Recommended design rules and strategies for bga devices. For pads defined with no copper layers referred to as aperture pads, the inherited clearance and ratio settings are no longer applied and the. Recommended design rules and strategies for bga devices user. This may be especially important when using micro bgas. Smd solder mask defined pads and nsmd nonsolder mask defined pads. Confessions of a pcb designer on solder mask supplyframe. The two different types of solder mask window needed are shown in figure 5, from which it is clear that pocket windows need solder mask that is much better defined and in register than gang windows. This of course is not possible when tracks are run in the spaces between pads. Contact pads are either manufactured with solder mask defined or copper defined. Choosing the right solder mask clearance for your pcb tempo. An opening in the solder mask is automatically created by the software, the same shape as the pad. The point of this is to prevent the solder mask causing a rise in the overall height of the pads at that location which can cause the module to not sit flat or make good contact with the pads after reflow. Two of the most commonly used pcb pad configuration for surfacemount packages are the solder mask defined smd and the nonsolder mask defined nsmd. Design for assemblyhdi prevention of solder bridging.
Eagle non solder mask defined nsmd pads electrical. The critical total volume of solder bumps and the critical pitch between adjacent pads are defined as. Dec 01, 2018 from prototype to production of single double and multilayer pc boards. I dont know about eagle terminology settings, but in the software i use this is the. This opening can be larger a positive expansion value or smaller a negative expansion value than the pad itself, as defined by the solder mask expansion setting. Typically pcbs manufactured with socket footprint area covered by solder mask in noncontact area. This method provides a larger surface area for the solder ball connection and provides more clearance compared to smd between pads, allowing for wider trace widths and more flexibility in the use of vias, but nsmd is more susceptible to pad lift during soldering and desoldering.
Solder bridges due to missing alone solder mask are not a regular thing at least for the board we run. The mask also aids in achieving proper soldering results by minimizing the chances of solder bridges forming between closelyspaced solder pads. Refer to above picture show the solder mask open size is bigger than the copper pad size. Smd pads include a solder mask placed over the margin of the metallization that restricts the solder pastes flow on the top of the metallization and prevents the solder from flowing on the. When preparing your printed circuit board for manufacturing, the solder mask should be defined in its own layer in your gerber files. Non solder mask defined pad nsmd and solder mask defined pad smd. Nsmd nonsolder mask defined which is the correct pcb pad. If it goes one way, the pad becomes soldermaskdefined, but if it goes the other way it is now a nonsoldermaskdefined pad.
From prototype to production of single double and multilayer pc boards. Choice of smd vrs nsmd is determined by the customer. Xilinx recommends using non solder mask defined nsmd copper bga landing pads for optimum board design. Contrast this with the non solder mask defined nsmd pad. The advantage of the nsmd pad is that the pad is smaller than that of an smd pad. Since its establishment in 1976 zuken has been a world leading eda vendor providing pcb design software solutions that maximize the efficiency of the design and manufacturing processes for many of the largest electronics companies around the world. If it goes one way, the pad becomes solder mask defined, but if it goes the other way it is now a non solder mask defined pad.
An example of a nsmd laminate crack and a packageside crack c, the laminate area contrast is modified to visually reveal the laminate crack, and a pcbside cu pad interface crack with the smd pad design d. Contrast this with the nonsolder mask defined nsmd pad. Board design guidelines for intel programmable device. Because this is a very small package with 6 pins, using non solder mask defined nsmd, or copper defined pads is not recommended. I am designing a pcb layout in eagle and in the datasheet of my modul it is said that non solder mask defined nsmd type is recommended for the solder pads on the pcb. Pcb solder mask design basics standards, materials and. My concern with these smaller components and using nsmd pads is if on one end it was part of a copper area and a single track leaving the other, once the solder mask aperture is increased by the manufacturer then one pad is going to be a lot larger in terms of copper than the other. Non solder mask defined pads involve a gap between the pad and the solder mask. Thus the pad area is defined by the opening in the solder mask.
