Picking a Pick and Place

From Cogwheel Circuit Works

Overview

A key piece of equipment in electronic assembly is the Pick and Place machine or ‘PnP’ for short. A PnP places electronic components onto circuit boards. These days, the majority of components are about the size of a grain of rice and smaller, making hand assembly meticulous or impossible. Fully automated PnP machines with a basic set of features start at $35k. High volume, large capacity PnP machines can have price tags well north of $150k. This may seem steep, but since they are treated as something called ‘capital equipment’ by the bean-counters, you get to treat them as ‘Assets’ and ‘Depreciate’ them which, trust me, the bean-counters consider a Good Thing(tm) . The take-away is that their price tags shouldn’t give you as much sticker shock as you initially might think. For instance, if you are borrowing money from your Aunt Stella and she asks “What if you go under in a year ?”, after telling her that’s not ‘gonna happen, tell her that you can liquidate your assets and the PnP machine is likely to recover most of its value. Promise her some free assembly runs too :)

Feeder Requirements

Feeders are the parts of the PnP which supply(aka feed) components to be placed on the board. Feeders are designed for the packaging that the components are supplied in. There are many types of packaging – Loose, Tape, Tube and Tray are just a few.

Selecting a Pick and Place is driven by the size and type of components you intend to place. I analyzed some typical designs and determined my designs fit the following mix:

Part Type	Footprint	Packaging	% of Total in Typical Design
Small Inductors, Resistors, Capacitors, Transistors, Diodes	0603,0805,1206,SOT23	8mm wide tape	~50%
Medium Inductors, Resistors, Capacitors, Transistors, Diodes, Small ICs	2420, SMB,8-SOIC, 2010	12mm wide tape	~25%
SMD Crystals, Medium ICs,	16-SOIC, 14-SOIC, Medium BGA, Leadless, SOIC	16mm wide tape	~12.5%
Larger ICs, Small Connectors, Small Electrolytic Capacitors,	SOW-24, USB mini-b, Cap 10mm Radial, BGA, Small PLCC	24mm wide tape	<~3%
Larger ICs, Connectors	Power Inductor	32mm wide tape	<~3%
Other ICs, Modules, Connectors	TQFP, Large PLCC, BGA	Waffle Tray or Loose	<~3%
Certain SOICs	16-SOIC, 14-SOIC, etc	Tube	<~3%

It should be noted that determining the width of the tape and the specific packaging is usually buried deep in the component data sheet and typically a big pain in the tuckus to locate. Often, the packaging is driven by the distributor. Sometimes exact packaging cannot be predicted when ordering small quantities;

Armed with this general information our requirements for feeders are:

Waffle Tray – Highly desirable as an IC tray area can also be used for cut tape, or any part that can be laid out into a consistent X,Y array. Some parts arrive in waffle trays. Custom waffle trays can be easily laser cut. Some machines are sophisticated enough to be able to pick, align, and place parts placed randomly on the flat tray area, but this could slow down training and placement quite a bit.

Tape Feeders – As many lanes as possible. Order 8mm tape feeders in the largest number, w/some capability for 12mm. Larger 16mm, 24mm, and 32mm would be desirable but not mandatory to start off with as parts that large can be placed into trays

Tube Feeders – Desirable, but not mandatory as their functionality can be substituted by laser cutting custom waffle trays as previously mentioned.

Other Requirements

The machine should be able to place larger modules such as Wi-Fi or ZigBee radios, Leadless and BGA parts, and smaller parts below 0603 such as 0201

The Contenders

During my pre-purchase research in 4Q2012, Two machines made the shortlist (update 1Q2014: no new contenders in this price class):

Manncorp FVX

This machine is based off of the earlier Manncorp 7722FV machine, which originally designed and manufactured by Japanese company MDC. This model is used by Adafruit Industries and numerous others. It is the least expensive and generally highly capable, and meets all the basic requirements

Manncorp MC-400

This machine is actually designed by Autotronik of Germany and manufactured in Asia. It is sold in North America by Manncorp as the MC-400. It has a high degree of commonality with the Manncorp MC-385 series, and uses the same feeders. They are used by such companies as DIY Drones, Polulu, Spark Fun and many, many others. While more expensive than the FVX, it uses the same smart feeders as the MC-385 series which means a very easy upgrade path to the next level.

Machine Comparison

FEATURE	Manncorp FVX	Manncorp MC-400
Tape Feeder Lanes	54	64
Waffle Tray Area	Yes	Yes
Tube Feeder	Yes	Yes
Max PCB/Panel Size	390 x 310mm (Shared with Waffle Tray Area)	415×320 (Shared with Waffle Tray Area)
Placement Speed	2200 placements per hour	3000 placements per hour
Minimum Component Size	0201	01005(ridiculously tiny, BTW)
Placement accuracy	+/- .1mm	+/- .05mm
Min Lead Pitch	.4mm	.4mm
BGA, Leadless (Bottom Vision)	Yes	Yes
Feeder commonality with higher capacity machines	No	Yes
Software commonality with higher capacity machines	No	Yes

The Selection

While both machines met all of the basic requirements, the MC-400 was chosen over the FVX mainly because it provided an upgrade path to larger machines with respect to software and feeders. These features come at a higher cost, but my capital equipment budget allowed for it. That said, the FVX would also be an excellent pick for organizations on tighter budgets, and with their advanced vision capabilities, I expect both machines to postpone their obsolesence for many years to come.