{"id":825,"date":"2023-06-23T10:25:51","date_gmt":"2023-06-23T02:25:51","guid":{"rendered":"https:\/\/www.jingpengpcb.com\/?p=825"},"modified":"2026-10-02T17:27:40","modified_gmt":"2026-10-02T09:27:40","slug":"hdi-pcb-considerations-manufacturability-cost","status":"publish","type":"post","link":"https:\/\/www.jingpengpcb.com\/en\/blog\/hdi-pcb-considerations-manufacturability-cost\/","title":{"rendered":"9 Factors to Consider When Evaluating the Feasibility and Cost of HDI Manufacturing"},"content":{"rendered":"<p>At a certain level of circuit complexity, the use of high-density interconnects (HDI) with blind vias and buried vias (<a href=\"https:\/\/www.jingpengpcb.com\/en\/hdi-pcb\/\" target=\"_blank\" rel=\"noopener\">HDI<\/a>) This architecture is more effective than through-hole designs for increasing yield and reducing costs. In this presentation, we will discuss several design examples and explain the relative costs and advantages of different architectural approaches.<\/p>\n<p>Today, we will discuss the manufacturability and cost considerations of HDI PCBs. Specifically, we will focus on design<a href=\"https:\/\/www.jingpengpcb.com\/en\/hdi-pcb\/\" target=\"_blank\" rel=\"noopener\">High-Density Interconnect (HDI) Boards<\/a>Key points to keep in mind.<\/p>\n<h2>Control Costs<\/h2>\n<p>One challenge designers face is how to control costs. My goal is to offer some insights to help you with the decision-making process. So, let\u2019s get started! When making PCB design decisions for HDI, one of the key considerations is manufacturability and cost. Just as with standard PCB design,<a href=\"https:\/\/www.jingpengpcb.com\/en\/hdi-pcb\/\" target=\"_blank\" rel=\"noopener\">HDI Board<\/a>There are four main areas of focus: HDI PCB materials, stacking and lamination, through-holes in HDI categories, and optimal trace routing and spacing.<\/p>\n<p>Let\u2019s start with materials. Materials play a crucial role in both the manufacturability and direct cost of a circuit board. Here\u2019s a tip: The goal is always to select materials that are suitable for manufacturability while meeting both thermal and electrical requirements. When selecting materials, make sure your high-speed materials are also suitable for HDI designs. There are many other factors to consider when choosing materials that are appropriate for your design.<\/p>\n<p>When considering hierarchy and layering, keep the following questions in mind:<\/p>\n<ul>\n<li>Have you made plans to reduce the number of EMI levels?<\/li>\n<li>Have you determined the routing density?<\/li>\n<li>What is the total number of sequential laminations?<\/li>\n<li>Have you minimized the number of layers?<\/li>\n<\/ul>\n<h2>Through-Hole Structure<\/h2>\n<p>Next, let\u2019s talk about through-holes. Manufacturing feasibility primarily involves the structure of through-holes. Before starting your next project, ask yourself the following questions: Do you meet the design guidelines for the aspect ratio of micro-through-holes? Are you stacking or staggering the micro-through-holes?<\/p>\n<p>Finally, let\u2019s discuss trace widths and spacing. Have you considered reducing trace widths to increase density and ultimately reduce the number of layers? Here\u2019s a brief introduction to Jingpeng Circuits: If you\u2019re considering reducing trace widths to increase density and reduce the number of layers, 2-mil traces and spacing may be exactly what you\u2019re looking for. Our yield rate for this density reaches 90%. When considering the manufacturability and cost of HDI boards, it is very important to remember that none of these factors can be addressed in isolation. For example, reducing trace widths and spacing will always result in fewer layers. Or, how do you plan the sizes of vias and pads, which in turn affect the space available for routing traces?<\/p>\n<h2>Complexity equals higher costs<\/h2>\n<p>A quick note on the manufacturability and cost considerations for layers and laminates: As a general rule, costs increase as the complexity of the stack increases.<\/p>\n<p>On the left side of this chart, you can see the HDI stacking categories, and on the right are the corresponding costs. The more sequential laminations there are, the higher the cost. The most expensive stacking category is three sequential laminations. This involves stacking micro-vias on top of each other, which is necessary when dealing with very tight BGA pitch (such as 0.3 mm). The second-most expensive option is the non-conductive via process. We\u2019ll cover this in more detail later.<\/p>\n<h2>Mechanical Drilling or Laser Drilling<\/h2>\n<p>It is important to understand the advantages and disadvantages of mechanical drilling and laser drilling. Let\u2019s start with mechanical drilling. Drilling is a major cost driver. This chart shows why:<\/p>\n<p>To give a few examples: the cost of the drill bit, the time required for mechanical drilling, and the quality of the drill bit. On the right is the cost index. If you compare the prices of a 6-mil drill bit and a 10-mil drill bit, the former is much more expensive. Is the use of hybrid laminates a factor that adds complexity to this process? Different materials require different drilling cycles and plasma cycles. In short, if you have the opportunity to reduce or eliminate mechanically drilled holes and switch to laser-drilled microvias, you can achieve significant direct cost savings in terms of yield.