Coplanarity challenges?
Published on 6-Jan-2009
Veldhoven, April 25th
Our policy is “Never say No” to coplanarity questions. If your question is “Can you check these specific, critical SMD parts for coplanarity and ensure they are placed properly?” our answer is ”yes”. A 3D coplanarity checker ensures exactly that on our X-Series and M-Series equipment.
Ideally, all the leads of a fine pitch component should lie in the same plane. Even a single lead that is significantly higher or lower can cause open solder joints and a defective PCB. Most specifications call for coplanarity to be within 0.004 to 0.008 inch (100 to 200 µm) of the seating plane. In practice, the distance between the highest and lowest lead cannot exceed this limit.
The most common cause of co-planarity problems comes from device handling. Leads can become bent, and solder balls can become damaged during the programming process, for example. Device manufacturing can also cause coplanarity problems through poorly formed solder balls on a BGA package. Some industries, most notably automotive, demand 100% inspection of devices for coplanarity prior to Pick & Place. Today, 3D coplanarity checkers mean that co-planarity is an easy and virtually instantaneous measurement, measuring lead deviations down to 25 µm.
Optional 3D Coplanarity Checker camera
All members of the X-Series (for example Opal-XII, Emerald-XII, Topaz-XII) and M-Series (for example MG-1R and MG-8R have a standard camera measuring the X,Y and φ for a component. These systems can also have an additional 3D Coplanarity Checker camera. This uses a line array camera to measure the lead co-planarity of a component like a QFP at high speed and high accuracy. That ensures that bad parts (as in figure 1, which shows a damaged fine pitch part with bent lead ends) are NOT placed.
QFP 100
Dimension: 16 mm x 16mm
Lead pitch: 0.05
mm
Height distribution across part
Lead width: 0.25 mm
Figure 1: damaged fine-pitch component with bent lead ends
How it works
Our X-Series and M-Series systems measure the fine pitch parts first with the standard line array camera and then with the 3D Coplanarity Checker camera (figure 2). That gives fast and reliable on-the-fly recognition.
Figure 2: Top view of a placement system with the 3D Coplanarity Checker camera installed.
Measurements detect ‘linearity’ and ‘coplanarity’, and the results (OK or NOK) are based on the coplanarity threshold parameter (deviation in μm) set in the Parts Information.
The linearity measurement measures the Z-coordinates (height) of all leads along one side of a component and hence calculates the reference line. It then calculates the height of each lead relative to the reference line and derives the adjacent lead height differences and the lead coplanarity (difference in height between the maximum and minimum lead heights on one side). These are compared with the coplanarity threshold level set in the Parts Information to determine the result.
The coplanarity measurement measures the Z-coordinates (height) of the leads along all sides and calculates the reference plane by the least square method. It then calculates the height of each lead relative to the reference plane, and obtains the adjacent lead height difference and the lead coplanarity (height difference between maximum and minimum lead heights on all sides). These are compared with the coplanarity threshold level set in the Parts Information.
Specifications of 3D Coplanarity Checker camera:
