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. Xilinx recommends using non solder mask defined nsmd copper bga landing pads for optimum board design. Solder bridges is a common fault, but can be visually inspected, and on non bga or udfn packages, easy to rework. Typically solder mask openings are larger than the pad, but there are exceptions. Choice of smd vrs nsmd is determined by the customer. How to solder qfn mlf chips using hot air without solder paste and stencils duration. Hi dani, hope you have typed your units wrongly as mm insted of mil. Typically pcbs manufactured with socket footprint area covered by solder mask in non contact area. For regular non bga components, non soldermask defined pads where the mask opening is larger than the pad are generally preferred. Two of the most commonly used pcb pad configuration for surfacemount packages are the solder mask defined smd and the nonsolder mask defined nsmd. Choosing the right solder mask clearance for your pcb tempo. 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. Csp solder joints will have voids whenever there is a microvia on the pad fig 5.
On the other hands, smd pads have the solder mask opening smaller than the copper pad. Refer to above picture show the solder mask open size is bigger than the copper pad size. Fortunately, there are a few options to mitigate warping. The soldermask openings are smaller than copper pads. Nonsolder mask defined pads involve a gap between the pad and the. 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.
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. 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. The solder mask openings are larger than copper pads. Here a ballgrid array bga package is used, with the bga pads fanned out with a thicker trace. Board design guidelines for intel programmable device. The solder mask covers the pcb area between adjacent pads and overlaps on top on pad edges. No, our standard designs for the stencilquik stencils are designed to be oversized for the intended pads. For regular nonbga components, nonsoldermask defined pads where the mask opening is larger than the pad are generally preferred. The most effective way to work with 0201s and other small parts.
Solder mask defined pads are pads where the solder mask opening is smaller than the pad itself. Around each copper metal pad there is solder mask clearance. 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. 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.
No pointofstress concentration at edge mask and solder ball no cte mismatch at edge mask and solder. Nsmd nonsolder mask defined which is the correct pcb pad. Because this is a very small package with 6 pins, using non solder mask defined nsmd, or copper defined pads is not recommended. 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 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. This situation creates neither solder mask defined nor non solder mask defined pads. Nsmd pads are placed at the same elevation as the surrounding solder mask. This situation creates neither soldermaskdefined nor nonsoldermaskdefined pads. Solder mask the most comprehensive introduction is here.
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. Pcb design for manufacturability guidelines altron inc. Usually, you dont need to do anything in your pcb software to enable the solder mask. Difference between smd pad and nsmd pad infineon forums. Also, the thickness of soldermask that creeps onto the pad can prevent components e.
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. 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. 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 following image shows a top and cross section view of a nsmd style pad. 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. Figure 39 shows an example of a ball grid array bga pad design. Dimensions and tolerances of the solder mask clearance have to be specified to ensure that. Non solder mask defined pads involve a gap between the pad and the solder mask.
First, use solder mask defined pads because nonsolder mask defined pads will have much lower molten solder height. 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. 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. Less solder paste is required for non solder mask defined pad connections. Mar 16, 2014 here a ballgrid array bga package is used, with the bga pads fanned out with a thicker trace. This of course is not possible when tracks are run in the spaces between pads. 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.
Figure 12 illustrates the difference between nsmd and smd pads. Exposure time is from 20 90 seconds depending upon the exposure unit used and the. Contrast this with the nonsolder mask defined nsmd pad. Jun 11, 2017 how to solder qfn mlf chips using hot air without solder paste and stencils duration. Nov 27, 2017 below a certain pinpitch threshold, we will be forced to use solder mask defined lands. Avoiding solder mask relief issues tempo automation medium. 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.
For pads defined with copper layers, the solder mask and solder paste clearance calculations remain the same. Non solder mask defined how is non solder mask defined. There are two basic forms of pads implemented for bga footprints. Thus the pad area is defined by the opening in the solder mask. 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. 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. According to ipc 4552, typical nickel plating is 36 micron and gold plating is minimum 0. 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. Smobc solder mask over bare coppera method of fabricating a printed circuit board that results in final metallization being copper with no protective metal. Nonsolder mask definied nsmd nsmd is to use copper to define the pad area to which the solder bump will be soldered. 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. 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.
Solder mask defined pads are suitable for fine pitch components, often used with bgas. See how the solder mask coats the entire board except for the pads. The solder mask covers the outer part of the pad, so the solderable copper surface is determined by the size of the opening in solder mask, not by the area of the copper pad. It is recommended to use solder mask defined smd pad to keep soldering pad dimension consistent. Contrast this with the non solder mask defined nsmd pad.
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. Nsmd pads have the solder mask opening larger than the pads. Solder mask defined and nonsolder mask defined in pad. The pad on the right is not mask defined in that the copper area is smaller than the solder mask aperture. Contact pads are either manufactured with solder mask defined or copper defined. Thats because molten solder doesnt have as much wicking area to spread out over. This will allow them to be used for either configuration of pads without any changes. In the nsmd pad, the solder mask opening is larger than the copper pad. Instead, the mask is created such that a gap is created between the edge of the pad and the solder mask.
Which bga pad and fanout strategy is right for your pcb. A solder bridge is a connection between two conducting parts of a board through a small, unintended blob or whisk of solder. Pcb board dimensions are presented only as a guideline. 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. This may be especially important when using micro bgas. 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. The noncoated areas are coated by solder resist, exposing only the component terminal areas. An opening in the solder mask that is the same shape as the pad is automatically created by the software. Solder mask expansion can be defined for pads and vias on an individual basis, in the associated properties dialog. Below a certain pinpitch threshold, we will be forced to use solder mask defined lands.
Nonsolder mask defined pads involve a gap between the pad and the solder mask. Using nsmd may result in inconsistent soldering pad dimension and cause the package to tilt. You need to increase the solder mask opening value further by 5 more. Copper defined pad is also called nonsoldermask defined pad. I dont know about eagle terminology settings, but in the software i use this is the. Recommended design rules and strategies for bga devices. Faq solder tools, ipc training, pcb rework and solder. Manufacturing with intelstratix10 field programmable gate arrays. 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. Pcb solder mask design basics standards, materials and.
Nonsolder mask definied nsmd nsmd is to use copper to. Download solidworks edrawings software to view rotatable. 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. Whatever way you decide to define your pads, use the same type on the component and the board. Confessions of a pcb designer on solder mask supplyframe. Eagle non solder mask defined nsmd pads electrical. One is copper defined pads design and also called as nsmd nonsolder mask defined pads design. Most pcb design software packages allow you to set the distance. Your pcb design software can help you maximize your productivity while. The copper can be made to tighter tolerances than the solder mask. Design for assemblyhdi prevention of solder bridging. 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. Nsmd pads are pads that are not covered by any solder mask, as opposed to solder mask defined smd pads in which a small amount of solder mask covers the pad landing.
No, it means there will be no solder mask on the pads. For pads defined with no copper layers referred to as aperture pads, the inherited clearance and ratio settings are no longer applied and the. One is copper defined pads design and also called as nsmd non solder mask defined pads design. The pads are exposed to allow you to solder parts to them. 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. Solder bridges due to missing alone solder mask are not a regular thing at least for the board we run. The critical total volume of solder bumps and the critical pitch between adjacent pads are defined as. The software automatically makes holes in the mask that correspond to pads. Study on solder joint reliability of fine pitch csp. The mask also aids in achieving proper soldering results by minimizing the chances of solder bridges forming between closelyspaced solder pads. This limits the thickness of the traces between pads and may affect the use of vias. Electronic packaging reflow shape prediction for the solder mask defined ball grid array. An opening in the paste and solder mask is automatically created by the software, the same shape as the pad. The advantage of the nsmd pad is that the pad is smaller than that of an smd pad.
An opening in the solder mask is automatically created by the software, the same shape as the pad. 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. Electronic packaging reflow shape prediction for the solder. 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. 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. I know in ub gerbers can be exported with solder mask openings expanded. 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. If it goes one way, the pad becomes soldermaskdefined, but if it goes the other way it is now a nonsoldermaskdefined pad. Oct 01, 2015 there are two kinds of bga land patterns design. When preparing your printed circuit board for manufacturing, the solder mask should be defined in its own layer in your gerber files. The nonexposed areas of the solder mask pth pads, surface mount pads etc.