<\/p>\n<p>Strangely enough, designers often seem to want to add more holes to protect critical traces. However, to reduce costs and cycle time, you can use laser-drilled holes instead of through-holes in your design. Laser-drilled holes are not expensive. The cost of one laser drilling machine is the same as the cost of 10,000 laser drilling machines.<\/p>\n<h2>Filling Conductive Holes or Non-Conductive Holes<\/h2>\n<p>Returning to cost considerations, the next factor to consider is whether to choose a conductive via fill or a non-conductive via fill process. Do you have through-holes located beneath surface-mount components that need to be filled and covered or plated? This is a costly process because it requires two plating steps and two drilling steps. We drill separate holes on the circuit board, which will be filled individually rather than as standard through-holes, and any additional steps mean additional costs. In this case, we need to perform the drilling and plating twice, which consumes both time and money.<\/p>\n<p>The ultimate goal of via filling is to facilitate the assembly of high-quality solder joints. In this regard, it works very well. Just be mindful of the additional costs and time involved. If you have the option between offset laser-drilled microvias and pad-internal via designs, I would choose laser-drilled microvias over mechanically drilled ones.<\/p>\n<p>Jingpeng can perform electroplating on both laser-drilled and mechanically drilled holes. Furthermore, compared to through-hole designs within pads, mechanical drilling not only requires additional process steps but also poses challenges for the manufacturing alignment system. If you use mechanical drilling instead of laser drilling to implement a pad-through-hole design, you will need to add an additional step for the non-conductive filling process. The cost of using non-conductive filling is higher than that of plating to seal laser-drilled holes.<\/p>\n<h2>Laser-Drilled Micro-Vias<\/h2>\n<p>The following outlines the basic structure of laser-drilled microvias. Key dimensions include pad size, laser-drilled hole size, and the extruded thickness of the material. You must define the laser-drilled hole size based on the final extruded thickness to ensure proper in-hole plating. Laser-drilled holes can be very small. However, keep in mind that they only extend from one layer to another. Many manufacturers can laser-drill a 2-mil hole, but plating a 2-mil hole becomes challenging due to aspect ratio issues caused by the hole\u2019s diameter.<\/p>\n<p>Some manufacturers claim they can achieve a 1:1 aspect ratio, but this is not ideal. To ensure good plating results, you should maintain an aspect ratio of 0.75:1. The shape of microvias is critical for ensuring proper flow of the plating solution and for successfully plating or filling the microvias. If you need stacked vias\u2014that is, buried vias\u2014you\u2019ll need to choose between offset vias and stacked vias.<\/p>\n<p>Let me explain the difference between offset holes and stacked holes.<br \/>\nOffset holes essentially mean fewer process steps. We do not need to fill the laser-drilled holes with copper, because the second laser drilling will not align with the first. Typically, the plating to close laser-drilled microvias is performed in a specially designed electroless plating tank. The microvias are plated from the bottom to the top of the hole until they are completely filled. Plating to close laser-drilled microvias adds time and cost. This is only necessary when stacking inner layers\u2014or if your outer layer has pad-to-pad through-holes. If the second laser-drilled via is misaligned or offset, copper plating to close the via is not required. If your laser-drilled vias are misaligned, it is important to understand the spacing requirements between laser-drilled vias specified by the manufacturer.<\/p>\n<h2>Accuracy of Laser Drilling<\/h2>\n<p>How accurate is laser drilling? It is a very safe assumption to say that the accuracy is within plus or minus 1 mil. Typically, when creating offset microvias, the diameter of the access hole is the same as that of the underlying microvia. The key parameter that determines whether offsetting is possible without filling the underlying microvia is the dimension E\u2014that is, the vertical distance between the centerlines of the two microvias. For offsetting to be a viable option, the value of E must be greater than the microvia diameter.<\/p>\n<p>Sometimes, space constraints are so severe that your only option is to stack vias. There are a few considerations to keep in mind regarding stacked vias: Stacking over buried mechanically drilled vias is considered a structurally weak and failure-prone configuration. We have seen cracks develop at these junctions. However, we have not observed any cracks in stacked laser-drilled microvias. Please refer to our case studies to learn how we designed 8-layer and 14-layer HDI boards using stacked microvias to meet space constraints and design specifications.<\/p>\n<p>One final point: If you have a countersunk hole, it\u2019s best to offset the laser-drilled hole from the countersunk mechanical hole and stack them starting from that point; this will result in the most reliable connection.