In contrast to Apple's iMacs and MacBooks which have become progressively more difficult to repair in recent years, the iPhone's repairability score has fared a lot better after quickly improving upon its first incarnation, as noted by iFixit.
iPhones have become taller, wider, and skinnier. But they’ve also become more repairable. The very first iPhone earned a dismal 2/10 on our repairability scale. It had a soldered battery and was almost impossible to open without breaking the case. Repairability improved radically from there — jumping to a 7/10 for the iPhone 3G.Since then, the company's flagship smartphone has remained relatively repair-friendly, earning at least 6/10 on iFixit's repairability rating with every iteration. The most recent iPhone offering, the iPhone 7, was awarded 7/10 on the scale in 2016.
Check out the "10 Years of iPhone" roundup page on iFixit, which also features a neat look at the visual changes the components have undergone over 15 models.