Less solder paste is required for nonsolder mask defined pad connections. Avoiding solder mask relief issues tempo automation medium. Nonsolder mask defined pads involve a gap between the pad and the. The edge of the pad remains exposed, and a small gap is typically left between the edge of the nsmd pad and the solder mask. If its not a nonsolder mask defined nsmd pad, the solder flows into the traces for those particular pads, causing a nonuniform pad size forming under the bga, and subsequently forming cold solder joints or voids, as shown in figure 2. The copper can be made to tighter tolerances than the solder mask. Pcb board dimensions are presented only as a guideline. Typically pcbs manufactured with socket footprint area covered by solder mask in non contact area. First, use solder mask defined pads because nonsolder mask defined pads will have much lower molten solder height. Most ems providers suggest that nsmd be used because it provides tighter control of copper artwork registration compared to the positional tolerance of the solder masking process. Around each copper metal pad there is solder mask clearance.
Your pcb design software can help you maximize your productivity while. Youll need to define clearances on other features in your board like pads and vias to ensure the solder mask can prevent solder bridges from forming. Download solidworks edrawings software to view rotatable. According to ipc 4552, typical nickel plating is 36 micron and gold plating is minimum 0. Usually, you dont need to do anything in your pcb software to enable the solder mask. Should i change the design of my stencilquik stencil if the board i am using has solder mask defined pads instead of nonsolder mask defined pads. How to solder qfn mlf chips using hot air without solder paste and stencils duration. For regular nonbga components, nonsoldermask defined pads where the mask opening is larger than the pad are generally preferred.
Oct 01, 2015 there are two kinds of bga land patterns design. For pads defined with copper layers, the solder mask and solder paste clearance calculations remain the same. This limits the thickness of the traces between pads and may affect the use of vias. Exposure time is from 20 90 seconds depending upon the exposure unit used and the. In some designs there are parts with solder masks that are required to be opened for nonsolder mask defined pads, as well as parts that do not want the soldermask opened, or maybe even want it reduced for solder mask defined pads. The nonexposed areas of the solder mask pth pads, surface mount pads etc.
Smobc solder mask over bare coppera method of fabricating a printed circuit board that results in final metallization being copper with no protective metal. Dimensions and tolerances of the solder mask clearance have to be specified to ensure that the solder pad is not overlapped by the solder mask. Routing connections for custom pads since the software is able to detect and resolve routing connections to any copper object, there are no specific limitations on how you route to a. One is copper defined pads design and also called as nsmd nonsolder mask defined pads design. Solder bridges is a common fault, but can be visually inspected, and on non bga or udfn packages, easy to rework. Below a certain pinpitch threshold, we will be forced to use solder mask defined lands.
Most pcb design software packages allow you to set the distance. Which bga pad and fanout strategy is right for your pcb. Instead, the mask is created such that a gap is created between the edge of the pad and the solder mask. See how the solder mask coats the entire board except for the pads. Fortunately, there are a few options to mitigate warping. Faq solder tools, ipc training, pcb rework and solder. Solder mask relief is an area on the surface of the pcb that does not have solder mask these locations typically surround smt pads, through hole. This situation creates neither soldermaskdefined nor nonsoldermaskdefined pads. As show in figures 2a through 2c below, the solderballjoint pad with a 20 percent less diameter of a cspbga solder ball allows pcb designers to design a dogbone style layout, nsmd nonsoldermaskdefined nsmd pads with nonsolder mask covered clearance between the copper and solder mask, and to design soldermask defined smd pads with. Choose smd solder mask defined pads in the 5 outermost pads on each corner to maximize shock and bend reliability reliability considerations especially shock and bend, corner joints are more susceptible to damage from use conditions that are emulated in standard reliability testing methodologies all four corners of package, 5 pads per corner. On the other hands, smd pads have the solder mask opening smaller than the copper pad. Hi dani, hope you have typed your units wrongly as mm insted of mil. The pads are exposed to allow you to solder parts to them. Sep 03, 2016 solder mask relief is an area on the surface of the pcb that does not have solder mask these locations typically surround smt pads, through hole pads, test points and vias as a margin of error.
