The next-gen iPhone's slim-jim design may be creating problems for Apple's manufacturing partners that build the device, however.

Squeezing multiple components into increasing thin iPads and iPhones is proving to be a challenge for Taiwan-based Hon Hai, the world's largest contract manufacturer. The lower yields are hurting the company's profits, the WSJ reports.

In fact, shipments of the next-gen iPhone may be delayed if Hon Hai can't improve the yield rate of the handset, which is reportedly "complicated and difficult" to make.

Apple is confident that consumers will embrace the new iPhone as enthusiastically as they did the iPhone 4 -- perhaps even more so. The company hopes to sell 25 million next-gen iPhones by the end of the year, an aggressive sales goal for a device that probably won't ship before September at the earliest.

Then again, Apple has good reason to be confident. It in its fiscal second quarter, which ended March 26.