Patent Application
20200367367
This disclosure relates to electronics and electronics assembly processing.
Stacking of printed circuit board assemblies (PCBAs) on a mother or main board suffers from multiple issues. The PCBAs (which are also known as the daughter boards) may be assembled offline. This incurs longer cycle-times. The offline assembled PCBAs are then later treated as a surface mount technology (SMT) component during the main board assembly process. That is, the PCBAs are subjected to multiple thermal excursions (depending on the stack count) for each reflow process of the main board assembly process. Designers must therefore select components that can stand multiple heat excursions due to multiple reflow processes. In addition, the multiple reflow processes may weaken joint bonds including mechanical and electrical connectivity. Alternatively, single reflow process can be abducted by depositing the solder paste on the daughter board via a jetting process. This process not only requires a massive capital investment on a jetting machine, but the constraint on the deposition size is limited to a 0.5 mm dot size (standard option) and a 0.3 mm dot size (special option), making this method unsuitable for packages smaller then a 0201 package size (which is a pad size of 0.3 mm×0.38 mm).
Disclosed herein are implementations of methods and devices for stacking printed circuit board assemblies with a single reflow process. This decreases impact on surface mount technology (SMT) component and solder joint reliability. In addition, the processes are suitable for packages smaller than the 0201-package size. A method includes transferring solder paste on to a bottom PCB and forming a bottom PCBA by placing surface mount technology (SMT) components on the bottom PCB. A middle PCB is stacked on the bottom PCBA and solder paste is transferred on to the middle PCB. A top PCB is stacked on the middle PCB and solder paste is transferred on to the top PCB. SMT components are placed on the top PCB to form a stacked assembly. The stacked assembly is reflowed in a single reflow so that all the solder paste simultaneously or nearly simultaneously melts to bond SMT components to respective PCB boards and to bond respective PCBs to each other.
The disclosure is best understood from the following detailed description when read in conjunction with the accompanying drawings and are incorporated into and thus constitute a part of this specification. It is emphasized that, according to common practice, the various features of the drawings are not to-scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity.
The figures and descriptions provided herein may be simplified to illustrate aspects of the described embodiments that are relevant for a clear understanding of the herein disclosed processes, machines, manufactures, and/or compositions of matter, while eliminating for the purpose of clarity other aspects that may be found in typical similar devices, systems, compositions and methods. Those of ordinary skill may thus recognize that other elements and/or steps may be desirable or necessary to implement the devices, systems, compositions and methods described herein. However, because such elements and steps are well known in the art, and because they do not facilitate a better understanding of the disclosed embodiments, a discussion of such elements and steps may not be provided herein. However, the present disclosure is deemed to inherently include all such elements, variations, and modifications to the described aspects that would be known to those of ordinary skill in the pertinent art in light of the discussion herein.
Embodiments are provided throughout so that this disclosure is sufficiently thorough and fully conveys the scope of the disclosed embodiments to those who are skilled in the art. Numerous specific details are set forth, such as examples of specific aspects, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. Nevertheless, it will be apparent to those skilled in the art that certain specific disclosed details need not be employed, and that embodiments may be embodied in different forms. As such, the exemplary embodiments set forth should not be construed to limit the scope of the disclosure.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. For example, as used herein, the singular forms “a”, “an” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof.
The steps, processes, and operations described herein are thus not to be construed as necessarily requiring their respective performance in the particular order discussed or illustrated, unless specifically identified as a preferred or required order of performance. It is also to be understood that additional or alternative steps may be employed, in place of or in conjunction with the disclosed aspects.
Yet further, although the terms first, second, third, etc. may be used herein to describe various elements, steps or aspects, these elements, steps or aspects should not be limited by these terms. These terms may be only used to distinguish one element or aspect from another. Thus, terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, step, component, region, layer or section discussed below could be termed a second element, step, component, region, layer or section without departing from the teachings of the disclosure.
The non-limiting embodiments described herein are with respect to a method for printed circuit board (PCB) assembly (PCBA) stacking with a single reflow. The method for PCBA stacking with a single reflow may be modified for a variety of applications and uses while remaining within the spirit and scope of the claims. The embodiments and variations described herein, and/or shown in the drawings, are presented by way of example only and are not limiting as to the scope and spirit. The descriptions herein may be applicable to all embodiments of the method for PCBA stacking in a single reflow.
Described herein is a method for PCBA stacking with a single reflow. In an implementation, the method for PCBA stacking with a single reflow includes depositing solder paste on a bottom PCB and placing surface mount technology (SMT) components on the bottom PCB. A middle PCB is placed on the bottom PCB and solder is deposited on the middle PCB. A top PCB is placed on the middle PCB and solder paste is deposited on the top PCB. SMT components are placed on the top PCB. The stacked bottom PCB with SMT components, middle PCB and top PCB with SMT components are simultaneously subjected to a reflow process. In an implementation, optical inspections may be performed after certain processes. In an implementation, solder deposition may be done using pin transfers. In an implementation, solder deposition may be done using gang pin transfers. In an implementation, pin size may define the deposited volume and size, where package sizes may range from 15 mm square to 008004 package sizes. The single assembly setup described herein improves overall product assembly cycle-time. The techniques described herein advantageously use available SMT equipment. In an implementation, a pick and place device or machine may be used for solder paste deposition using pin transfers or gang pin transfers addition to the picking and placing of PCBs on each other and the picking and placing of the SMT components on certain PCBs. For example, the certain PCBs are the top and bottom PCBs.
After solder paste inspection of the bottom PCB, the process 300 may include picking and placing 315 surface mount technology (SMT) components on the bottom PCB to form a bottom PCBA. In an implementation, the SMT components are placed on the top of the bottom PCB. The process 300 may then include picking, seeing and placing 320 a middle PCB on the bottom PCB, where the middle PCB may be the middle PCB 120 or middle PCB panel 220. The process 300 may then include inspecting 325 the placement of the SMT components on the solder paste on the bottom PCB and placement of the middle PCB on the bottom PCB. In an implementation, automated optical inspection (AOI) may be used for inspecting the SMT components to check for catastrophic failure (e.g. a missing component), quality defects and other parameters or characteristics.
The process 300 may then include depositing 330 solder paste on pads of the middle bottom PCB. In an implementation, the deposition of the solder paste may be done using a pin transfer technique on the middle PCB. The deposition techniques are illustrative and other deposition techniques may be used. In an implementation, vias are not used for the pads on the middle bottom PCB.
The process 300 may then include picking, seeing and placing 335 a top PCB on the middle PCB, where the top PCB may be the top PCB 140 or top PCB panel 240. The process 300 may then include depositing 340 solder paste on pads of the top PCB. In an implementation, the deposition of the solder paste may be done using a pin transfer technique on the top PCB. The deposition techniques are illustrative and other deposition techniques may be used. After solder paste deposition on the top PCB, the process 300 may include picking, seeing and placing 345 SMT components on the top PCB to form a top PCBA and a stacked assembly such as stacked assembly 160.
The process 300 may include pre-reflow inspecting 350 the stacked assembly for SMT component and PCB placement. In an implementation, AOI may be used for inspecting the SMT components to check for catastrophic failure (e.g. a missing component), quality defects and other parameters or characteristics, and proper placement of each PCB. The process may include reflowing 355 the stacked assembly to melt the solder to create joints between pads, component leads and the multiple PCBs. The stacked assembly is therefore subjected to one reflow process, where the solder simultaneously melts or nearly simultaneously melts in one reflow process. In an implementation where PCB panels are used, the process 300 may include depaneling 360 the stacked assembled PCB panels to form stacked assembled PCBs.
The process 500 may include the screen printer 570 depositing 505 solder paste on the bottom PCB such as bottom PCB 100 or bottom PCB panel 200, for example. In an implementation, the solder paste may be printed on the bottom PCB. In an implementation, the solder paste may be printed on the bottom PCB using a stencil. The deposition techniques are illustrative and other deposition techniques may be used. The process 500 may include the inspection device 574 inspecting 510 the solder paste deposited on the bottom PCB for proper solder paste deposition.
After solder paste inspection of the bottom PCB, the process 500 may include the pick and place device 578 picking and placing 515 SMT components on the bottom PCB to form a bottom PCBA. In an implementation, the pick and place device 578 may place the SMT components on the top of the bottom PCB. The process 500 may then include the pick and place device 578 picking, seeing and placing 520 a middle PCB on the bottom PCB, where the middle PCB may be the middle PCB 120 or middle PCB panel 220. The process 300 may then include the AOI device 582 inspecting 525 the placement of the SMT components on the solder paste on the bottom PCB and placement of the middle PCB on the bottom PCB. In an implementation, the AOI device 582 may be used for inspecting the SMT components to check for catastrophic failure (e.g. a missing component), quality defects and other parameters or characteristics.
The process 500 may then include the pick and place device 578 depositing 530 solder paste on pads of the middle bottom PCB. In an implementation, the pick and place device 578 may be perform deposition by using pin transfer techniques on the middle PCB. The deposition techniques are illustrative and other deposition techniques may be used. In an implementation, vias are not used for the pads on the middle bottom PCB.
The process 500 may then include the pick and place device 578 picking, seeing and placing 535 a top PCB on the middle PCB, where the top PCB may be the top PCB 140 or top PCB panel 240. The process 500 may then include the pick and place device 578 depositing 540 solder paste on pads of the top PCB. In an implementation, the pick and place device 578 may perform deposition of the solder paste using a pin transfer technique on the top PCB. The deposition techniques are illustrative and other deposition techniques may be used. After solder paste deposition on the top PCB, the process 500 may include the pick and place device 578 picking, seeing and placing 545 SMT components on the top PCB to form a top PCBA and a stacked assembly such as stacked assembly 160.
The process 500 may include the inspection device 586 pre-reflow inspecting 550 the stacked assembly for SMT component and PCB placement. In an implementation, AOI may be used for inspecting the SMT components to check for catastrophic failure (e.g. a missing component), quality defects and other parameters or characteristics, and proper placement of each PCB. The process may include using the reflow oven 590 for reflowing 355 the stacked assembly to melt the solder to create joints between pads, component leads and the multiple PCBs. A temperature profile for the reflow oven is shown in
After solder paste inspection of the bottom PCB, the process 800 may include picking and placing 815 surface mount technology (SMT) components on the bottom PCB to form a bottom PCBA. In an implementation, the SMT components are placed on the top of the bottom PCB. The process 800 may then include picking, seeing and placing 820 a middle PCB on the bottom PCB, where the middle PCB may be the middle PCB 120, middle PCB panel 220 or middle PCB panel 710. The process 800 may then include inspecting 825 the placement of the SMT components on the solder paste on the bottom PCB and placement of the middle PCB on the bottom PCB. In an implementation, automated optical inspection (AOI) may be used for inspecting the SMT components to check for catastrophic failure (e.g. a missing component), quality defects and other parameters or characteristics.
The process 800 may then include gang pin transferring 830 solder paste on pads of the middle bottom PCB. The deposition techniques are illustrative and other deposition techniques may be used. In an implementation, vias are not used for the pads on the middle bottom PCB.
The process 800 may then include picking, seeing and placing 840 a top PCB on the middle PCB, where the top PCB may be the top PCB 140, top PCB panel 240 or top PCB panel 720. The process 800 may then include gang pin transferring 845 solder paste on pads of the top PCB. The deposition techniques are illustrative and other deposition techniques may be used. The process 800 may then include inspecting 850 the solder paste deposited on the top PCB for proper solder paste deposition. After inspection of the solder paste deposition on the top PCB, the process 800 may include picking, seeing and placing 855 SMT components on the top PCB to form a top PCBA and a stacked assembly such as stacked assembly 160.
The process 800 may include pre-reflow inspecting 860 the stacked assembly for SMT component and PCB placement. In an implementation, AOI may be used for inspecting the SMT components to check for catastrophic failure (e.g. a missing component), quality defects and other parameters or characteristics, and proper placement of each PCB. The process may include reflowing 865 the stacked assembly to melt the solder to create joints between pads, component leads and the multiple PCBs. The stacked assembly is therefore subjected to one reflow process, where the solder simultaneously melts or nearly simultaneously melts in one reflow process. The process 800 may include inspecting 870 the reflowed stacked assembly for SMT component and PCB bonding. In an implementation, AOI may be used for inspecting the SMT components and each PCB for joint bonding. In an implementation where PCB panels are used, the process 300 may include depaneling 875 the stacked assembled PCB panels to form stacked assembled PCBs.
The method 900 includes depositing 905 solder paste on a bottom PCB or bottom PCB panel. In an implementation, solder paste deposition is done by screen printing. In an implementation, solder paste deposition is done by pin transfer. In an implementation, solder paste deposition is done by gang pin transfer. In an implementation, a pick and place device may be used for pin transfer and/or gang pin transfer. In an implementation, the solder paste is deposited on pads. In an implementation, the depositing 905 may include inspecting the bottom PCB or bottom PCB panel after solder paste deposition. In an implementation, an AOI may be used to do the inspecting.
The method 900 includes picking and placing 910 SMT components on the bottom PCB or bottom PCB panel. A bottom PCBA or bottom PCBA panel is formed after placement of the SMT components. In an implementation, a pick and place device may be used for SMT component pick and placement. In an implementation, the picking and placing 910 may include inspecting the SMT component pick and placement. In an implementation, an AOI may be used to do the inspecting.
