![]() It is likely you are going to have to slow the conveyor speed from what you normally use – this will allow temperature settings for the zone to be more achievable.Īdjacent zone in a reflow oven should not exceed typically < 40C, as the two zones will struggle to maintain differentials, this maximum zone delta value may vary oven to oven. Ultimately you will need to perform some thermal profiling, if you are currently using linear ramp profiles you are going to have to make a best guess – otherwise start with a ramp soak spike shaped profile and go from there. Selecting a paste with a generous working window would also help, if you have wildly differing thermal mass components or any temperature sensitive components it will be a challenge. This allows you to drive a good amount of heat into the board in the Ramp, then time to Soak/equalize as best as possible minimizing any temperature differences across the assembly before reflowing. You will most likely need to set up a Ramp-Soak-Spike profile, committing typically Zone 1/2 for Ramp section, Z3,4,5 for soak and Z6/7 for reflow. You are right, given you have 7 zones, you have a fighting chance. My reflow oven has 7 zones though so I think it is possible, any advice would be great. copper on the bottom layer, sounds like a tough challenge. I have a new product coming in and need some ideas on reflow recipe creation. If using a reflow oven recipe generator check that it also considers the convection rate.Seeking Advise for a Solder Reflow Recipe Many reflow ovens employ automated recipe generator software tools to facilitate the development of oven recipes. The pressure is adjusted by the control of the fan speed in each heated plenum. Convection rates are adjusted by setting the pressure in the heated air plenum in each zone. In a convection solder reflow oven convection is the dominant component of heat transfer. Modern reflow ovens used for mass production also have the ability to control convection rate – the speed at which the hot gases hit the product. Solder reflow ovens control the temperature profile by adjustments to the zone temperature set points and the belt speed. Controlling the Solder Reflow Oven Temperature Profile The reflow oven profile will be compared to solder specifications and board/component limitations including: ramp rates, peak temperature, TAL (time above liquidus) and other factors. time data can also be downloaded as a table and can be manipulated by MS Excel or other statistical programs. The measured reflow oven profile is often displayed visually, as a graph, but the raw temperature vs. The profiles can be measured in a loaded or unloaded state by either processing boards ahead of and behind the thermocoupled board to simulate the load or by sending the thermocouple board through alone for an unloaded test. The attached thermocouples can be measured by trailing the wires through the oven while processing or using a recording device that can be passed through the reflow oven by use of an insulating cover. Placing multiple thermocouples in differing locations and on different types of components on the board will give you the most comprehensive understanding of the thermal profile. Best practices for attaching thermocouples also suggest using strain relief to prevent the TC’s from being pulled off the board when the wires are tugged. Aluminum or Kapton tape can be used to attach thermocouples, but is not suggested due to trapped air and loosening of the tape’s adhesive. These thermocouples are attached using solder or epoxy. How to Profile a Solder Reflow OvenĪ solder reflow oven is profiled by attaching thermocouples (TC’s) to the board that is being processed. The difference between the reflow oven set points, or recipe, and the thermal profile is governed by the laws of heat transfer and is affected by mass (weight of the product), surface area, thickness, and the heat capacity (the ability of a material to absorb or give up heat). The temperature settings combined with the belt speed, and the convection rate settings, will produce the thermal profile on the board or product. ![]() The recipe is the temperature settings of the reflow oven in each zone. A thermal profile is a measurement of the temperature, of the product, during thermal processing. The thermal profile is an critical consideration in the solder reflow process. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |