with the Alpha UP-78 series of modern, no-clean pastes. It is designed for high speed automated or manual dispensing through a wide range of needle sizes. The post reflow residues are clear and colorless.
Formulated for both slow and high speed dispensing with manual, time/pressure machines and automatic, positive displacement equipment. This soldering paste will provide universal results for component attachment, prototype building, BGA attachment, general rework, paste-in-hole application and deposition in deep cavities.
Available as a Type 5, Alloy 62/36/2 25g Dispensing Syringe.
Key Products Features & Benefits:
Prod. No. 111323
Alpha CL78 62/36/2 10cc Syringe
Health & Safety
Q - What particle size are the dispense grade pastes?
A - Generally type 3 for basic applications but more often popular are type 4, 4.5 and 5. The major factor in the selection of a dispense grade paste can be the flux content which is controlled by the lower than normal metal content.
Q - What alloys do they come in?
A - There is no reason why they can't be made in any alloy so long as it is commercially viable to do so. Minimum production quantity for a batch of dispense grade paste is 4 Kg. Dispense grade paste typically has a metal content of 83.5% to allow for the extra fluidity needed.
Q - Is there a recommended needle size that works well with these products?
A - The general rule of thumb is to allow seven times the largest particle size as the minimum internal diameter of the needle for a repeatable process. Some engineers will insist on 8 times.
Q - Do they reflow at the same temperatures as printable pastes?
A - On an alloy by alloy basis the reflow temperature will be the same.
Q - They appear to be more suitable to machine dispense, can l apply manually?
A - Yes, although not as repeatedly. Generally solder paste dispensing is more successful in a positive displacement pumping system as opposed to an air displacement system which will give differing volumes of paste per shot as the volume of solder paste in the syringe decreases. Solder paste is compressible whereas an epoxy glue is not.
Q - When should l use a flux gel in preference to a solder paste?
A - Industry trend is to try a flux gel first for rework applications or a preform where additional solder volume is required with a printing process.
Q - Can the flux gel be safely left on the board without cleaning?
A - Provided the minimum amount possible has been used and the affected area has all been brought to reflow temperature then the flux gel residues produced should be the same as those from a standard printing / reflow process.
Q - What size syringe sizes are currently available?
A - 10cc & 30 cc EFD tend to be the most popular.
Q - Do these products dispense well enough to link to an automatic system?
A - In the case of the type 4.5 and type 5 OM338T above then the answer is yes. The same type of flux gel can be used to condition the pump head in the machine prior to and also in cleaning down the machine after solder paste dispensing operations.
Q - What is colophony and can it cause any health issues?
A - Colophony is a generic term for rosin, this is the sap or sticky substance that derives from pine and spruce trees. Its "stickiness" lends itself to being used in a wide range of products. We have traditionally used this product in fluxes due to these specific properties it can however lead to breathing difficulties and skin sensitivity. Always use fume filtration when soldering and change filters regularly.
Q - What is the difference between rosins and resins?
A - The terms are often used interchangeably, but rosin is a naturally occurring substance, and resin is either a modified rosin or completely synthetic material. Rosins are plant based products and are subject to more natural variation than resins, however resins are commonly used in newer flux formulations due to their more consistent performance.
Q - Do I need to change my printing process when I go to finer printing from size 3 to size 4 paste?
A - Generally when changing from T3 to T4 there is not much difference in printing setup. Depending upon the paste used you may have to make slight adjustments to print parameters such as release speed as aperture fill is greater with finer powders on small apertures but this is just to optimise the print as you would do when changing any paste. It’s by no means certain you will need to do this but it may give you further benefits.
Q - Do I need to change my printing process when I go to Ultra Fine printing from size 4 to size 5 paste?
A - The biggest change will be going to PS5 and its not so much the printing parameters changing but the stencils are invariably a lot thinner and so you need good support and setup such as making sure you have a release distance of 3 mm set (the distance over which release speed is controlled as the stencil acts more like a drum skin) I would also run with the minimum pressure to avoid stencil damage (coining) this is as most PS stencils are <100µm typically 75µm in thickness. It’s not as bad with PS4 as most stencils are in the 100µm or slightly above range and are more robust.
In all cases (can’t really think of an exception) smaller powder sizes go hand in hand with printing smaller features. Smaller features as we approach Area Ratio 0.66 and in some cases people try to/do operate in the region of AR 0.6-0.66 mean that the printing process has to be good, you have to “respect the fundamentals” i.e. board support, calibration of such things as print height, squeegee condition, decent PCB quality, registration etc.
Again more a feature of small apertures rather than the powder size of paste itself you may need to look at what is your maximum ‘abandon’ time with any paste if you run a start stop process and work to it i.e. don’t exceed and use automatic under screen cleaning where needed. Smaller apertures tend to ‘clog’ more readily and so may need a more frequent aperture clean regime.