In wave soldering the flux is either sprayed or foamed and applied to the PCB and the total exposure time to soldering temperatures is around 10 seconds. When you reflow a games console or a notebook the time-temperature profile is typically 4 1/2 minutes. A flux designed for wave soldering is really meant for conveyor belt soldering of PCBs and not reworking or reflowing PCBs. Most liquid fluxes would simply evaporate away during the running of a reflow profile, possibly allowing the solder joints to be re-oxidated which would result in early failure due to having low solids content. (around 4% by wt) Our flux has more than 6 times this amount to provide a high solids content flux. Mildly active acids in the flux remove the oxides from the metal surfaces to be soldered. The solids in the flux are responsible for creating an oxygen barrier to prevent the metal surfaces becoming oxidated again at near soldering temperatures.
Our flux is designed to provide not only an oxygen barrier but also a moisture barrier over the soldered areas. BGA failures could be due to: 1. Cracked intermetallic bond.(Thermal cycling) 2. Black pad syndrome (oxidation) 3. Flux residues becoming conductive (moisture) The list can be a lot longer but in our view the above are probably the most important that cause BGA failure. Our flux is the only liquid flux that addresses all the issues that cause early failure of reflowed games consoles and notebooks or whatever else. We are confident that if any flux could single handedly solve the problem of reflowing, than this is the one.
This is a brave statement to make, but that is how excited we are about this flux. We could run tests for the next couple of years to prove our point but feel confident if this doesn’t work, then nothing will and give up on the idea of reflowing and instead just reball or replace the BGA with a new one. This is a test for reflowing. Most console repair shops have given up on the idea of reflowing due to high numbers of failure in a matter of weeks or a few months at best. As they say in the rework industry, a flux can be your best friend or your worst enemy. We think our flux will be your best friend.
The RMA – Rosin Mildly Activated ROL0 Meets IPC-SF-818 Standard for the lowest flux residue corrosivity and highest surface resistance category. Maximum achievable RMA activity to remove metal oxides completely. High solids content to prevent re-oxidation at elevated soldering temperatures. Forms both oxygen and moisture barrier under the BGA. Completely non-corrosive and non-conductive. Our flux starts to activate from about 95 deg C and has a wide temperature window to well above 260 deg C to see through the profile reflowing process to the end with no risk of re-oxidation. No corrosivity or conductivity issues due being a no-clean flux. Some people may find it too tacky but that is a small price to pay since the natural rosin is a very tacky substance but unlike synthetic resins, it stands up to high temperatures and in our opinion the best choice for reliable fluxing.
We recommend the following times and temperatures for your reflow process for all lead-free equipment.
1. Preheat the PCB using the bottom heater of your rework machine from room temperature (25 deg C) to 150 deg C in about 2 minutes. The rate of temperature rise should not exceed 2 deg per second in our view.
2. Soak the PCB for 90 seconds and allow the PCB temperature to rise to 185 deg C at the end of this time. This means that the rate of temperature rise is slowed right down to allow the flux to remove the oxides and even out the PCB temperature, readying it for the reflow process. Use the bottom heater to raise the PCB temperature as much as possible which will reduce the amount of heat applied to the BGA directly, therefore minimising heat related damage to the BGA itself. If the final soak temperature of 185 deg C cannot be reached in the allocated time, then use the top heater as well to assist the bottom heater.
3. Reflowing stage demands that the temperature of the PCB is raised to well over 217 deg C (melting point of lead-free solder) and we suggest 235 deg C as the maximum reflow temperature. The temperature ramp rate should be increased so that the maximum can be reached in 30-45 seconds after the end of the soak stage. Allow a few seconds at the maximum reflow temperature and then switch the top and bottom heaters off.
4. Allow the PCB to cool back to room temperature. If you reflow leaded solder equipment then you may use 205 deg C or 220 deg C as your maximum reflow temperatures. When reflowing PS3 or XBox360, it is important to use anti-warp jigs as both items suffer from PCB warping when heated. Our flux is manufactured for us by a top US flux manufacturer.