Patent Application
20090124131
The present disclosure relates to methods and adapters for mechanically and electrically connecting thermocouples to data loggers.
Conveyor ovens (also called furnaces) are used in a variety of industries including the electronics, baking, and painting industries. Generally, conveyor ovens have multiple heating zones and may have one or more cooling zones through which product is conveyed. The heating zones are thermally isolated from each other by air curtains or other means. Such thermal isolation allows each zone to be maintained at a temperature that differs from other zones in the oven. A particular advantage of conveyor ovens with multiple heating zones is that products can be heated to different temperatures at different times and rates as they pass through the oven.
In the electronics industry, conveyor ovens, known as reflow ovens, are used to electrically bond electronic components to printed circuit boards (PCBs) with solder paste. Typically, the soldering process within a conveyor oven can be characterized by the following phases: preheat or ramp phase, the dwell or soak phase, the reflow or spike phase and the cooling phase. In the preheat phase, the solder paste is heated from room temperature to a preheat temperature to promote evaporation of the solvents, or carriers, in the solder paste. During the soak phase, the solder paste is permitted to “soak” for a predetermined period of time at a temperature range at which the flux, the active ingredient in the solder paste, becomes active. In the reflow phase, the solder paste is heated above the liquidous, or melting temperature of the solder for a predetermined period of time sufficient to permit reflow (i.e., melting or wetting) of the solder paste. In the cooling phase, the solder joint solidifies, thereby electrically bonding the components to the circuit board.
Typically, the thermal requirements for a solder paste (also called solder paste specifications) for preheat, soak and reflow phases are specified by the manufacturer of the paste. Generally speaking, “profiling” is the process of determining the process settings for the oven that will best satisfy the thermal requirements of the solder paste without damaging the electronic components. Such process settings may include, for example, the temperature settings of each oven zone and the oven conveyor speed.
Devices for measuring the temperature profile of a product conveyed through an oven (i.e., the temperature response of the product) are known. For example, electronic data loggers (also called data collectors or monitors) have been developed that attach thermocouple sensors to a test PCB. One such data logger, the M.O.L.E.® temperature profiler, is an oven profiler sold commercially by Electronic Controls Design, Inc., of Milwaukie, Oreg. Beyond the M.O.L.E.®, the test PCB has various thermocouples strategically placed thereon. Traditionally, each thermocouple is connected directly to the electronic data logger. The electronic data logger is physically spaced apart from the PCB so as not to affect the heating of the PCB and thereby cause inaccurate temperature profiling. The data logger stores temperature information measured by the thermocouples and that information can be processed to determine and control the optimal temperature profile of the product.
Once the data logger has passed through the oven, the collected data is downloaded to a computer using a special docking station, or via RF or cable. A software package located on the computer graphically illustrates a temperature profile of the collected data and provides a comparison to an optimal profile. The operator estimates changes to the oven settings for reducing the difference between the temperature response of the assembly and the desired thermal profile to within an allowable tolerance. The operator adjusts the oven settings and repeats the process until the appropriate thermal requirements for the solder paste are reached.
If several thermocouples are used, however, the thermocouples can quickly become tangled and difficult to organize. Additionally, it is difficult to coordinate into which data logger slots the thermocouples should be plugged. Even further, there is increasing commercial pressure to process smaller parts that require more temperature sensors to obtain a proper temperature profile. Ovens are also decreasing in size, forcing data loggers to become smaller. With the decrease in data logger size and the increase in inputs to the data loggers, the connection schemes for commercially available thermocouple connectors are not sustainable.
It is desirable to increase the number of thermocouples that can be attached to a data logger in an efficient and user-friendly manner. The present disclosure is aimed at resolving this and related problems in the art.
A first embodiment of the present disclosure describes an adapter for a data logger comprising a housing and at least two removable thermocouple connectors positioned within the housing. The housing allows easy organization of the thermocouples and allows multiple thermocouples to be simultaneously plugged into the data logger with a single male/female-type snap fit.
A second embodiment of the present disclosure describes a method of thermal profiling comprising grouping multiple thermocouples together. Each thermocouple comprises a thermocouple junction electrically connected to a first lead and a second lead. The first lead and the second lead of each thermocouple are connected to a thermocouple connector. The multiple thermocouple connectors are coupled inside of a single housing, the housing is connected to a data logger, and temperature data from the multiple thermocouples is collected via the thermocouple connectors.
The foregoing and other objects, features, and advantages of the invention will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures.
Each of the thermocouple junctions 22, 24, 26, 28, 30 includes two thermocouple leads (not shown) that are wrapped inside of a protective sheath 22′, 24′, 26′, 28′, 30′ that connect the thermocouple junctions to a thermocouple adapter 32.
In this embodiment the one or more thermocouple connectors 40 are placed into the bottom portion 56 as defined by the posts 58 with the first and second connecting pins 50, 52 positioned within the first and second slots 60, 62. The top portion 54 is then placed over the bottom portion 56 and the two portions are secured by one or more screws or fasteners as described above. In this manner it is envisioned that the top portion 54 and the bottom portion 56 hold each of the thermocouple connectors 40 securely and separately within the housing 36. It will be further recognized that the first and second slots 66, 68 of the top portion 54 and the first and second slots 60, 62 of the bottom portion 56 securely hold the first and second connecting pins 50, 52 of each of the respective thermocouple connectors 40 while simultaneously protecting and exposing the first and second connecting pins of that connector within the elongated connector 41. In this way, the connectors 40 are in electrical contact with a data logger when the adapter 32 is inserted into a port in the data logger as described above but otherwise not susceptible to mechanical damage from bending or striking that could come from activities such as being dropped or handled roughly.
It will be recognized that this configuration offers several advantages over the prior art. For example, with the thermocouples properly aligned within the adapter, an operator simply needs to snap the entire adapter into the data logger. The adapter is sensitive to orientation and can only plug in one way, making it error proof. Additionally, because multiple thermocouples are plugged in simultaneously, the speed at which the operator can plug and unplug thermocouples from the data logger is greatly increased, and with no concern of errors by plugging a thermocouple into the wrong location on the data logger. Additionally, the adapter can be configured to uniquely identify a given thermocouple quickly and easily to a user or a data logger so that it is readily known which thermocouple junction corresponds to a thermocouple connector at a first position inside of the adapter.
An additional advantage is that each of the thermocouple connectors is separate from each of the other thermocouple connectors inside of an adapter. A thermocouple including a sheath, a thermocouple junction, thermocouple leads, and a thermocouple connector can be replaced independently of each of the other thermocouples in a given adapter in the event of damage to one or more of the elements. Additionally, if fewer thermocouples are desired or one or more are damaged then each thermocouple is independently removable and replaceable from a given adapter.
Still further, the adapter allows for easy color coding by affixing labels on the adapter that are matched to color coded sheaths to associate a thermocouple with its respective position in the adapter.
Finally, by extending the first and second thermocouple leads through the thermocouple connector to serve as the first and second connecting pins, the number of connections and elements in a thermocouple is further minimized. Thus, there are fewer parts to malfunction which can lead to a reduced cost of maintenance and repair.
In view of the many possible embodiments to which the principles of the disclosed invention may be applied, it should be recognized that the illustrated embodiments are only preferred examples of the invention and should not be taken as limiting the scope of the invention. Rather, the scope of the invention is defined by the following claims. We therefore claim as our invention all that comes within the scope of these claims.