Nsmd pads are placed at the same elevation as the surrounding solder mask. Solder mask defined pads are suitable for fine pitch components, often used with bgas. Solder mask expansion can be defined for pads and vias on an individual basis, in the associated properties dialog. A solder bridge is a connection between two conducting parts of a board through a small, unintended blob or whisk of solder. The noncoated areas are coated by solder resist, exposing only the component terminal areas. Electronic packaging reflow shape prediction for the solder mask defined ball grid array. Difference between smd pad and nsmd pad infineon forums. Options are available to follow the expansion defined in the applicable design rule, or to override the rule and apply a specified expansion directly to the individual pad or via in question. Solder mask defined pads are pads where the solder mask opening is smaller than the pad itself. For regular non bga components, non soldermask defined pads where the mask opening is larger than the pad are generally preferred. Jun 11, 2017 how to solder qfn mlf chips using hot air without solder paste and stencils duration. C o p p e r d e f i n e d p a d s c o p p e r n i c k e l g o.
Manufacturing with intelstratix10 field programmable gate arrays. One is copper defined pads design and also called as nsmd non solder mask defined pads design. The software automatically makes holes in the mask that correspond to pads. Using nsmd may result in inconsistent soldering pad dimension and cause the package to tilt. This will allow them to be used for either configuration of pads without any changes.
No, our standard designs for the stencilquik stencils are designed to be oversized for the intended pads. Nonsolder mask defined pads involve a gap between the pad and the solder mask. Dimensions and tolerances of the solder mask clearance have to be specified to ensure that. Also, the thickness of soldermask that creeps onto the pad can prevent components e. Non solder mask defined how is non solder mask defined. Nonsolder mask definied nsmd nsmd is to use copper to define the pad area to which the solder bump will be soldered. The soldermask openings are smaller than copper pads. Nov 27, 2017 below a certain pinpitch threshold, we will be forced to use solder mask defined lands. Im currently in the process of looking to update our symbol library and wondering if to use solder mask defined smd pads or non solder mask defined nsmd pads. Solder mask the most comprehensive introduction is here.
Figure 39 shows an example of a ball grid array bga pad design. Nonsolder mask definied nsmd nsmd is to use copper to. An opening in the solder mask that is the same shape as the pad is automatically created by the software. This opening can be larger a positive expansion value or smaller a negative expansion value than the pad itself, as defined by the mask expansion settings. Nsmd pads have the solder mask opening larger than the pads. Nonsolder mask defined bga pads nsmd nsmd pads differ from smd pads as the solder mask is defined to not make contact with the copper pad. The most effective way to work with 0201s and other small parts. Hi all im currently in the process of looking to update our symbol library and wondering if to use solder mask defined smd pads or non solder. The pad on the right is not mask defined in that the copper area is smaller than the solder mask aperture.
The solder mask covers the pcb area between adjacent pads and overlaps on top on pad edges. No, it means there will be no solder mask on the pads. This situation creates neither solder mask defined nor non solder mask defined pads. In some designs there are parts with solder masks that are required to be opened for non solder mask defined pads, as well as parts that do not want the soldermask opened, or maybe even want it reduced for solder mask defined pads. Mar 16, 2014 here a ballgrid array bga package is used, with the bga pads fanned out with a thicker trace. The solder mask openings are larger than copper pads.
Solder mask defined and nonsolder mask defined in pad. Pcb design for manufacturability guidelines altron inc. Csp solder joints will have voids whenever there is a microvia on the pad fig 5. Figure 1 solder mask defined pad figure 2 nonsolder mask defined pad figure 3 cross section of smd pad figure 4 cross section of nsmd. Non solder mask defined bga pads nsmd nsmd pads differ from smd pads as the solder mask is defined to not make contact with the copper pad. There is plenty of advice that sways towards nsmd for bgas but when it comes to 0402 and 0201 chip packages there is little advice, so im asking what would you do and why. Figure 12 illustrates the difference between nsmd and smd pads. An opening in the paste and solder mask is automatically created by the software, the same shape as the pad. The following image shows a printed button that has the solder mask opening defined by a manually placed full circle arc, placed on the top solder mask layer. I know in ub gerbers can be exported with solder mask openings expanded. It is recommended to use solder mask defined smd pad to keep soldering pad dimension consistent. The following image shows a top and cross section view of a nsmd style pad. Whatever way you decide to define your pads, use the same type on the component and the board.
Less solder paste is required for non solder mask defined pad connections. Electronic packaging reflow shape prediction for the solder. Thats because molten solder doesnt have as much wicking area to spread out over. In the nsmd pad, the solder mask opening is larger than the copper pad.
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