<\/p>\n<h2>HDI Stack Categories<\/h2>\n<p>Next, we\u2019ll review the different stack-up categories for HDI boards. The first option I\u2019d like to introduce is a single-layer stackup built using laser drilling. From the perspective of the most cost-effective way to utilize microvia holes, this stackup category is as simple as it gets: it uses only a single layer. When you use laser drilling, you can achieve smaller pad and via sizes. This can help alleviate some design constraints and reduce design time.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-828\" src=\"https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/06\/1-N-1.jpg\" alt=\"1+N+1\" width=\"681\" height=\"379\" srcset=\"https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/06\/1-N-1.jpg 681w, https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/06\/1-N-1-300x167.jpg 300w\" sizes=\"auto, (max-width: 681px) 100vw, 681px\" \/><\/p>\n<p>When discussing possible structures, it is important to understand the process steps associated with stacking. Additional process steps mean higher costs and greater yield loss. In the example below, an extra layer has been added to the stack, and the microvias have not been stacked. The buried vias are created through mechanical drilling. For this via, no conductive fill is required. It will naturally be filled with dielectric material. The second stacking layer adds the top and bottom layers. We then complete the final mechanical drilling.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-827\" src=\"https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/06\/2-N-2.jpg\" alt=\"2+N+2\" width=\"681\" height=\"385\" srcset=\"https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/06\/2-N-2.jpg 681w, https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/06\/2-N-2-300x170.jpg 300w, https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/06\/2-N-2-400x226.jpg 400w\" sizes=\"auto, (max-width: 681px) 100vw, 681px\" \/><\/p>\n<p>Now I\u2019d like to challenge you to consider whether you really need that final mechanical drilling step. You can achieve the same connection results using laser drilling and buried mechanical drilling. This saves an extra drilling cycle and alleviates the registration issues manufacturers face when handling both mechanical and laser drilling.<\/p>\n<p>The next stack-up configuration is more complex and is known as 3-N-3. At this stage, material selection becomes critical. Is your material strong enough to withstand four stack-up cycles, plus the reflow cycle during assembly, as well as any rework that may be required afterward?<\/p>\n<p>Finally, returning to the issue of trace spacing, the closer you can place the traces, the fewer stack-up layers you\u2019ll likely need. If you combine tighter trace spacing with smaller pad sizes achieved through laser drilling, you\u2019ll have more additional space for routing. This is why designers most often use laser drilling when working with components that have tight spacing.<\/p>\n<h2>0.4-millimeter-pitch components<\/h2>\n<p>Here is an example of a design rule we use for components with a 0.4-millimeter pitch. We also have a guide that lists design rules for other pitches. Using laser drilling can reduce pad size, freeing up space for traces within the BGA area.<\/p>\n<p>In this example, we have two traces on the inner layers, routed between the pads, and one trace on the outer layer. It is easier to etch tighter traces and spacing on the inner layers than on the outer layers because the inner layers do not have a copper plating layer. In addition, the semi-finished process provided by Jingpeng has helped us achieve very high yield rates, with fine lines and tight spacing down to 1 millimeter for both traces and spacing.<\/p>","protected":false},"excerpt":{"rendered":"<p>\u5728\u67d0\u79cd\u7535\u8def\u590d\u6742\u5ea6\u6c34\u5e73\u4e0a\uff0c\u91c7\u7528\u5177\u6709\u76f2\u5b54\u548c\u57cb\u5b54\u7684\u9ad8\u5bc6\u5ea6\u4e92\u8fde\uff08HDI\uff09\u67b6\u6784\u6bd4\u901a\u5b54\u8bbe\u8ba1\u66f4\u6709\u5229\u4e8e\u63d0\u9ad8\u4ea7\u91cf\u548c\u964d\u4f4e\u6210\u672c\u3002\u5728\u672c [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":6052,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"slim_seo":{"title":"9 Factors to Consider When Evaluating the Feasibility and Cost of HDI Manufacturing","description":"What are the nine key factors to consider when evaluating the manufacturability and cost of HDI? This article explains each factor in detail\u2014from through-hole structures and drilling methods to via filling, stack-up categories, and component spacing\u2014and provides guidance on selecting the appropriate architecture."},"_slim_seo_primary_term_category":0,"_slim_seo_primary_term_post_tag":0,"footnotes":""},"categories":[26],"tags":[46,47],"class_list":["post-825","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-blog","tag-hdi","tag-47"],"_links":{"self":[{"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/posts\/825","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/comments?post=825"}],"version-history":[{"count":1,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/posts\/825\/revisions"}],"predecessor-version":[{"id":19125,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/posts\/825\/revisions\/19125"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/media\/6052"}],"wp:attachment":[{"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/media?parent=825"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/categories?post=825"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/tags?post=825"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}