PCB Panelization Guidelines Every Designer Should Know
There are a number of factors that impact the cost of your PCB design, but none are more basic than how many parts fit on the manufacturing panel. This guide will introduce you to the common factors involved in PCB panelization and why it's important to consider panelization early in the design process. We'll cover individual and array layouts as well as ways to analyze the part size itself for optimization.
Collaborate on panelization early in the design process
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, the minimum panel borders for each panel size and their preferred panel size. Educate yourself with the information necessary to optimize the panel layout, so you can get the most parts per panel and 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 it's best to ask.
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 individual part layout.
Let’s assume that were working with three 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 largest panel, 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 and in most cases, you'll get more parts on the panel when you allow rotations.
To rotate or not to rotate
Some PCB laminate has a grain direction and panels are typically 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 and it will occur to a greater extent with the grain. Having some parts manufactured with the gain along the length and others with the gain along the width can introduce some variation between the parts that may affect the quality of the part. The grain direction can also impact other aspects of the part such as impedance.
This is important because without rotating the parts, 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 array layout
Arrays introduce more panelization factors to consider like the number of parts on the array, the array matrix, the spacing between the parts on the array and the array borders which is the area that surrounds the parts on the array.
It's the parts per panel that matter most, not arrays per panel
Array material is waste material, so when designing an array it’s important to achieve the highest number of parts per panel, not arrays per panel. As you'll see, more parts on the array does not always equal to more parts on the panel.
Evaluate all array matrix options
There are many possible array configurations that we can choose, but 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? There are actually 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 will fit on each of the manufacturing panel sizes available to us.
Let's consider and example with these parameters. Part size: 1 x 2, part space on the array: .062, array borders: .562, spacing on the panel: .1, panel borders: .75.
If we evaluate all 21 possible array configurations on the 16 x 18, 18 x 24 and 21 x 24 panel sizes 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 designed a 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 part.
Don't forget about the part size
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 parts per panel.
The results below were generated by KwickFit and show that if we can reduce the part size from 1 x 2 to .934 x 2, we can increase the number of parts per panel on the 18 x 24 panel from 99 parts to 108 parts per panel. This improvement could lead to significant cost savings on a production run.
This illustrates the importance of evaluating panelization at the start of the design process. Reducing the part size by .066 may not be achievable in every case, but having that information at the beginning of the design is invaluable, because we may be able to make the adjustment. If we learned this after the design 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%|
Use KwickFit, it will pay for itself, time and time again
If you're a PCB designer and you leave panelization to your PCB supplier, there's a good chance you'll pay more for your PCB than you have to. However, if you bake panelization analysis into your design process, you're certain to get the best possible PCB price because you'll go to manufacturing with a design that optimized for the manufacturing panel.
KwickFit makes panelization analysis easy and always gets the most parts per panel. Remember, more parts per panel equals a lower part price.