The method 900 includes picking and placing 915 a middle PCB or middle PCB panel on the bottom PCBA or bottom PCBA panel. In an implementation, the middle PCB or middle PCB panel may be multiple middle PCBs or middle PCB panels. In an implementation, a pick and place device may be used for middle PCB or middle PCB panel pick and placement. In an implementation, the picking and placing 915 may include inspecting the SMT component pick and placement. In an implementation, the picking and placing 915 may include inspecting middle PCB or middle PCB panel pick and placement on the bottom PCBA or bottom PCBA panel. In an implementation, the picking and placing 915 may include inspecting the SMT component pick and placement and inspecting middle PCB or middle PCB panel pick and placement on the bottom PCBA or bottom PCBA panel. In an implementation, an AOI may be used to do the inspecting.
The method 900 includes depositing 920 solder paste on the middle bottom PCB or middle PCB panel. In an implementation, solder paste deposition is done by screen printing. In an implementation, solder paste deposition is done by pin transfer. In an implementation, solder paste deposition is done by gang pin transfer. In an implementation, a pick and place device may be used for pin transfer and/or gang pin transfer. In an implementation, the solder paste is deposited on pads. In an implementation, the depositing 920 may include inspecting the middle PCB or middle PCB panel after solder paste deposition. In an implementation, an AOI may be used to do the inspecting.
The method 900 includes picking and placing 925 a top PCB or top PCB panel on the middle PCB or middle PCB panel. In an implementation, a pick and place device may be used for top PCB or top PCB panel pick and placement. In an implementation, the picking and placing 925 may include inspecting top PCB or top PCB panel pick and placement on the middle PCB or middle PCB panel. In an implementation, an AOI may be used to do the inspecting.
The method 900 includes depositing 930 solder paste on the top PCB or top PCB panel. In an implementation, solder paste deposition is done by screen printing. In an implementation, solder paste deposition is done by pin transfer. In an implementation, solder paste deposition is done by gang pin transfer. In an implementation, a pick and place device may be used for pin transfer and/or gang pin transfer. In an implementation, the solder paste is deposited on pads. In an implementation, the depositing 930 may include inspecting the top PCB or top PCB panel after solder paste deposition. In an implementation, an AOI may be used to do the inspecting.
The method 900 includes picking and placing 935 SMT components on the top PCB or top PCB panel to form a stacked assembly. A top PCBA or top PCBA panel is formed after placement of the SMT components. In an implementation, a pick and place device may be used for SMT component pick and placement. In an implementation, the picking and placing 935 may include inspecting the SMT component pick and placement. In an implementation, the picking and placing 915 may include inspecting top PCBA or top PCBA panel pick and placement on the middle PCB or middle PCB panel. In an implementation, the picking and placing 935 may include inspecting the SMT component pick and placement and inspecting top PCBA or top PCBA panel pick and placement on the middle PCB or middle PCB panel. In an implementation, an AOI may be used to do the inspecting.
The method 900 includes reflowing 940 the stacked assembly in a single reflow. The reflowing 940 simultaneously or nearly simultaneously melts the solder paste to form bonds or joint bonds between the SMT components and each of the PCB boards and between each of the respective PCB boards in one reflow process or operation. In an implementation, the reflowing 940 may include inspecting of the stacked assembly after reflow. In an implementation, an AOI may be used to do the inspecting. In an implementation, the reflowing 940 may include pre-reflow inspecting of the stacked assembly. In an implementation, an AOI may be used to do the inspecting. In an implementation, when PCB panels may be used, the reflowing 940 includes depaneling the reflowed stacked assembly to obtain PCBs.
The construction and arrangement of the methods as shown in the various exemplary embodiments are illustrative only. Although only a few embodiments have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials and components, colors, orientations, etc.). For example, the position of elements may be reversed or otherwise varied and the nature or number of discrete elements or positions may be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present disclosure. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes, and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments without departing from the scope of the present disclosure.
Although the figures may show a specific order of method steps, the order of the steps may differ from what is depicted. Also two or more steps may be performed concurrently or with partial concurrence. Such variation will depend on the software and hardware systems chosen and on designer choice. All such variations are within the scope of the disclosure. Likewise, software implementations could be accomplished with standard programming techniques with rule-based logic and other logic to accomplish the various connection steps, processing steps, comparison steps, and decision steps.
While the disclosure has been described in connection with certain embodiments, it is to be understood that the disclosure is not to be limited to the disclosed embodiments but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.
