Panelization Guidelines Every PCB Designer Needs to Know
PCB panelization is an important design concern
There are a number of factors that impact the manufacturability of your design, but none are more basic than how many parts will fit on the manufacturing panel. This guide will introduce you to common factors involved in PCB panelization and why it's importance to consider panelization early in the design process to get the lowest price from your PCB supplier.
We discuss individual and array layouts and an often overlooked but extremely important factor, the part size itself. Every PCB designer should familiarize themselves with the intricacies of panelization and bake them into the design process at the start.
Start thinking about panelization early in the design process
Increasing part per panel yield is often the easiest way to lower PCB manufacturing costs.
Start by developing a relationship with a PCB supplier. Learn about their process capability, the panel sizes they use, the part space on the panel and the minimum panel borders for each panel size. You’ll also want to know their preferred panel size. Ask how your part will be run in both prototype and production. Your goal is to educate yourself with the information necessary to optimize the panel layout and get the best PCB part price. Since most manufacturers use similar tooling, these parameters will be fairly consistent across manufacturers. However, each supplier may have a different process capability, so check with each of them. Finally, design your part for the production run, not the prototype. During the prototype run, the supplier may purposely run a less optimized panel to speed manufacturing for a fast turn around.
The individual part layout
The individual part layout is the simplest panel layout. Even if you’re designing an array, it's important to understand the basics of the single part layout.
Let’s assume that your PCB supplier has three standard panel sizes. 16 x 18, 18 x 24 and 21 x 24. For each panel we'll use a .1 part spacing and minimum panel boarders of .75.
Let's also assume that your part size is 5.1 x 8. When we calculate the optimum layout for each panel size it's not surprising that the 21 x 24 panel gets the most parts per panel. The 21 x 24 offers 9 parts per panel, where the 16 x 18 and 18 x 24 both offer fewer parts per panel.
You’ll notice that some of the parts on the 16 x 18 and 21 x 24 panels are rotated to achieve the best layout. If we look at the other possible layouts for the 16 x 18 and 21 x 24 panels we see that rotating the parts got one more part per panel than the best non-rotated option on either panel. So allowing part rotations provided the best results on two of the three panel sizes.
To rotate or not to rotate
You’ll have to decide if you want to allow part rotations on the panel. In most cases, you'll get more parts on the panel when you allow rotations.
Some PCB laminate has a grain direction. In most cases, panels are sheared so the grain is in the short dimension of the panel. If you allow rotations on the panel, you’ll have some parts where the grain runs along the length of your part and some where the grain runs along the width. During manufacturing, the laminate can stretch and shrink typically to a greater extent in the grain direction of the panel, which could introduce some variation between the parts. The grain direction can impact other aspects of the part such as the impedance of your design.
With rotations disabled, the story changes. The 21 x 24 panel is no longer the best choice. The 21 x 24 produces the same number of parts per panel as the 18 x 24 panel and the 18 x 24 panel has a higher part to panel utilization which means less waste and a lower part price. So without rotations, the 18 x 24 panel is the best choice. The key takeaway is that you should not assume that the largest panel will always produce the most parts per panel.
The array layout
PCB’s are frequently manufactured in arrays to streamline the assembly process. Rather than assembling a single part, several parts are assembled in one operation.
Arrays introduce two more panelization factors to consider, the spacing between the parts on the array and the array borders which is the area that surrounds the parts on the array or the distance from the edge of the part to the edge of the array. The 3 x 1 array drawing below has a part spacing of .062 and .562 array borders.
It's the parts per panel that matter, not arrays per panel
Array material is waste material, so when designing an array it’s important to remember that you're working to achieve the highest number of parts per panel, not arrays per panel. As you'll see in what follows, more parts on the array does not always equate to more parts on the panel.
Evaluate all array matrix options
Let’s say we'd like a minimum of 4 and a maximum of 10 parts on an array. We need to determine which array design yields the most parts per panel. It is 2 x 2, 4 x 2, 2 x 5, 4 x 1, 1 x 10, etc? Maybe an 8 up array with a 4 x 2 matrix is best. There are 21 possible array matrix configurations in the range of 4 to 10 parts. To perform a thorough analysis, we'll need to consider how each of the 21 possible array designs fits on each of your suppliers standard panel sizes.
Design the array for the manufacturing panel
We'll use Part size: 1 x 2, part space on the array:.062, array borders: .562, array space on the panel: .1, panel borders: .75 for what follows.
If we evaluate all 21 possible array configurations on 16 x 18, 18 x 24 and 21 x 24 panels we'll find two optimal array designs for different panel sizes. The 16 x 18 and 21 x 24 panel both get the most parts per panel with a 5 x 2 array, but the 18 x 24 panel gets the most parts per panel with a 3 x 3 array. The 5 x 2 array yields only 90 parts on the 18 x 24 panel.
This illustrates the importance of designing the array for the manufacturing panel. If we went to production with the 5 x 2 array and our supplier needed to use the 18 x 24 panel size due to process capability limitations, we'd lose 9 parts per panel. A loss of 9 parts per panel means we'd pay a higher price for each printed circuit board which will be costly on a large production run.
Use KwickFit's Auto Matrix and Semi-Fixed Size array calculators
KwickFit makes array analysis easy. The Auto Matrix and Semi-Fixed Size array layouts can calculate all possible array combinations and find the best array design on as many different panel sizes as you like. KwickFit will pay for itself may times over with time savings and optimized array designs that yield the lowest PCB part price.
Always evaluate the part size, right from the start
This is extremely important. Know how the part size affects the panelization. More specifically, know the threshold at which a reduced part size will increase the part per panel yield.
The table below was generated from KwickFit's "Analyze Part Size to Increase Yield" feature and was run on the same array design we've been working with. The results show a reduced part size that increases the part per panel for each of our panel sizes.
We can see that if we can reduce the part size from 1 x 2 to .934 x 2, we can increase the part per panel yield on the 18 x 24 panel from 99 parts per panel to 108 parts per panel. This improvement could lead to huge savings on a production run.
Finally, this highlights the importance of evaluating panelization at the beginning of the design process. Reducing the part size by .066 may not be achievable in every case, but if it is possible and we discovered it after the design process was finished, it would likely be too late to consider it.
|Panel||Original Qty||Better Qty||Part Size||Change X||Change Y||
|16 x 18||60||63||1 x 1.984||0||-0.016||4.76%|
|18 x 24||99||100||1 x 1.889||0||-0.111||1%|
|18 x 24||99||108||0.934 x 2||-0.066||0||8.33%|
|16 x 18||60||63||0.929 x 2||-0.071||0||4.76%|
|18 x 24||99||100||0.95 x 1.951||-0.05||-0.049||1%|
|21 x 24||120||126||0.912 x 2||-0.088||0||4.76%|
|21 x 24||120||130||1 x 1.807||0||-0.193||7.69%|
|21 x 24||120||126||0.934 x 1.934||-0.066||-0.066||4.76%|